Blotch

        texture blotch BlendFactor surface
Blotch 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