Section 4.8.2.4
Using Transparent Pigments and Layered Textures

Pigments are described by numerical values that give the rgb value of the color to be used (like color rgb <1, 0, 0> giving us a red color). But this syntax will give us more than just the rgb values. We can specify filtering transparency by changing it as follows: color rgbf<1, 0, 0, 1>. The f stands for filter, POV-Ray's word for filtered transparency. A value of one means that the color is completely transparent, but still filters the light according to what the pigment is. In this case, the color will be a transparent red, like red cellophane.

There is another kind of transparency in POV-Ray. It is called transmittance or non-filtering transparency (the keyword is transmit). It is different from filter in that it does not filter the light according to the pigment color. It instead allows all the light to pass through unchanged. It can be specified like this: rgbt <1, 0, 0, 1>.

Let's use some transparent pigments to create another kind of texture, the layered texture. Returning to our previous example, declare the following texture.

#declare LandArea = texture { pigment { agate turbulence 1 lambda 1.5 omega .8 octaves 8 color_map { [0.00 color rgb <.5, .25, .15>] [0.33 color rgb <.1, .5, .4>] [0.86 color rgb <.6, .3, .1>] [1.00 color rgb <.5, .25, .15>] } } } }

This texture will be the land area. Now let's make the oceans by declaring the following.

#declare OceanArea = texture { pigment { bozo turbulence .5 lambda 2 color_map { [0.00, 0.33 color rgb <0, 0, 1> color rgb <0, 0, 1>] [0.33, 0.66 color rgbf <1, 1, 1, 1> color rgbf <1, 1, 1, 1>] [0.66, 1.00 color rgb <0, 0, 1> color rgb <0, 0, 1>] } } } }

Note how the ocean is the opaque blue area and the land is the clear area which will allow the underlying texture to show through.

Now, let's declare one more texture to simulate an atmosphere with swirling clouds.

#declare CloudArea = texture { pigment { agate turbulence 1 lambda 2 frequency 2 color_map { [0.0 color rgbf <1, 1, 1, 1>] [0.5 color rgbf <1, 1, 1, .35>] [1.0 color rgbf <1, 1, 1, 1>] } } }

Now apply all of these to our sphere.

sphere { <0,0,0>, 1 texture { LandArea } texture { OceanArea } texture { CloudArea } }

We render this and have a pretty good rendition of a little planetoid. But it could be better. We don't particularly like the appearance of the clouds. There is a way they could be done that would be much more realistic.

Section 4.8.2.5
Using Pigment Maps

Pigments may be blended together in the same way as the colors in a color map using the same pattern keywords that we can use for pigments. Let's just give it a try.

We add the following declarations, making sure they appear before the other declarations in the file.

#declare Clouds1 = pigment { bozo turbulence 1 color_map { [0.0 color White filter 1] [0.5 color White] [1.0 color White filter 1] } } #declare Clouds2 = pigment { agate turbulence 1 color_map { [0.0 color White filter 1] [0.5 color White] [1.0 color White filter 1] } } #declare Clouds3 = pigment { marble turbulence 1 color_map { [0.0 color White filter 1] [0.5 color White] [1.0 color White filter 1] } } #declare Clouds4 = pigment { granite turbulence 1 color_map { [0.0 color White filter 1] [0.5 color White] [1.0 color White filter 1] } }

Now we use these declared pigments in our cloud layer on our planetoid. We replace the declared cloud layer with.

#declare CloudArea = texture { pigment { gradient y pigment_map { [0.00 Clouds1] [0.25 Clouds2] [0.50 Clouds3] [0.75 Clouds4] [1.00 Clouds1] } } }

We render this and see a remarkable pattern that looks very much like weather patterns on the planet earth. They are separated into bands, simulating the different weather types found at different latitudes.

Section 4.8.3
Normals

Objects in POV-Ray have very smooth surfaces. This is not very realistic so there are several ways to disturb the smoothness of an object by perturbing the surface normal. The surface normal is the vector that is perpendicular to the angle of the surface. By changing this normal the surface can be made to appear bumpy, wrinkled or any of the many patterns available. Let's try a couple of them.

