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Skeletal Animation

Started by Zimans Dec 30, 2000 at 2:33 PM 5 replies 1.3k views

Original Post

Dec 30, 2000 at 2:33 PM

How many games currently on the market or soon to be on the market use a dynamic skeletal animation system. In another words, a skeleton is applied to the model at run-time, instead of pre-calculating all the frames beforehand and loading them. It seems to me that Quake 3 and ALice (Wich is based of teh Q3 engine), two games I''ve played recently, have some sort of simple system as I''ve noticed that while strafing the torso actually turns to face forward while the lower body faces more towards the way you are running... I''ve been thinking about and plan to attempt to construct a simple skeletal animation system of my own to mess around with. It seems to me that this kind of system would lead to more interesting fights etc. My setting in mind is battles like in squaresoft games, except instead of having them just stand there, let them move around and engage the enemies in actual combat. With some sort of skeletal system the battles would be more interesting since the models are not locked to pre-calculated frames, instead they can be addaptive to what is happening... I realize that this could become computationally intensive. But I think the concept is interesting and worth expiriementing woth. Especially if there are only 6 or 7 models on the screen, then it may actually be plausible.. Either way, another question: I''m just looking to see what other people think about this and what points could be brought up about such a system... Thx -Zims

Shannon Barber

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368

Shannon Barber

Dec 30, 2000 at 8:15 PM

It requires a lot more rotation transformations of the sprite''s geometry as you render it. So it impacts scene complexity & frame rate... Instead of one transformation per sprite, its one tranformation per sprite part (~15).

If done throughly its an awesome effect.

MrTors

Dec 30, 2000 at 8:45 PM

I would think skeletal animations would be the best way to go with games that have more depth with the physics. That way the body of the object that you are animating could also be more dynamic to match the physical effects that are acting upon it. Of course it would depend in the complexity of the model how crazy you want to get with it. I don''t know about how most games do it, but I was playing Tekken Tag the other day and I would think they would have to do some skeletal animations there. It looks like any character can be made to move like any other character. I guess the question still is, whether you do the calculations for most animations before or you do it real-time. Either way i guess you''d still be applying a skeletal structure to something. You''d just have to find a way around those bottle necks.

bishop_pass

297

bishop_pass

Dec 31, 2000 at 1:30 AM

Develop for tomorrow''s anticipated CPU speed, because I guarentee that if you don''t, somebody else is.

You make the choice: do what''s being done now and have it be obsolete and unimpressive tomorrow, or get the headstart on the inevitable.

It''s interesting to note how everyone develops target framerates of 60 FPS or so. I''m always thinking, can I do this in 10 FPS? If so, by the time I get a full project together, high end machines should be able to drive it at 60 FPS.

Show me something going at 60 FPS, and I won''t be impressed. What I''ll be seeing is simple models doing simple things like everyone else''s projects. Show me something at 10 FPS, and hopefully I''ll be seeing advanced algorithms doing truly wonderful things. And I know it''ll only be a little while when that will run at a better framerate.

MrTors

Dec 31, 2000 at 3:58 AM

Show me something running at 10 fps on today''s average machine and I''ll tell you cut out more than half your market.

lucid

Dec 31, 2000 at 5:59 AM

MrTors.. hes talking about the future.. thus only 5% or so would be cut out... his point is great

Zimans

Author

Zimans

Dec 31, 2000 at 4:34 PM

I did some more thinking and reading up about various things about skeletal animation and came up with a few more quandries.

Quake3 was supposed to have some sort of skeletal animation, but instead I guess they dropped it for a simpler version. From what I''ve read they use three seperate models, and then put them together to create the final model..

What I had in mind was taking a single complete model, and grouping all the verts into groups, or segemnts, that represented all the parts of the skeleton. (Hand, Lower Arm, Upper Arm, torso, etc..) But the problem I''ve come accross is keeping the triangle lists correct. Since each appendage would be transformed first, then added collectively together to the torso, the vertex order would not be presereved. The only solution I can come up with is giving each vertex a specific index that will stay with it through the transformations, and then once transformations are complete, build the triangle list by traversing the final vertex buffer looking for the correct vertex. I guess it wouldn''t be that much extra processing but it is a pass through the list I would like to avoid. The other method would be to do the seperate pieces, But I like the idea of making them all one because then as one segment moves it will cause the texture to respond...

either way.. Any thoughts?

-Zims

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