Friday, 15 May 2015


I discovered much to my embarrassment that I neglected to include +Neothar Cortex's props add-on "slave" script in the 1.02 packaging...the main add-on controller script is there, but not the one that needs to go into each of the props.

The box version in Hedonism has been corrected, as have any of the other boxed copies I've given to others to redistributte; but if you picked up a copy of the newly released 1.02 system in the first ~12 hours after release the script may be missing. The correctly boxed version will say version 1.02.1 on the box to indicate that it has the extra script.

If you have one of the early versions that is missing the script you can pick up a new boxed one, or (far more easily) simply create a new script and called it "nc_props 1.1.0" (the main props add-on script is called ".addon NC Props 1.1.2" and is the one that goes into the same obect that contains the core script). Put this script in the same folder that the rest of the builder's kit stuff is in, then paste the following script into it:


// props_debug v1.1.0
// v0.1 adapted to send absolute position
// v0.2 added debug switching via description
// v0.3 changed debug output
// v1.0 added debug output for derez on timeout
// v1.1.0 starting to convert into no_listener design
// written by Neo Cortex for use with the PMAC addon NC-props

// Put this script inside any PMAC prop.
// Supports saving the prop's position
// Dies on region restart

key MasterObject;

integer gi_Debug                       =FALSE;
NCDebug(string txt) {
    if (gi_Debug) {

default {
    on_rez(integer rez_arg) {
        gi_Debug = (llSubStringIndex(llGetObjectDesc(),"debug") != -1); // enable debug if object description contains 'debug'

        MasterObject = osGetRezzingObject(); // who rezzed me?

        osMessageObject(MasterObject,"NC_PROP_REZZED"); // tell Master who i am
    dataserver(key who,string msg)
        NCDebug("nc_prop received: " + msg + " from: " + (string) who);
        if (msg=="NC_PROP_DIE") llDie();
        if (msg == "NC_PROP_SAVE") { // report position
            osMessageObject(MasterObject,"NC_PROP_POSITION::" + (string)(llGetPos()) + "::" + (string)llGetRot());
//            NCDebug("Pos: " + (string)(llGetPos()) + " Rot:" + (string)llGetRot());

    changed(integer change)
        if (change & CHANGED_REGION_START) llDie();


Then save. Now you'll have the missing script which is the one that goes into each of the props you want to be able to rez and controll with Neo's add-on.

My most profuse apologies to Neo and to anyone inconvenienced.

Wednesday, 13 May 2015


Announcing the release of PMAC v1.02

This is the first update to the PMAC system and includes a couple small bug fixes, a few minor tweaks, and now introduces the brand new NC Props add-on written by +Neothar Cortex  to allow PMAC to rez and position props in the scene. Great job, Neo!

PMAC 1.02 will now also support the use of a PMAC object by NPCs without a "live" user also being present.

Existing PMAC 1.01 users will benefit from the two small corner-case bug fixes and have a few new handy configuration options. No changes are required to your existing set-ups other than to replace the core script.


  • BUGFIX/OVERSIGHT: added flag so if an addon rezzes an object core is prevented from interpreting this as an edit handle being rezzed and entering edit mode
  • BUGFIX: fixed a bug in edit mode list wrapping where advancing from the last animation in a group using "NEXT" would pull the incorrect data for the next (first) animation.
  • TWEAK: now sets a negligible sit target to allow sitting on it from distances greater than 10m (you should be able to sit from anywhere in the same region)
  • TWEAK: When displaying animation number range in dialog menu, display the actual range instead of possible range
  • NEW: added support for the Object-Rezzing prop add-on "NC_PROP" by Neo Cortex (code from Neo)
  • NEW/TWEAK: Altered script logic to optionally allow NPCs to occupy a PMAC object with no "real" avatars being present and added a user configuration variable to enable or disable this feature. By default it will be set to FALSE. If the NPC is to be rezzed by another object/script that script will also need to handle seating it, later unseating it, and removing it from the scene. Initially rezzing a PMAC NPC still requires an avatar user but if that user stands when NPC flag is TRUE, the NPC will not be removed (I'll need to sit down again and remove it). Be careful NOT to reset the core script when a PMAC NPC is still in the scene since this will strand it.
  • NEW/TWEAK: Added new user option to show the groups menu instead of the current group's animation menu when you first initiate the dialog. Subsequently if you close the dialog and re-show it, you should received whatever your most recent dialog was unless someone else was in control in the interim.
For full details of all of PMAC's may other features, please see the initial release announcement.

Pricing and Where to Get It

It's completely free! PMAC is distributed under Creative Commons Attribution-Non-Commercial-ShareAlike 4.0 International license and is full-perm.

The full builder's kit version, boxed, is now available in the lobby of my Hedonism Club at and will very soon be available also at Nara's Nook, OSGrid's Wright Plaza, and several of Dorothea Lundquist's stores in OSGrid. Anyone else wishing to make the full boxed kit available in their own stores should contact me for a copy. This contains all of the necessary core components, documentation, the MLP-to-PMAC converter written by +Seth Nygard , the Props add-on by +Neothar Cortex and the Expressions add-on (written by me)...everything you need to enter the next generation of multi-avatar animation controllers.

