Mesh Cant Flexy?

[Toysoldier Thor]

I created 3 mesh models in the beta grid.  I was playing with some of the mesh parameters....  I noticed that none of the models allow me to enable the Flexible Path.  I thought mesh supports flexi like a real prim.  Is there some trick to making a mesh go flexy?

On another note on newer viewer features in EDIT...

What is the Features called"  Gravity, Friction, Density, Restitution?

[Jenni Darkwatch]

Mesh cannot be flexy, same as sculpts. The additional settings you mentioned affect the physics engine, though I've got no idea what they do in detail.

Edited to add:

Gravity should be, in a sense, the weight of an object (really the force of attraction, though I doubt Havoc has gravitational simulations)

Friction is more or less how "slick" or "slippery" something is.

Density... in the context of SL, no idea.

Restitution is difficult to explain. In physics it's kind of a measure how "bouncy" an object is on impact.

[Kwakkelde Kwak]

Meshes can't be flexible, You'd need two things for that, a hinging point and some sort of weight painting. There's currently no way the engine can determine how the object has to flex. This is the case for most objects, not just sculpts and meshes. Only boxes and cylinders will flex.

On top of that a detailed object (a mesh will be that in 99% of the cases compared to a cylinder or box) would mean a huge load on the system.

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Gravity doesn't mean the weight of an object, it's what you said, the accelleration applied to it when falling. It's a simple formula, I bet the engine does simulate it. I'm not 100% sure though.

Density means what it always means. The higher it is, the heavier your object (compared to its volume). So you will notice this when you apply a force to it (cars, planes etc), when you walk into it or when it hits another object.

 

[Chosen Few]

To expand a little on Kwak's point that only cubes and cylinders can flex, it would probably be useful to explain the why behind how the flex actually works.  Notice its proper name is Flexible Path.  The key word there is "path".   See, all prims in SL are created by extrusion.   Each one starts out as a basic two-dimensional shape, called a profile, which is then extruded along a perenducular line or shape, called a path, to form what appears to be a solid three-diemensional object.  If you bend that path, you effectively bend the object.

Cubes and cylinders can be made flexible, because their paths are just simle straight lines.  A cube is made by extruding a rectangular profile along a straight line, and cylinder is made by extruding a circular profile along a straight line.  If you take that straight path line and let it flop around in the breeze, you get a floppy cube or a floppy cylinder.  The profile shape remains the same rectangle or a circle, always, but the path line is allowed to curve.

The other prim types cannot flex, because their paths aren't just simple straight lines to begin with.  They're circular.  A sphere is an arc-shaped profile, extruded around a circular path.  A torus is a circular profile, extruded around a circular path.  A ring is a triangular profile extruded around a circular path.  If you bend that circle, the end result will look more like a jiggle than a flex.  LL talked about adding "jigglies" not long after flexies were introduced.  But they never actually did it.

The reason an arbitary mesh cannot be made to flex is because it's constructed along entirely different principles than how prims are made.  There's simply no information present to tell the system how to make the mesh deform.   There's no path, no profile, no embedded parametric construction history whatseover.  The shape you see is the shape the object actually is, not just an illusion created by extrusion.  SL has no idea how the arbitary shape might have come into being.  All it knows is the end result.  Thus the shape of the mesh must be rigid, all vertices fixed in place relative to each other.

If you want to make an arbitrary mesh flex, or otherwise deform in any controllable way, you have to bind it to a deformer object, such as a skeleton.  The avatar mesh, for example, can bend 26 different ways, because it is bound to a skeleton with 26 indivudially rotatable bones in it.  It can also morph in about a hundred different ways, because it's got about a hundred blendshapes and other deformers in place that all control the relative positioning of its vertices.

At present, the only way to make a mesh be non-rigid is to rig it to the avatar skeleton, so that when its worn, it will bend and flex as the bones of the skeleton rotate and move. This, obviously, is only useful for wearable items like clothing and body part replacements.  It's not at all useful for anything that won't be worn.

One day we might get the ability to assign arbitrary deformers to arbitary meshes.  But I wouldn't hold your breath waiting for that.  It's a long way off, if it ever it is to come.

[Maeve Balfour]

Thankyou for the enlightenment Chosen - I've often wondered HOW flexi-prims worked. I knew there were complex reasons as to why mesh, sculpts and non cube/cylinder prims couldn't flex, but now I know specifically. The theory and practical implementation behind the scenes is always fascinating to learn!

:matte-motes-smile:

[Toysoldier Thor]

That was very informative Chosen.  Thanks for the background why mesh wasnt and likely wont me flexy path.  Understanding the reason why makes sense... too bad though as Flexy has been a very useful feature to add easy environmental animation to SL.  (i.e. trees flags etc.)

[Medhue Simoni]

Although making mesh flexy is not possible and, most likely never will be, there has been talk about arbitrary bones.

It should also be noted that flexies was kind of a gift. Making things like clothing or objects moving in such ways is something you just don't see much of in any game or even animated big time budget movies. For a virtual world, it's still quite impressive, even with it's limitations.

Daz has dynamic clothing, and people are always asking in video comments how the creator did that.

[Security Huntress]

There is a way to turn on the "Flex" option and setup its parameters by script.

And like what choosen said, there's no "flex" path pre-embeded in the prim/sculpt in the past that allows the system to know "How" to flex the object. So turning on "flex" will return as no result for worn objects, but rezed child objects will somehow turn partly phantom even when linked.

But what others didn't know is the Collada actually do support flex weight painting in their codes so adding a flexi path is not impossible (might have to toy with the axis setting, polygon/face limits to match SL's, before hand). The only thing left is will the SL engine render them as desired or will the uploader itself upload the embeded flexi-path in the dae file is another question.

[Strawberry Lionheart]

I haven't seen any successful case of a flexible path weighted mesh in Second Life so far.

 

What others do is they simply "animate" the mesh with a series of keyframed exported meshes and script them to "move" in SL with script (Just like the old animated sculpts but with a different script). And yes that means you need to export and import EVERY frame needed to be used in the mesh/sculpt animation and for rigged clothing, re-rig every frame before exporting. There is one way to reduce the export numbers by multi-subbing but it will also means a more complex script needed to animate the meshes.

 

And if you are good with script you can control "When" the mesh starts to animate and do "Which" animation pattern according to what the avatar is currently doing.. eg. walking stance, sitting stance, flying stance, idle stance... 

 

Please remember that this method, tho working, is not the best way because it costs a lot of loading time as well as rendering resources... So it's quite the irresponsible way of creating a mesh since they will be the ones that lag SL up a lot. Especially when you are not good with mesh polygon control when you build and ended up with an overly faced mesh.. Animating that kind of mesh will be lag hell for everyone.