CSL 859: Advanced Computer Graphics

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CSL 859 Advanced Computer Graphics

• Dept of Computer Sc. Engg.
• IIT Delhi

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Graphics Pipeline

• Transform vertices
• Light vertices
• Clip to Window extremes
• Setup edges
• Rasterize
• Fill and interpolate colors, depth
• Test against Z-buffer
• One entry per pixel closest so far
• Update Color and Z buffers

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Light Vertices
Color
Light Direction
normal
Point Directional Or Both
View Direction
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Lighting in which space?

• Projective?
• Distances get distorted
• Clip coordinates
• Normalized device coordinates
• Screen?
• World
• Camera

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Homogeneous Space Clipping

• Clip coordinates projective coordinates
• -1 lt x/z lt 1 (after perspective divide)
• -1 lt x/w lt 1 (clip)
• -w lt x lt w
• -w lt y lt w
• 0 lt z lt w

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Rasterize
x0,y0,z0
y mx c x 1/m(yc) ayb
x2,y2,z2
x1 aya b x a
x1, y1,z1
zp1 zp k
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Perspective Distortion
z2
z1
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Perspective Distortion
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Perspective Correction

• Linear interpolation
• p(t) p1 (p2 p1) t, 0 lt t lt 1
• Screen space interpolation
• ys y1s t (y2s y1s)
• y/z y1/z1 t (y2/z2 y1/z1)
• But also
• y y1 u (y2 y1)
• z z1 u (z2 z1)

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Perspective Correction
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Perspective Correction
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Perspective Correct Z
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Perspective Corrected