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Modern ways of handling physical interaction between two models

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Good day everyone, I'm a very fresh member of these forums so I hope I have picked the right board for this subject. I'm interested in the possible ways (and mostly future possibities) of handling physical interaction between two bodies in a 3D game environment. For example: the player grabbing an enemy by the arm. The most common way I see this being implemented as I see it is this: - player initiates a move - both the player and the enemy play preset animations - both are then slightly displaced in the game world, so that the animations fit correctly, usually with the unwanted visual effect that the models are sliding over the floor My first, shorter question is: Is there a popular name for this? My second question about this is: What are the alternatives? Since the implementation I described above seems rather static to me, I think its only natural for the industry to have already tried out different ways of making it more dynamic (making it less dependant on preset animations maybe). Maybe I'm far behind the times, in which case I apologize. Anyway, I'm very curious about your thoughts and knowledge about this subject. If you can recommend some books about this subject, I'd be grateful as well. Thanks in advance! Nisshoku

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1. I don't know if there's a popular name for what you describe. [SMILE]

2. I'm not sure what you're looking for an alternative to, exactly.

If it's just the "sliding," that can be eliminated by blending in a walking animation along with the "grab" animation.

An alternative to "static" animations might be to blend several animations to, at least, provide some variety, but still resulting in the proper positioning of the models.

If it's an alternative to scripted or preset interactions, I haven't done that myself. It would seem to require creating animation frames "on the fly," which I think you're getting at in the latter part of your post. I don't think that would necessarily be computationally expensive, once you figure out the general theory of moving a bone frame to a particular point. That may be the challenge.

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Thank you for the replies.

I've seen some videos from that Euphoria project already, its really awesome yes! :) I'm CERTAINLY interested in how that works, can anyone perhaps name a few sources/books about this (kind of) technology?

And sorry that my second question was a bit vague. I wanted to know if perhaps some games already use different approaches to interaction between 2 models, instead of what I described in the first post.


My main mission is to learn more about the subject, not yet to put it to practical use.

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Popular techniques for what you're describing are called Inverse Kinematics and animation syncronization.

For IK you start with a math equation that given a target hand location will generate the necessary joint angles to reach it. Then using the opponent's arm as a target, you'll continually compute your arm angles to keep your hand positioned over his. IK can also be solved iteratively. One way to do it iteratively would be to model the arms physically with rigid bodies and joints. The hand would then be constrained to the arm with a force and the physics engine would solve the arm chain how ever necessary to satisfy the force.

Animation syncronization involves an artist. The artist would create two animations that when played at the same time, speed, and at a particular location will appear to be connected to each other. It is then up to the programmer to insure that these 3 things happen correctly. Since the animation is usually triggered at time where all 3 of these things are NOT satisfied, the programmer will blend them over time until they are satisfied, accepting some visual artifacts.

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