Section 4.8.3.1
Using Basic Normal Modifiers

We comment out the planetoid sphere for now and, at the bottom of the file, create a new sphere with a simple, single color texture.

sphere { <0,0,0>, 1 pigment { Gray75 } normal { bumps 1 scale .2 } }

Here we have added a normal block in addition to the pigment block (note that these do not have to be included in a texture block unless they need to be transformed together or need to be part of a layered texture). We render this to see what it looks like. Now, one at a time, we substitute for the keyword bumps the following keywords: dents, wrinkles, ripples and waves (we can also use any of the patterns listed in "Patterns"). We render each to see what they look like. We play around with the float value that follows the keyword. We also experiment with the scale value.

For added interest, we change the plane texture to a single color with a normal as follows.

plane { y, -1.5 pigment { color rgb <.65, .45, .35> } normal { dents .75 scale .25 } }

Section 4.8.3.2
Blending Normals

Normals can be layered similar to pigments but the results can be unexpected. Let's try that now by editing the sphere as follows.

sphere { <0,0,0>, 1 pigment { Gray75 } normal { radial frequency 10 } normal { gradient y scale .2 } }

As we can see, the resulting pattern is neither a radial nor a gradient. It is instead the result of first calculating a radial pattern and then calculating a gradient pattern. The results are simply additive. This can be difficult to control so POV-Ray gives the user other ways to blend normals.

One way is to use normal maps. A normal map works the same way as the pigment map we used earlier. Let's change our sphere texture as follows.

sphere { <0,0,0>, 1 pigment { Gray75 } normal { gradient y frequency 3 turbulence .5 normal_map { [0.00 granite] [0.25 spotted turbulence .35] [0.50 marble turbulence .5] [0.75 bozo turbulence .25] [1.00 granite] } } }

Rendering this we see that the sphere now has a very irregular bumpy surface. The gradient pattern type separates the normals into bands but they are turbulated, giving the surface a chaotic appearance. But this give us an idea.

Suppose we use the same pattern for a normal map that we used to create the oceans on our planetoid and applied it to the land areas. Does it follow that if we use the same pattern and modifiers on a sphere the same size that the shape of the pattern would be the same? Wouldn't that make the land areas bumpy while leaving the oceans smooth? Let's try it. First, let's render the two spheres side-by-side so we can see if the pattern is indeed the same. We un-comment the planetoid sphere and make the following changes.

sphere { <0,0,0>, 1 texture { LandArea } texture { OceanArea } //texture { CloudArea } // <-comment this out translate -x // <- add this transformation }

Now we change the gray sphere as follows.

sphere { <0,0,0>, 1 pigment { Gray75 } normal { bozo turbulence .5 lambda 2 normal_map { [0.4 dents .15 scale .01] [0.6 agate turbulence 1] [1.0 dents .15 scale .01] } } translate x // <- add this transformation }

We render this to see if the pattern is the same. We see that indeed it is. So let's comment out the gray sphere and add the normal block it contains to the land area texture of our planetoid. We remove the transformations so that the planetoid is centered in the scene again.

#declare LandArea = texture { pigment { agate turbulence 1 lambda 1.5 omega .8 octaves 8 color_map { [0.00 color rgb <.5, .25, .15>] [0.33 color rgb <.1, .5, .4>] [0.86 color rgb <.6, .3, .1>] [1.00 color rgb <.5, .25, .15>] } } normal { bozo turbulence .5 lambda 2 normal_map { [0.4 dents .15 scale .01] [0.6 agate turbulence 1] [1.0 dents .15 scale .01] } } }

Looking at the resulting image we see that indeed our idea works! The land areas are bumpy while the oceans are smooth. We add the cloud layer back in and our planetoid is complete.

There is much more that we did not cover here due to space constraints. On our own, we should take the time to explore slope maps, average and bump maps.

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