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Texture Mapping
Fall 2012
(Slides mostly based on those of Voicu Popescu) Daniel G. Aliaga
Department of Computer Science Purdue University
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Texture mapping
• Model surface-detail with images
– wrap object with photograph(s)
– graphics object itself is a simpler model but “looks” more complex
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Texture mapping
• Model surface-detail with images
– wrap object with photograph(s)
– graphics object itself is a simpler model but “looks” more complex
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Texture mapping
• Generic image to represent material
– e.g., tile pattern
bark
veneer
bricks
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Tiling
• Repeat pattern
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Tiling
• Repeat pattern
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Tiling
• Repeat pattern
• How can we improve?
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Tiling
• Repeat pattern
– reduce seems by mirroring
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Tiling
• Repeat pattern
– reduce seems by mirroring
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Tiling
• Repeat pattern
– reduce seems by mirroring
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Tiling
• Repeat pattern
– reduce seems by mirroring
– How we can further improve?
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Tiling
• Repeat pattern
– reduce seems by mirroring
– reduce seems by choosing tile that covers one period of repeated texture
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Tiling
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Texture mapping limitations do exist…
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Bricks are similar not identical
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Solution?
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Solution: Texture synthesis…
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Texture coordinates
• Mechanism for attaching the texture map to the surface modeled
– a pair of floats (s, t) for each triangle vertex
– corners of the image are (0, 0), (0, 1), (1, 1), and (1, 0)
– tiling indicated with tex. coords. > 1
– texels – color samples in texture maps
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x
y
z
O
P2(0, 0)
P1(1, 0)
P4(1, 1)
P3(0, 1)
Texture coordinates
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Texture mapping
C
c
a
b
P1’
P2(0, 0)
P2’
P3’
P1(1, 0)
P4(1, 1)
P3(0, 1)
x
y
z
O
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Texels: texture elements
P1’(u1, v1, s1, t1)
P2’(u2, v2, s2, t2) P3’(u3, v3, s3, t3)
P’(u, v, s, t)
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Texture mapping
C
c
a
b
P1’
P2(s2, t2)
P2’
P3’
P1(s1, t1)
P3(s3, t3)
P (s, t)
P’
x
y
z
O
Problem: how to
compute the texture
coordinates for an
interior pixel?
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Texture mapping
C
c
a
b
P1’
P2(s2, t2)
P2’
P3’
P1(s1, t1)
P3(s3, t3)
P (s, t)
P’
x
y
z
O
Solution: interpolate
vertex texture coordinates
Parameter Interpolation
• Texture coordinates, colors, normals, etc.
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Level of detail problem
aliasing anti-aliased
If curious, you can read more on this subject!
