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Hierarchical Animation Object Rotations

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Hi. I am totally new to OpenGL and have been bribed into helping a friend with a college project. I know some dx, so he thinks that I should be good at this!! Yeah Right!!! Well here is my problem. The project, as the post-subject states, is on Hierarchical Animation. For this we are going a digger, you know the things on building sites that strangely enough they use to Dig! I have the model defined as a set of different objects. ie, cabin, wheels, upper arm, fore arm and bucket. These objects are made up from a collection of vertices, then quads are specified to use these vertices, resulting in a solid 3d model. My problem is as folows. The idea of Hierarchical Animation, is that if the potition of upper arm is changed, these changes are propagated to its children, fore arm, and bucket are also changed. eg. Lift your upperarm over your head, as a result your fore arm and hand are not over your head, although you did not explicitly modify their position. Then I rotate the upper arm up or down, (ie rotation in the x axis) how do I know where the end of it is, so that I canthen translate to this point, and draw the fore-arm etc..... This has me totally baffeled, cause using glRotatef doesnt give the final position of the points in 3d space. Again, I''m totally new to OpenGL, and there may be a very obivious way around this, but I am at a loss so please help. Thanks Ciaran "Only two things are infinite, the universe and human stupidity, and I''m not sure about the former." --Albert Einstein

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Guest Anonymous Poster
Try this...

http://www.student.math.uwaterloo.ca/~cs488/lectures.pdf

look at the section on Hierarchical Models and Transformations.

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