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vicviper

max export: Physique or Skin?

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Hi, I''m building a max export plugin, I already have programmed the physique export interface and it seems to be working well... But I have recently had a discussion with an artist that says that the Skin modifier is much better than physique for animation purposes... So, why everybody chooses Physique over Skin for animating game characters? it is a technical problem (trouble exporting Skin data?) or an artistic issue (physique being more advanced and difficult to learn?) Also, I don''t understand why Physique is needed if Max already has the Skin modifier I don''t want to start a flame war, just interested in knowing the advantages and issues of both modifiers, from both programing and artistic points of view.

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The skin modifier uses a bone-based skinning system similar to what most game engines use. Physique uses a bizarre animation system that involves bones, vertices, and "links". Links are similar to bones except that they flex, as if they''re made of rubber. The vertices aren''t attached to the bones, they''re attached to the links. When the link flexes, so do all the vertices attached to it. The problem is, most game engines don''t implement anything like that. So what it comes down to: an model exported from skin is likely to look the same in your engine, a model exported by physique is likely to look different in the engine than in MAX. In particular, models exported from physique tend to have crinkles and protrusions around the joints.

So at one point, I tried to get our artists to use "skin", but they resisted me forcefully. The problem is, the skin user interface is really bad. Frequently, clicking on bones doesn''t even register. The type-in interface for weights is painful. You can''t visualize the envelopes. Simply put, the artists didn''t want to use this piece of junk.

So here''s the workaround: select the physique modifier, select sub-object links, and dink around with the bend tension and bias, and maybe the continuity check-box. I can''t remember the actual settings, but if you get them right, you can get the links to stay right in the center of the bones. Once you''ve done this, you''ve effectively got a bone-based animation system. In this way, you get the advantage of physique''s better user interface, but with accurate playback as well.

Oh, one more thing - the skin export API is so similar to the physique export API, I figure if you''ve already written one, you might as well write the other. It''s only a dozen more lines of code. That way, your exporter can support both.

- Nekhmet

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Thanks a lot, your info has been very helpful

We have Max 5 licenses, and some artists have told me that Skin modifier now have envelopes and good tools for generating weights, even a weight painter tool, so they actually preffer to work with Skin modifier over Physique modifier.

It's weird, but, whenever I check forums, FAQs, etc, everybody talked about "skin for rendering" and "physique for games"...

anyway, just began doing the code for supporting Skin modifier

Thanks again

[edited by - vicviper on September 26, 2003 4:04:03 AM]

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Skin used to be kind of shoddy, but it''s improved a lot over the last few years. It still has some quirks here and there, but all in all it''s easier to use, does pretty much everything you need, and is included in the base package...so it works on any copy of Max, not just ones that have Character Studio installed.

As for why there are two weighting systems in Max, I think it comes down to politics. Character Studio, of which Physique is a part of, is distributed by Discreet, but it''s developed by 3rd party developers. So, for Max 3 they decided to put a weighting system in the base package but they probably couldn''t, or didn''t want to, break up the Character Studio add-on by taking Physique out of it and putting it into the base package. Instead, they made Skin, which was originally billed as a kind of Physique light. Needless to say, over the years people asked for improvements for Skin and now it''s pretty good.

Now you''re in the know

-John

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