Saturday, 9 May 2015

Blender: Introduction to My Beginner Level Tutorials and an Overview of Blender Primitives

Having now covered most of the key novice-level Blender subjects, I intend to begin my next series of tutorials which will approach a variety of subjects that I think of as being "beginner" level and would be typical in the workflow for creating many of the items you're likely to work on as an Opensim content creator.

Today's "tutorial" is more of a quick overview of what I'll expect you to know before doing one of these new tutorials as well as an overview of the basic classes of Blender Objects.


To save myself from endless repetition of basic instructions which would interrupt the flow of the tutorials and make them excessively lengthy (to prepare and read), each of the tutorials at this level will assume that you've either read through my novice level tutorials or are reasonably familiar with their content, and that you've subsequently done a little bit of experimentation on your own to learn the most basic modeling techniques (transformations and extrusions).

Specifically, they'll assume that you're somewhat familiar with the Blender interface and have a grasp of the basic core selection and modeling techniques used to build and manipulate mesh geometry:
  • know where to find each of the key panes that content creators typically use (Info (main menu bar) pane, 3D View pane, Properties pane, UV/Image Editor pane)
  • know a little bit about the primary modes (Object, Edit, and perhaps you've played a bit with Sculpting mode too)
  • know how to add mesh objects to the scene (plane, cube, etc)
  • know how to do basic transforming of objects in Object mode (move, scale, rotate)
  • know how to select and transform parts of objects in Edit mode (faces, edges, vertices)
  • know how to extrude one or more faces,edges, or vertices
  • know how to make a loop cut
  • know how to subdivide a mesh in Edit mode
  • know how to create a material (using Cycles Render engine) and apply it to specific faces of a mesh
  • have a very basic understanding of what UV-mapping is and a bit of novice-level experience with marking seams and unwrapping an object using the "Unwrap" method.
I'm not expecting you to be expert at any of the above, simply that I can include those as part of these tutorials' content without needing to give step-by-step instructions or explanations that detail them.
 That will make it considerably less time-consuming for me to prepare the tutorials, and make them shorter and easier for you to subsequently read.

Primitives (as a Blender Term)

You're undoubtedly familiar with the word "primitive" from your Opensim building experience and you might be unsurprised to find the word used in Blender, too, since it's a common term used in the 3D modeling world. It carries a similar meaning but with a broader scope than you've encountered in-world.

In Blender, there are a variety of "classes" of primitive and only one of those classes, "mesh," corresponds to your in-world experience. As a content creator these will be the ones of greatest interest to you since they're the only ones you can actually import in-world; but to take advantage of the full power of the software you will often need to use primitives from the other classes as part of your workflow. Some are aids to allow you to manipulate your mesh, others are converted into mesh after working with them in their non-mesh form, and still others are used (rarely) for other special applications.

The goal in today's tutorial is to briefly introduce you to the range of Blender primitives and give you a rough idea of what they're used for. Future tutorials will use objects from those classes so it's helpful to know a tiny bit about them first.

If you start Blender with a completely empty scene in Object mode and look at the 3D View Toolshelf's Create tab, you'll see buttons for many of Blender's primitives. There are a handful of additional ones that don't have buttons because their application doesn't make a button useful or they're used somewhat less commonly; but if you want to peruse the complete list simply click the "Add" menu option in the 3D View's menu bar since every single item in that menu and it sub-menus is a primitive.

When you look at either listing, you'll see Blender groups them into classes of primitives that share very similar characteristics. In fact even the classes are arranged into six overall groups which don't have official names but you'll see them separated that way in the menu. Here are my mental names for them, starting at the bottom of the menu:
  • Things: All of the classes in this, the largest group or primitives, are ones that are either meshes or are usually later converted into meshes. Of prime importance to the content creator are the first two: meshes and curves. We'll talk more about this group a little later.
  • Manipulators: The three classes in this group are generally used to manipulate the primitives from the Things group but can't be converted into meshes or imported. All three can be of critical importance to a content creator so we'll talk about them in a bit more depth later, too.
  • Speakers: This single-class group is of absolutely no interest to an Opensim content creator and can be completely ignored.
  • Visual: This group contains cameras and lamps which will be of increasing interest to content creators as they become somewhat more expert in Blender. They are an essential part of some texture-generation techniques that have a direct impact on the way objects appear in-world but are best left to a more advanced level of tutorial. You can get a taste for them as a component in +Chic Aeon 's recent set of Cycles tutorials.
  • Physics: Although this group only contains one class of primitive, Force Fields, it is the gateway to an entire element of Blender that can be of intense interest to more advanced content creators. Blender's core contains the Bullet physics engine with many (many!!!) more of its aspects full implemented. Force fields act on primitives from the Things classes to make them behave as their real-world counterparts would behave. Although intended primarily for uses that can't be exported to Opensim, they can be extremely useful as tools to improve the realism of a mesh. For example, I will usually run a gravity-based cloth simulation on mesh clothing to have it drape more naturally on my body, then apply those results to my mesh. That's a technique that I'll talk about in a different (advanced) tutorial sometime.
  • Grouped Stuff: Generally speaking this group isn't of much interest to content creators who are usually making one-of objects that will later be duplicated and positioned in-world, instead. If you were building entire scenes in Blender you might find this of more use, or if you purchase the Avastar add-on for Blender you'll find it listed in this group.
At our beginner level of tutorial, only the first two of the above groups are of much importance so let's spend a bit of time looking a little bit more closely at them and their classes.

