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# 3d rendering

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I am not entirely new to 3d api''s, I have done a little with opengl and directx but would like to understand whats going on within the api''s. I was hoping someone could point me to a good tutorial about what exactly happens to a point as its transformed from its 3d points to its 2d points. Thank you Ian

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There''s a nice little page on Kenny Hoff''s site...

http://www.cs.unc.edu/~hoff/techrep/index.html

If you look at the link "A view of the typical vertex transformation pipeline (word .doc)" you should get a better overall view of what happens to a point. After that it''s all down to the matrices. Knowing how they work is very valuable, so it''s a good idea to read those sections in the D3D/OGL docs to understand how they''re constructed and how they work together.

Helpful links:
How To Ask Questions The Smart Way | Google can help with your question | Search MSDN for help with standard C or Windows functions

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Thanks for the reply but I was actually more interested in how the transformations are done.

I think the object -> world is easy, just moving the object from being at 0,0,0 to its location in the world.

But the camera transformation is something which I could read a more detailed explanation of. Or at least the calculations. And then an explanation of how to take these finals points and render them in 2d.

Thanks
Ian

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Go here and check out the thing called 3dgpl2. It''s essentially a book teaching you how to write software 3d engines. You may find it helpful

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quote:

Thanks for the reply but I was actually more interested in how the transformations are done.

Every transformation is nothing but a matrix multiply.

quote:

I think the object -> world is easy, just moving the object from being at 0,0,0 to its location in the world.

The pipeline doesn''t move anything. The world->object transformation step is just a matrix multiply: the vector gets multiplied by the object''s local transformation matrix. Same thing for the world->camera step: again a matrix multiply, this time with the view matrix. Perspective transformation is, you guessed it, another matrix multiply, with a special projection matrix. The last step to get the 2D coordinates is the persepctive division. That''s simply 3 divides (x/w, y/w and z/w).

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Yup, I should have explained further, but Yann L hit the nail right on the head. If you look at the word doc on Kenny Hoff''s site, each of the stages between different coordinate spaces is just a vector-by-matrix multiply, finishing off with a divide by w.

Helpful links:
How To Ask Questions The Smart Way | Google can help with your question | Search MSDN for help with standard C or Windows functions

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