1. Volumetric Texture Mapping
Texture Mappings
9/11/2018
Volumetric Texture Mapping
Solid Texturing of Complex Surfaces/Darwyn R. Peachey (SIGRAPH’85)
An Image Synthesize/Ken Perlin (SIGRAPH’85)
Computer Graphics
Gil Zigelman

2. Principles
The volumetric texture mapping involves a 3D function r which gives for each point P the color of P:
r = r(x,y,z)
In a rendering process, for each point P(x0,y0,z0) of the object’s surface to display, one computs the color at this point: r(x,y,z)
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3. Principles - cont.
This color is the color of the object before any illumination effect.
example:
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4. Transformations
When an object with a volumetric texture mapping is transformed (translation, rotation or scaling), the volumetric texture mapping function must also be transformed.
The function r must follow the transformations of the object.
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5. Example
Translation of the object without any change in the volumetric texture mapping function:
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6. Effects
Bombing
A fixed number of bubbles is generated. Each bubble has a radius, and a location in the space which are chosen randomly.
For each point of the object’s surface which is displayed, one verifies if the point belongs to one of the bubbles.
If the point belongs to one of the bubbles, the point is displayed in the bubble’s color
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7. Effects - Cont.
Otherwise, the point is displayed in the object’s color.
Example:
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8. Bombing - Example
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9. Effects - Cont.
Wood
The function r is an orthogonal projection of a set of concentric circles.
Eample:
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10. Wood - Examples
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11. Wood - Examples
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12. Effects - Cont. Boring Marble The function is a sinus: (sin(x),y,z)
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13. Function Noise
The function Noise returns a scalar for all point P(x,y,z).
Such a function is defined as follows:
For each x,y,z in Z (x, y and z are integers): H(x,y,z) = d (d is a randomly chosen value)
If (x,y,z) are all integers:
Noise(x,y,z) = H(x,y,z)
Otherwise:
Noise(x,y,z) = interpolation of neighbouring H(x,y,z)
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14. Function Noise - Cont.
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15. Function DNoise
The function Dnoise is the differential of the function Noise:
Dnoise(x,y,z) = (dNoise/dx, dNoise/dy, dNoise/dz)
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16. Function Turbulence function turbulence(p) t=0 scale=1
while (scale>pixelsize) {
t+=abs(Noise(p/scale)*scale)
scale/=2 }
return t
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17. More Effects
Marble
The marble effect is obtained using the function turbulence:
function marble(point)
x=point[1]+turbulence(point)
return marble_color(sin(x))
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18. Marble - Examples
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19. Marble - Examples
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20. More Effects Simple: Bumpy surface: color=white*Noise(point)
normal+=Dnoise(point)
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21. Spotted Donut
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22. Example - Bumpy Donut
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23. Another Example...
color = Colorful(Noise(k*point))
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24. Example - Art Glass
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25. Example - Corona
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