These Are a Few of My Favourite Things

Gratuitous Sound of Music reference aside, the "Things" group of primitives is your go-to place when you're first starting out so it's certainly going to be your favourite (it probably already is). The Things group contains five classes and all but one leads to a sub-menu with a variety of primitives to chose between. All primitives of any class in this group can be converted into mesh (if they aren't already mesh) and exported to be brought in-world.
  • Mesh: the bread and butter objects you'll be working with all the time. This is the class that corresponds to the in-world "prim" you're used to but has a few more alternatives for you to choose from because in Blender we frequently begin modeling from a 2-dimentional starting point (plane, circle).
  • Curve: this class is the other very important one in the Things group and will probably become one you use quite often. Curves are easy-to-manipulate objects that can later be converted directly into meshes, saving a lot of time and trouble trying to model an equivalent object by hand.

    Curves have an additional, incredibly powerful use that would make them just at home if they'd been placed in the Manipulators group of classes instead, since they can be used to manipulate and modify a regular mesh object, usually using the "curve modifier."
  • Surfaces and Metaballs: these two classes are are curvy ways of making and manipulating mesh-type 2D and 3D objects that, for some projects, might be a more convenient starting point instead of their mesh equivalents. Once shaped as desired, you can convert them into mesh for further work. I don't use them very often for my own work but there are the occasional projects they're very useful for.
  • Text: this is a primitive that doesn't belong to one of the other four classes so it's listed by itself. If you need to model 3D text you'll usually want to use this. Be warned, though: mesh text usually has a very high poly count.
In almost all cases you will begin a project working with a Mesh or Curve (or combination). Later, you might add a primitive from the Manipulators group...


This second group of primitives are ones that you can't convert to into mesh so they'll never be making an appearance in-world; yet they're extremely useful and powerful and will likely become part of your workflow as you become more experienced. I call the primitives of these three classes "manipulators" because that's exactly what they're used for: manipulating the primitives from the Things group.

This manipulation is usually accomplished by adding one of these primitives to a scene that already contains an object from the Things group, then assigning a modifier to that thing which uses the manipulator primitive as the object that controls the way the modifier is applied. I'm sure that doesn't make a lot of sense when read in isolation and when you've never worked with them before, but as you work your way through my other existing (and forthcoming) beginner-level tutorials you'll fairly quickly come to understand what I mean.
  • Armature: it's unlikely that you'll ever add something from this class directly unless you become an extremely advanced user; but if you get into making mesh clothing or creating animations, you'll use a pre-made SL-based armature as an element for all of that work. The armature is a collection of  "bones" that make up the animation structure inside your avatar and "manipulate" it by moving it in-world.

    If you ever wanted to make an armature from scratch, the bone primitive found here what you'd use to build it. Then you'd use the "armature modifier" to link it to one or more primitives from the Things group and then subsequently manipulate them.
  • Lattice: this is an incredibly useful primitive that is used in conjunction with the matching "lattice modifier" to manipulate the shape of Things without having to do all of that modeling by hand. I use it extensively to help fit and adjust clothing, and for large-scale modeling and contouring or objects (usually non-geometric ones).
  • Empties: this is an oddly-named class that contains a variety of primitives. For the most part you'll only use "Plain Axes" one in conjunction with the "mirror modifier" or "array modifier" although there are other instances when it can be useful.

So What?

I've done a lot of "talking" but not any "showing" of these things we've been discussing, so you're probably wondering when I'm going to get around to that so you'll begin to have some idea of what the heck I'm going on about. I've already done that, without looking at it from this "overview" perspective, so armed with the above information you might now want to revisit a few of the very first tutorials I posted to this blog. Each of those is very simple and will take only a short time to complete, yet demonstrates the power and flexibility of controlling Things using Manipulators and modifiers:
  • Fun With Blender Arrays was my first blog post and will show you a "Thing" primitive that is then given an array modifier and, a bit later in the tutorial, a "Manipulator" Empty prim is added and used to make a very interesting and complex pattern from just a very basic torus.
  • In More Fun With Blender Arrays I again show how powerful the Empty manipulator prim can be when used as the controller for an array modifier applied to a simple cube to make a spiral staircase.
  • In the third post of that series I show how to take a very simple torus primitive, then use a curve primitive and an empty primitive to make a curved chain.
  • Chains Revisited shows the lattice primitive used with the lattice modifier on a simple torus, the shaped using a curve primitive into a necklace using the array and curve modifiers.
  • In the Screwing Around tutorial you'll see a curve used as a very easy way to rapidly shape an object which is then converted into a vase after applying a simple screw modifier.
Hopefully those will whet your appetite for the entire series of modifier tutorials I intend to prepare over the coming weeks to introduce modifiers in general, and then take some time looking at each of the ones I consider to be most useful for Opensim content creation.

