Why can't the software just detect collisions between mesh clothing and the shape?

[Jennifer Boyle]

 and alter the shape of the mesh clothing to conform to the shape?

I do not understand the technical aspects of how mesh clothing works.  However, I have a basic understanding of how computation works.  Based on that, it seems like it should be entirely possible for the software to detect collisions between mesh clothing and the avatar shape and gaps between the avatar shape and mesh clothing.  The software knows the shape and position of the avatar.  It knows the shape and position of mesh clothing.  Why can't it compute for each point on the mesh clothing whether it lies inside the shape, away from the shape, or just touching the shape, and alter the shape of the mesh clothing as needed?  Why are bones even needed?

Sorry to ask what must appear the the cognoscenti a stupid question, but I really am curious about this and would appreciate informative answers.

[Masami Kuramoto]

It is possible but computationally expensive. There are ways to use modern graphics cards to speed up physics-based cloth simulation, but these are not available to most SL residents. (LL collects such hardware info for statistical purposes.)

[Kwakkelde Kwak]

Like Masami said, it's possible but very hard on your hardware. NVidia has a system for a good couple of years now that includes real time cloth simulation, called PhysX.

A good place to start reading about the subject might be the development page of APEX clothing (part of PhysX). The last video on the page shows a MMOG using the system.

If you don't mind a long read...

Or just google "real time cloth simulation"

As far as I know APEX works with OpenGL and the latest versions work better on CPU's. I think that last part is very important, since a good part of the SL community doesn't have a fancy video card and has no intention of acquiring one. Another big issue will most likely be the fact that it took years to develop. A similair system would have to be integrated into the SL engine, so that would take a huge amount of LL resources.

It's also far from a magic fix for clothing. I'm not sure, but I think it is just an extra layer on top of all the rigging and painting etc, not a replacement. So although it would definitely improve the looks, it would mean more work for the builder, not less.

[Sassy Romano]

It goes without saying that what we would *like* is this result

but as others have said, to get that to render in the likes of Marvelous Designer, takes a while for the simulation to complete, during that time it is calculating all the positions of the various vertices, how they interact, what collides with what and then it's saved ready for playback at normal speed.

Same reason that we don't have flexi prims that are collision based.  It's one thing to calculate the path of the flex, totally another set of calculations to then take into account all of the objects and their vertices nearby and what influece that would have.

Shame but it's a big ask unfortunately.

[Kwakkelde Kwak]

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Sassy Romano wrote:

[...] but as others have said, to get that to render in the likes of Marvelous Designer, takes a while for the simulation to complete, during that time it is calculating all the positions of the various vertices, how they interact, what collides with what and

then it's saved ready for playback

at normal speed.

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The PhysX APEX (and similair software) is capable of real time rendering the cloth simulation, you do need some up-to-the-task hardware of course.

I have no idea how hard it is to make an on/off switch for people with lower end computers, but as long as rigging itself isn't near complete in SL, I'd rather have LL focusing on other things.

[Jennifer Boyle]

Thank you all for your helpful answers.

After looking at the videos, I really want APEX!