13-texture - Texture Mapping NOTES Assignment # 2 due Feb....

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1 Texture Mapping Texture Mapping Lecture 13 CPSC 478/578 Spring 2005 NOTES Assignment # 2 ± due Feb. 28 11:59pm TA OFFICE HOURS THIS WEEK MONDAY 7-9 pm, Friday 2-5 Quiz # 1 Feb. 23, 2005 ± Problems/short answer ± Covers material up to the end of lecture Feb. 14, 2005 Feb. 14, 2005 ± Allowed 8.5x11 page of notes ± Reading for this week: Text, Chapter 10 + = 1 0 1 0 0 0 ) /( 2 ) /( 0 0 0 0 0 0 0 / c c c f n n f f n f n s s s s z y x z z z z z z z z f aspect f w z y x Revised Perspective Transformation 1 ) /( 2 ) /( ) ( / ) / )( / ( = + + = = = s c far near near far far near near far s c c s c c s w z z z z z z z z z z z fy y z x aspect f x Planes remain planar: 0 ' ' ' ' 0 = + + + = + + + d z c y b x a d cz by ax s s s c c c Filling the Z-buffer ± Because planes remain plane, we can bilinearly interpolate z s at vertices down and across scan lines Z2 Z1 Z3 Z1+ Z3 Z3 Z2
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2 Note Interpolating depths is accurate -- because the depth coordinate was adjusted by a division by zc, for constant ys, change in z is a constant for x Interpolating intensity and normals is an approximation because they were not divided by z c . Why don’t we care: because linear variation of intensity and normals was an approximation in the first place. ' / ) ' ' ' ( c d y b x a zs s s + + = How do we compute shadows in the pipeline? Key insight: o Computing shadows is the same as computing an image from the light source 1.Make a depth map of the points visible to the light Use the same transformations, clippings and projections as from the eye. 2. After computing depths from the real eye point, unproject each point, and project into into the light source depth buffer. http://www-sop.inria.fr/reves/personnel/Marc.Stamminger/psm/ View from light Depth from light Shadows in another view Precomputing phase 1.0 for each light source 1.1 make light point be center of projection 1.2 calculate transformation matrices 1.3 transform object using light point matrices 1.4 render object using zbuffer - lighting is skipped 1.5 save computed zbuffer (depth info) Object rendering phase 2.0 make eye point be center of projection 3.0 recalculate transformation matrices 4.0 transform object using eye point matrices 5.0 render object using zbuffer 5.1 for every pixel visible from eye 5.1.1 transform world point corresponding to pixel to shadow coordinates 5.1.2 for every light source sample saved zbuffer for that light if shadow coordinates < zbuffer value pixel is in shadow http://www.cs.wpi.edu/~matt/courses/cs563/talks/shadow/shadow.html Shadow Buffer Algorithm 3D Rendering Pipeline (for direct illumination) 3D Primitives Modeling Transformation Modeling Transformation Projection Transformation Projection Transformation Clipping Clipping Lighting Lighting Image Viewport Transformation Viewport
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This note was uploaded on 11/21/2009 for the course CPSC 478 taught by Professor Hollyrushmeier during the Spring '05 term at Yale.

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13-texture - Texture Mapping NOTES Assignment # 2 due Feb....

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