Monday, 4 May 2015


If you are currently using PMAC v1.01 you should be aware the I am in the process of making a few updates in preparation of releasing PMAC v1.02. I anticipate releasing the new edition sometime in the next 7-14 days.

Change log (not yet finalized) for 1.02

  • NEW: PMAC builder's kit will now include the new NC_PROP addon scripted by Neo Cortex which has the capability of rezzing props specific to each pose. This was a core element of MLP and is relatively common so I felt that making the necessary changes to PMAC core to support it was warranted. I'd like to extend a huge thank-you to Neo for this excellent community contribution!

    There is not yet a parsing utility to convert an MLP prop setup to a PMAC one (and it might not be possible to do so due to some configuration/command differences) so the intial setup will have to be done manually, at least in the short term. Perhaps some brave soul will tackle that side of things?
  • BUG/OVERSIGHT FIX: fix the case where a script in the object containing the core script rezzes an object to prevent core from misinterpreting the event call and entering edit mode.
  • NEW/TWEAK: I received requests from several people to allow PMAC to be used by NPCs even if no "real" avatar was still present, including allowing an NPC (rezzed by a different controller) to sit and activate PMAC from its dormant state even without an avatar being present. This will be added as a user setting with TRUE/FALSE flag. If you set it to TRUE to allow NPCs to be there by themselves, it's up to you to remember to remove them when/as necessary either using PMAC's menu or via an external script. I am still testing to ensure this doesn't break anything in corner cases.
  • TWEAK: on state_entry() PMAC now sets a tiny sit target which will now allow you to sit on it from anywhere on the sim instead of having to be within 10m of it. I don't know if the 10m limit is an intended restriction for objects that don't have sit targets or whether it's an Opensim bug...either way, this was a change that was requested and seems reasonable.

None of the changes will invalidate or affect an existing setup. All existing set-ups will remain 100% compatible with 1.02 script with no alterations and there will be no urgent need to update to 1.02 unless you wish to take advantage of the new stuff or tweaks.

If there are any tweaks you'd like me to consider, or bugs you've discovered but haven't reported to be yet, or other things you want me to think about including/changing in the 1.02 release, now is the time to communicate them to be so I'll have time to do so and properly test them if they're feasible.

Barring that, look for a release announcement in the next week or two.

Sunday, 3 May 2015

Blender: Out of the Frying Pan and Into the Fire

This final installment of my novice set of tutorials covers the subject of getting your models out of Blender and into Opensim. This is what distinguishes us from the majority of Blender artists: we are only using Blender as a step in a creative process rather than using the software to produce our finished products.

There are four steps involved once you've finished modeling and you're ready to export your object:
  • Prepare the model for export
  • Do the actual export to Collada (.dae) format
  • Import the object into Opensim
  • Rez the object and get it to look the way you want it to in-world
For the purposes of this tutorial I will be assuming that you have UV-mapped the object you want to export and assigned at least one material to it.

Preparing a Model For Export

If you follow the recommendations I've made earlier in this series, the majority of your models will be made up almost entirely of quads which is (by far!) the optimum method when working in Blender. Opensim (and SL) only allow us to import objects made entirely of tris; so before we can export something we need to convert all of our quads (and perhaps a handful of n-gons) into triangles. We can do this quite easily in one of three ways and I'll show you all three methods.

Actually, there's a fourth method but nobody in their right mind would contemplate it for anything other than the most simple, basic objects. You could, if you were really patient (and insane?) go in and do it by hand, manually creating the diagonal edge to divide each quad in half.

With a very, very simple mesh model like the monkey Suzanne this would involve manually selecting about 500 faces, one by one, and for each of these you would need to decide which pair of diagonally-opposed vertices to connect to turn the face into a pair of triangles. Needless to say, this isn't something we'd ever want to contemplate doing. It is instructive, however, to think about that operation for a moment though, since that's exactly what we're going to be asking Blender to do for us.

For any quad there are two different ways to "cut" it into a pair of triangles, and unless the quad is perfectly flat and rectangular the choice of which of those two diagonals to use can be quite important. Let's spend a moment looking at that.

In an empty scene, add a simple mesh plane using the default values, then switch into edit mode. We'll do a side by side comparison so we want to duplicate it. With the entire object selected use the hotkey combination SHITF+D X 2.5 (Shift+D duplicates the selection and automatically actives the grab -- move -- action so we follow that up by telling it to move along the x-asix by 2.5m).

Now in vertex select mode on the left hand plane select the back left and front right corners then press the hotkey J to join the two vertices with an edge. For the right hand plane, select the front left and back right corners and J to join them as well.

