texture blotch BlendFactor surfaceBlotch produces an almost cloud-like pattern; BlendFactor ranges from -1 to 1, with 0 providing an approximately even mix of the object surface and the "blotch surface".
Use this surface where you want to have an object which is mix of colours; perhaps to show spilt water? It can also be used to good advantage when the alternate surfaces are quite similar in colour - to produce a subtle alteration of surface colour (or reflectivity....).
In the example below, the amount of the blotch surface (white) decreases from a "high" on the left of -0.75 (that is: 12.5% default 87.5% blotch) to a "low" on the right of 0.50 (that is: 75% default 25% blotch).
Figure 7-1
/*
blotch.ray
Blotch Example
Stephen Peter 12 Feb 93
*/
eyep 0 -1 75
lookp 0 0 0
light 1 point 40 -40 40
screen 300 300
background .9 .9 .9
surface blue
ambient 0.2 0.2 0.5
diffuse 0.1 0.1 0.3
specular 0.3 0.3 0.6
specpow 10
reflect 0.4
surface white
ambient 0.3 0.3 0.3
diffuse 0.5 0.5 0.5
specular 0.5 0.5 0.5
specpow 10
reflect 0.4
box blue -29 1 -1 -11 29 1
texture blotch -0.75 white
box blue -9 1 -1 9 29 1
texture blotch -0.50 white
box blue 11 1 -1 29 29 1
texture blotch -0.25 white
box blue -29 -29 -1 -11 -1 1
texture blotch 0.00 white
box blue -9 -29 -1 9 -1 1
texture blotch 0.25 white
box blue 11 -29 -1 29 -1 1
texture blotch 0.50 white
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THE END - Notes on Rayshade - 7 - Textures - Blotch