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greg |
1.1 |
{ |
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Adobe texture. |
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Applies to any large, flat surface. |
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A1 - overall magnitude |
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} |
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{ Basic texture is scaled gradient of 3D Perlin noise function. |
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Additional perturbation is added when in_crack is true. } |
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dx = A1 * noise3a(Px, Py, Pz) + if(in_crack, cdx, 0); |
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dy = A1 * noise3b(Px, Py, Pz) + if(in_crack, cdy, 0); |
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dz = A1 * noise3c(Px, Py, Pz) + if(in_crack, cdz, 0); |
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{ First, compute crack coordinate system, which is at 3 times original |
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bump scale and has additional fractal noise through in for irregularity |
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over an even larger scale. } |
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fn3 = fnoise3(Px, Py, Pz); |
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cu = Px/3 + fn3/30; |
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cv = Py/3 + fn3/30; |
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cw = Pz/3 + fn3/30; |
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{ Test in_crack returns true (positive) when sum of [-1,1] Perlin noise in |
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crack coordinate system is about -.4 times the fractal noise function at |
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the same point. } |
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in_crack = inside(-.02, noise3(cu, cv, cw) + .4*fnoise3(cu, cv, cw), .02); |
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{ Final crack perturbation is 5 times as large as normal gradient at that |
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point in Perlin function, meaning it will yank the surface normal one way |
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or the other along that wiggly line where in_crack is true, yielding an |
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apparent discontinuity in the surface. } |
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cdx = 5*A1*noise3a(cu, cv, cw); |
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cdy = 5*A1*noise3b(cu, cv, cw); |
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cdz = 5*A1*noise3c(cu, cv, cw); |