We don't see any difference at all between our two identical "triangulated" planes because they're perfectly rectangular so let's change that a little bit. Select the two rear vertices of one of the planes which will select the rear edge (we're going to do the same thing with both so it doesn't matter which plane you do first) then use the following hotkey sequences:

  • S 0.75 (scale the edge to 75% of its previous size)
  • G X -0.1 (move it -0.1m on the x-axis)
  • R Y 10 (rotate the edge by 10 degrees on the y-axis)
Now select the two rear vertices of the other plane and repeat exactly the same sequences. Now switch back into Object mode (the picture below is still in edit mode) and look at the planes as you pan your view around them..

As a quad, these two planes are identical because the four corners are in identical locations; but the effect of "triangulating" it manually (cutting it into two triangles results by connecting one of the diagonal pairs of vertices) has quite a different visual effect. The quad on the left now looks like it bends a bit downwards whereas the one on the right looks like it bends a bit upwards.

In Object mode, on the Toolshelf's Tools tab, look for the two buttons in the Shading section called "Smooth" and "Flat." By default the plane is created with all-flat normals so click the "Smooth" button which will now use a built-in algorithm to try to make the surfaces appear smooth (see the Context III tutorial for if you don't remember what normals are). You'll probably find the two planes are almost indistinguishable although you might see a slight difference if you look extremely carefully. Now click "Flat" to return to having the normals calculated independently for the two triangular faces of each plane and the visible crease will reappear.

Now consider this: each quad face of a mesh has to be cut in half just like we've cut our plane in half so when we're asking Blender to do it for us automatically it has to figure out which of the two diagonally opposite corners to connect and there will be a distinct visual impact from Blender's decision, although this will be far more noticeable for portions of meshes where the faces are using flat normals and much less visible for portions that are smooth.

Now that we've seen there's a tangible difference in the way we triangulate a quad, let's see a more representative example of this effect in action. Thankfully, Blender gives us the mesh monkey Suzanne to play with was we look at things like this. Let's pretend she's our finished model that we want to export and upload to Opensim.

Either pick a different layer to add her to, or delete your simple double-plane object, then add a new mesh monkey. While you're still in Object mode, click the "Smooth" button to make Suzanne appear to have a fairly smooth surface. You'll still see some areas where she doesn't look very smooth but that's because she's a very low poly model for this sort of complex organic shape (only 500 faces). You could greatly improve her visually by modeling her at a higher resolution, but this significantly increases her poly count and therefore the file size for her mesh. Modelling for Opensim is a constant battle between improving visual quality versus keeping the file sizes small enough to transfer quickly to a visitor's viewer so they can see it.

Now switch into Edit mode (Tab) and you'll see that Suzanne is modeled almost entirely using quads, with only the central faces of her eyes being tris. To export her for use in Opensim all of those quads need to be tris, so we need to divide every single one of those faces into two triangles by connecting diagonal corners like we did with our plane. Now we can talk about the three viable methods for doing this operation since, I presume, you're not going to be interested in trying that fourth method of doing each and every one of them, one by one, manually.

The least preferred method for "triangulation" is the one we'll cover this first. While still in edit mode, ensure that the entire monkey is selected and then use the 3D View pane's menu to do Mesh > Faces > Triangulate Faces. (We could just have used the hotkey combination "Ctrl T" but since this isn't something you'll be doing all that often it's one that you probably won't remember so it's better you know where to find it in the menu.) This tells blender to automatically turn any faces that are currently selected and aren't already tris into tris. Any face that is already a tri will be left untouched. As soon as you do this you'll see that Suzanne's faces have all now been triangulated for you.

Before doing anything else, look at the Most Recent Actions area of your Toolshelf where you'll now see a pair of drop-downs containing the options for triangulating faces. One tells Blender the method to use for quads, and the other tells Blender what to do with polygons (the formal name for ngons which have 5 of more edges). By default, both will have used the "Beauty" method.

Suzanne doesn't have any ngons so the only one that actually has relevance to us is the quad method so now let's use the quad drop-down to select each of the four options, one by one to see what they do. Suzanne will be automatically updated to show the effect of the choice because until we do something else our most recent actions options are still modifying our "triangulate faces" action. Our choices are:
  • Beauty: this lets Blender try to figure out the best method for each face, separately, to try to produce the most visually pleasing result. I use this most of the time since whatever internal algorithm Blender uses to accomplish this is usually pretty good at it. The Blender documentation warns us that it's the slowest method to use, but since our models for Opensim need to be kept to a reasonable size, I've never noticed any appreciable delay in the operation. If you had a model with millions of faces, each of which had to be "calculated" for beauty, it would get slow -- but you'd also never be able to get it in-world.
  • Fixed: Blender's documentation says this connects the "1 and 3" corners of all faces, but it's a little more than that because it's also aware of symmetry on each axis. I only use this method in very rare cases for specific objects where I need each diagonal to be aligned with one another, usually as a convenience step prior to doing additional modeling work.
  • Fixed Alternate: is identical to Fixed except it connects the "2 and 4" corners so is the mirror of Fixed. Again, I only use this method on very, very rare occasions.
  • Shortest Diagonal: this tells Blender to measure the distance between the opposing corners of each face and create the edge based on whichever distance is shorter. I use this one somewhat frequently when I have a model that is extremely thin (usually as a result of "solidifying" it) since the beauty method can sometimes result in the newly created edge on one side intersect an edge from the other side -- something that can cause visual issues in-world and greatly increases the chances of problems calculating the mesh's physic on upload (see below). I also find that this method tends to produce better results for a highly geometric, round shape like a sphere or torus.
There's rarely any "best" method to can usually just go with whichever one looks the best on your screen. Most often that will be the default Beauty method.

