Class4

# Class4 - Class 4. Spaces needed to coordinate modeling,...

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Class 4. Spaces needed to coordinate modeling, animation, viewing, and rendering Ulrich Neumann CS580 (Computer Graphics Rendering)

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Spaces : model, world, image (camera), perspective (NDC), screen screen is pixel coords like FB in HW1 (Right-handed coords) perspective is NDC (x, y = [-1,1], z = [0,1]) (LHC) image has center of projection plane at (0,0,0), looking along +z (LHC) world has all some origin/axis as reference for object locations (LHC) model has coord frame(s) of its own (LHC) All are left-handed except for screen, which is right-handed x y z-in x y z-in
Transforms : screen X sp perspective (NDC) X pi image X iw world X wm model Xforms are between spaces - Renderer maintains the complete transformation X sm Application/animation controls each transform for different purposes X wm object positions (per frame or per instance) X iw camera motion/external parameters (per frame) X pi camera FOV (focal length, zoom) internal parameters (per frame) X sp screen or frame-buffer mapping (per session)

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Managing Xforms Use one of more stack structures that allow push/pop operations. Push in sequence from screen to model. Pop as many as needed in reverse order to allow push of modified matrix. Complete pushes before rendering next frame. Full stack must transform models to screen Xsm Let stack accumulate transforms, rather than just storing them Push A Top of stack = (A) Push B Top of stack = (AB) Push C Top of stack = (ABC) Pop Top of stack = (AB) Push D Top of stack = (ABD)
How to move camera Change X iw to produces a camera change Build new X iw (show how in later slide) Pop to remove X wm from full X sm stack – leaves X sw on stack Pop to remove X iw from X sm

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## This note was uploaded on 04/22/2010 for the course CS 580 at USC.

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Class4 - Class 4. Spaces needed to coordinate modeling,...

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