I call this the least preferred method because you have to do this manually, one at a time, with each object in your scene; so if you're exporting a linked group of objects it will take some time to go and do this for each one. Also, you don't want to save your blend file like this because if you later want to come back and make changes to it you'd have tri faces instead of quads, making it much, much harder to work with.

The one significant advantage it does offer, though, is the ability to select only some of the faces of a mesh, then triangulate them using one method, then select other faces and triangulate them using a different method, and so on. If you need to do this for some reason, try to be sure that you also have an archived quad version of the file just in case you need to come back to it again later.

Once you've had a look at the result of all four methods, use the Ctrl+Z hotkey combination to undo the triangulation and return Suzanne to her quad-modeled state so we can look at a second method.

The second and usually "best" method is to use something called a "modifier" on our object. A modifier is something we assign to an object that will perform an action of some sort to the mesh based on its settings, but doesn't actually do the action until later, when we tell it to. This allows us to preserve our model exactly as it is, but set up something to "do later" that will affect it. I won't go into any more details about modifiers since that's a subject for a whole series of beginner-level tutorials. For the time being I'll just show you how to use one for what we want to do.

First, switch back to Object mode and ensure you've selected Suzanne, then on the Properties pane look for the tab with a small wrench symbol called the "Modifiers" tab. When you select that tab the rest of the Properties pane will be blank except for a drop-down box where we can "Add Modifier."

Click the drop-down box and you'll see an enormous list of the possible modifiers we can add to Suzanne and the one we want to use is called "Triangulate" which is near the bottom of the second column of options (the set of "Generate" modifiers).

Once you've selected this you'll see an entry appear in the Properties pane that tells you that you're adding a Triangulate modifier and then has a number of options associated with it. I won't explain the meaning of all the little icons across the top of the modifier's entry other than to mention that you'll only see the effect of the modifier on your screen when the eyeball icon is selected (which it will be by default). What we're interested in are the settings options in the main part of the modifier.

You'll see that the modifier settings has a pair of drop-down boxes that are identical to the pair of drop-downs we saw earlier when used the first method to triangulate Suzanne. Whichever one you select for quads, here, will result in the identical change to Suzanne's quads that you already saw earlier.

The difference is that until you click the button labeled "Apply" Suzanne's actual mesh isn't changing. We're just setting up a handy little button for us to click any time later to automatically triangulate her according to these settings. Clicking "Apply" will do exactly what it says: apply the modifier to the object and therefore change it to be all-tri faces. Don't do that yet, though, and if you did you can always Ctrl+Z to undo and restore the mesh and modifier.

When you save the file, Blender saves any modifiers along with everything else, so if you later want to come back to edit the object, you'll still have your nicely preserved quads and a handy modifier set up. If you have multiple objects in the scene, you'll need to give each one a triangulate modifier, but you can use different settings for each different object if you wish to.

You can add a modifier to an object at any time so you don't need to wait until you're ready to export before you do this. In fact, I typically add a triangulate modifier to each new object when I create it, just so I don't forget to do it later. Unless you "Apply" it, the model is unaffected and while you're working it lets you continually preview how the model will look after triangulation.

The only disadvantage of this approach is that modifiers apply uniformly to the entire object so you don't have the ability to use "Shortest Diagonal" for only some faces and "Beauty" for others. You can only use one method for all quads and, if desired, a different method for any ngons your model might have.

The third method is to triangulate the entire export at the time of export so let's move on to that step now.

Exporting Your Model(s)

Before doing anything else, save your (.blend) file so you'll have a copy of it to come back to.

Now select the object you want to export. If you want to export multiple objects at once, you can SHIFT+select them to add them. This will create a linkset when you import with each of your individual objects being one of the links in the set (and behaves exactly like linksets of prims and/or sculpties).

From the main menu at the top of Blender's screen select File > Export > Collada (Default) (.dae) which will bring you into a screen that is almost identical to the one you see when saving a .bllend file.

Supply a name for the file to export, making sure you keep the ".dae" at the end of it and I strongly recommend saving the dae to the same folder your .blend file is in.

Now look at the lower left side of the screen where you'll see a number of (very poorly documented) export options.

You want to be sure to check the option to "apply modifiers" and ensure that the "View" option is chosen from the drop-down. If you're using method #2 for triangulating your meshes this will automatically apply each of them first, which is what we want to have happen. The "View" part isn't relevant to the triangulate modifier but is for others and you'll always be using the view option.

You also want to check "selected only" to tell Blender that it's only the object you've currently selected that should be exported to the Collada file. The other three options here aren't ones you'll need to worry about until you're doing considerably more advanced work.

In the textures section make sure your "only selected UV map" is checked so maps are only exported for the objects we're including in the file. If you check the "Include UV textures" option a copy of your textures will be saved in the same folder and linked in the file. If you haven't made any textures for it or have already uploaded them and will apply then in-world, you can leave it unchecked. Usually (but strangely, not always) having it checked will then upload and apply your textures automatically when you import them in-world but I still haven't figured out what causes that to fail at times. See below for more about that.

You can ignore the armature section until such time as you're working with rigged mesh clothing or custom mesh avatars. For regular objects these options don't apply.

The third method of triangulating everything is by checking that option here in the export settings, and even if you're positive that everything you're exporting is already triangulated or has a triangulation modifier it's still not a bad idea to check this too. It won't alter any tri faces and just in case you forgot something it will catch any quads you might have missed. I am not certain whether this uses shortest distance or beauty as the method but I suspect it uses shortest distance. We're just making sure that all objects being exported are getting this last "safety check"  to ensure they're Opensim compatible meshes.

I have some doubts about whether the "sort by Object name" option matters at all. Supposedly if you have multiple objects selected the Collada file will have them sorted in alphabetical order which should then result in the first of those being the root object of a linkset. In practice this doesn't seem to be reliable so I always assume that the root will be assigned randomly and I might need to rez the set to ground, unlink the part I want as root, then relink it into a set with the desired root.

I wish I could offer more assurances about the above, but the documentation is sketchy (or non-existent) so all I can say with any certainty is that these are the settings I use and produce files I can reliably upload.

Import the Object(s) to Opensim

Now the we have our Collada (.dae) file we can close Blender and log into Opensim with your viewer of choice. As far as I know, all TPVs use the identical (or nearly identical) mesh import layout that Linden Labs developed for their own viewer. Yours might have a different skin or slightly different layout than mine but should have all of the same options on the same general layout. My screenshots are made using the current Firestorm 4.6.9 (42974) 64-bit with Opensim support although I believe there's a new version coming in the not-too-distant future but I don't expect this part of the viewer to change.

Depending on your viewer, accessing mesh upload will be a little different (in FS it's Avatar > Upload > Mesh Model, while in other viewers it might be under the build menu instead) and after selecting this you'll be asked which file to upload. Select the one you want to import and once it has finished loading your file into memory you'll be presented with the Upload Model window.

The Second Life documentation for upload is accurate for Opensim, too, so there isn't much point in me repeating the information here other than to add some annotations.

Level Of Detail Tab

At the top, the model name you supply doesn't need to be the same as the file name. Whatever name you use will be applied to all objects that are part of aan linkset you upload -- the original Blender object names are not preserved. The "This model represents..." dropdown is utterly meaningless (and ignored) for Opensim import so you don't even need to bother changing it.

The four LOD settings are something you should pay attention to but are beyond the scope of this tutorial so for the time being use the default values. I will details the issues involved in LOD in a future beginner-level tutorial.

Do not check the "Generate Normals" option since I find it highly unreliable and you should be making any and all adjustments to your normals in Blender, not in the limited interface for a program that isn't designed to make normal-calculations.

Physics Tab

Physics is another subject that requires a whole tutorial series of its own, and is a somewhat more advanced subject. As a beginner you can select one of the options in the drop-down box in step 1 of the tab. For anything you intend to wear, or will be made phantom in-world, or is relatively small and doesn't require much accuracy for collisions in-world, use the lowest setting. For larger objects that will need some measure of collision accuracy when interacting with other physical objects or avatars, you will need to use a higher level of detail. You'll see a preview of the "physics shape" in the preview window which can help you decide which to use but only treat this as a (very rough!) approximation.

For Opensim uploads everything else in this tab is ignored so you don't need to analyze or simplify because they have utterly no effect on your upload.

Upload Options Tab

Unless you start working with rigged mesh avatars or clothing, the only thing you need to do in the third tab is check the "Include textures" box. If for some reason you modeled at a different scale to the one you want to use for import you can scale it here (but it's usually a lot safer and more accurate to do your scaling in Blender).

In theory, checking the "include textures" box is supposed to automatically upload and apply any textures that the Collada file specifies for any material, provided the texture file is in the exact same directory as the Collada file. If it's in a subdirectory or different location, it won't. If you haven't assigned a texture to the material but have assigned it a colour (in Blender) it will usually import with that colour (but again, mysteriously, not always). I've talked to Opensim developers who assure me that their end of the code supports the data as long as the viewer sends it, so all I can assume is either a miscommunication between viewer and Opensim, or some mismatch in the Collada file formatting Blender uses to save vs the one the viewer expects to read.

The Incredibly Annoying and Unpredictable Calculation Step

While all viewers can experience this problem once in a while, Firestorm appear to be highly prone to getting "hung" when you press the "Calculate weights & fee" button. For more complex models I don't even bother trying the upload with Firestorm and will do it with Singularity or Kokua instead.

For personal reasons I prefer Firestorm as my in-world viewer for everything else so I'll often try it just in case it works, but it sure would be nice if they addressed this bug (/rant one that I reported to their Jira more than a year ago and, to date, remains  unresolved and has never had a response from a developer even though the bug itself has been confirmed by their staff. /end rant).

If this button doesn't change into a "Upload" button after a relatively short period of time you may need to cancel the upload and try again. With complex models or large linksets this calculation can take several minutes but for a simple model like Suzanne it should only take a second or two. /more rant If you have to cancel and try again, Firestorm will not release the processor that's being used for the calculation even though you've cancelled it. The only way to get that core back is to shut down -- which will often crash or take many minutes to stop the process -- and restart the viewer./end rant

Barring problems, you can click the "Upload" button and the viewer will repeat all of the lengthy calculations (why it doesn't cache the results, instead, is a complete mystery to me) and add the object to your inventory. If you've included textures they'll be uploaded to your inventory as well.

Rez and Finish the Object(s)

I'm going to assume that you all have sufficient familiarity with building in Opensim to know how to rez and texture objects. If you included the textures in your original dae and upload they should be pre-applied to your object when you rez it. On occasion this will fail for mysterious reasons and you'll have to upload and manually apply them instead.

As long as the object was UV-mapped, each material assigned to an object becomes a "SL face" that you can select and texture exactly the same way you do with a prim. If you didn't UV map the object for some reason you will need to cross your fingers and switch from the default mapping to planar mapping in your viewer's Texture tab and, if you're lucky, it might look okay. As often as not, though, it will look about as horrible as my picture of unmapped Suzanne does here.

Suzanne in-world (model was NOT UV mapped)
A single mesh object can be scaled in any direction just like a regular prim or sculptie. If you combined multiple objects in your .dae they'll import as a linkset -- with a seemingly random selection of root -- and will behave just like a regular linkset, including the ability to unlink it, etc...(each mesh object of the set is actually imported as a separate object and combined as a linkset when it's placed into your inventory).

What Now?

There is no substitute for practice and experience. Unless you spend some time working with Blender (or any complex program) on a regular basis you won't develop the necessary skills and familiarity to take that next step in your mesh-making career.

I have already posted some beginner level tutorials and will be adding more over the coming months to cover some subjects that may be of interest. There are also many excellent tutorials available, both text and video, just via some googling.

Start with simple, highly geometric shapes that would be easy to build using simple prims instead. Normally if you can build it with a reasonable number of simple prims, you should, but as a learning exercise that's a very good place to start. Don't build it exactly the same way, though. Learn Blender's set of basic modeling tools that allow you to construct the entire thing as a single object rather than as a large linkset of prims. That's one of the biggest advantages of mesh.

Once you're comfortable with things like loop cuts, extrusions, and basic modifiers, and basic UV mapping, start working on more organic, naturally-shaped objects which are quite a lot harder to model (and impossible to do with prims). Trying to do these sorts of objects before you've mastered the basics can be extremely frustrating since you'll rarely be able to achieve what you want -- or at least not in a reasonable amount of time.

Learn from your failed attempts. They're just as instructive as -- if not even more instructive than -- your successes. If something doesn't work, figure out why since this will often suggest a better approach to use for that type of object next time.

From a personal level, many moons ago I first learned a lot about prim-building by getting freebie copies of other people's objects and taking them apart to see how they were made. I did the same thing with Blender by downloading a number of the free .blend files for objects that interested me on the BlendSwap website (registration is free, most models are CC licensed, and you are restricted only by the total MB of downloads you can make in a 30 day period without a paid membership). I would then open these files to see how the models had been made, and to try to manually duplicate them myself (even though it's very tempting just to upload the other person's work). BlendSwap is only
one of many sites where you can find free models and Blender is able to import almost all common formats.

Ask questions. There are increasing numbers of people in Opensim who work with mesh and, for the most part, they're happy to share tips and explain techniques as long as you've at least made some attempt to learn the basics. It's to everyone's benefit in the community for there to be many more creators who can add mesh to their arsenal.

Mesh isn't better. It's just a tool. If you need a simple prim cube, rez a prim cube. Don't make it out of mesh just for the sake of being able to say that it's mesh. Things you make using mesh should usually either be shapes you can't achieve using prims, or are highly inefficient to make that way. (Side note to militant prim-only builders: mesh isn't worse, either...honestly! I'll take my "13 prim" single linkset Roman bath building any day over the many hundreds of prims it would take you to get somewhat close to the same appearance)

In time, you can make something like this.
There are no prims in this build and the building (including columns, murals, roof, etc
but not including small furnishings) is a 13-object mesh linkset totaling under 200k faces.
I could reduce this count significantly by going to a different style of column but this build
is intended for personal pleasure and visual opulence, not high volume (or impatient) traffic.

Avatar and clothing are mesh, as well. Hair is flexi-prim and sculptie because I suck at making mesh hair.