### Section 4.8.5.6.7Using Turbulence

As noted in one of the above sections turbulence will have no effect if the constant density function is used (keyword constant). It doesn't matter how much or where we move a point if the density is constant and thus does not depend on the location of the point. We'll get the same density value for all location.

Whenever we add turbulence to a halo we must not use the constant density function.

### Section 4.9Working With Special Textures

Many of the pigment patterns we have seen elsewhere in POV-Ray make use of a color_map statement to blend different colors together. Depending on how we list the entries of the color map, we can fade gradually from one color to the next, or have it abruptly make the transition from one to the next. In fact, the color map is a powerful tool for customizing the various pigment patterns, which requires a bit of practice to learn to use it correctly. And all that's fine, when it's just individual colors we want to use. But what if we could blend entire pigment patterns, normal patterns, or whole other textures? Starting with POV-Ray 3, we can!

In order to experiment with some of the exciting new texturing options, let us set up a basic scene file, into which we will be plugging the example textures to experiment with later. So to begin, we set up the following basic include files, a camera and a light source.

#include "colors.inc" #include "textures.inc" camera { orthographic up <0, 5, 0> right <5, 0, 0> location <0, 0, -25> look_at <0, 0, 0> } light_source { <100, 100, -100> color White }

### Section 4.9.1Working With Pigment Maps

Starting with something simple, let's look at the pigment map. We must not confuse this with a color map, as color maps can only take individual colors as entries in the map, while pigment maps can use entire other pigment patterns. To get a feel for these, let's begin by setting up a basic plane with a simple pigment map. Now, in the following example, we are going to declare each of the pigments we are going to use before we actually use them. This isn't strictly necessary (we could put an entire pigment description in each entry of the map) but it just makes the whole thing more readable.

// simple Black on White checkboard... it's a classic #declare Pigment1 = pigment { checker color Black color White scale .1 } // kind of a "psychedelic rings" effect #declare Pigment2 = pigment { wood color_map { [ 0.0 Red ] [ 0.3 Yellow ] [ 0.6 Green ] [ 1.0 Blue ] } } plane { -z, 0 pigment { gradient x pigment_map { [ 0.0 Pigment1 ] [ 0.5 Pigment2 ] [ 1.0 Pigment1 ] } } }

Okay, what we have done here is very simple, and probably quite recognizable if we have been working with color maps all along anyway. All we have done is substituted a pigment map where a color map would normally go, and as the entries in our map, we have referenced our declared pigments. When we render this example, we see a pattern which fades back and forth between the classic checkerboard, and those colorful rings. Because we fade from Pigment1 to Pigment2 and then back again, we see a clear blending of the two patterns at the transition points. We could just as easily get a sudden transition by amending the map to read.

pigment_map { [ 0.0 Pigment1 ] [ 0.5 Pigment1 ] [ 0.5 Pigment2 ] [ 1.0 Pigment2 ] }

Blending individual pigment patterns is just the beginning.

### Section 4.9.2Working With Normal Maps

For our next example, we replace the plane in the scene with this one.

plane { -z, 0 pigment { White } normal { gradient x normal_map { [ 0.0 bumps 1 scale .1] [ 1.0 ripples 1 scale .1] } } }

First of all, we have chosen a solid white color to show off all bumping to best effect. Secondly, we notice that our map blends smoothly from all bumps at 0.0 to all ripples at 1.0, but because this is a default gradient, it falls off abruptly back to bumps at the beginning of the next cycle. We Render this and see just enough sharp transitions to clearly see where one normal gives over to another, yet also an example of how two normal patterns look while they are smoothly blending into one another.

The syntax is the same as we would expect. We just changed the type of map, moved it into the normal block and supplied appropriate bump types. It is important to remember that as of POV-Ray 3, all patterns that work with pigments work as normals as well (and vice versa, of course) so we could just as easily have blended from wood to granite, or any other pattern we like. We experiment a bit and get a feel for what the different patterns look like.

After seeing how interesting the various normals look blended, we might like to see them completely blended all the way through rather than this business of fading from one to the next. Well, that is possible too, but we would be getting ahead of ourselves. That is called the average function, and we will return to it a little bit further down the page.

### Section 4.9.3Working With Texture Maps

We know how to blend colors, pigment patterns, and normals, and we are probably thinking what about finishes? What about whole textures? Both of these can be kind of covered under one topic. While there is no finish map per se, there are texture maps, and we can easily adapt these to serve as finish maps, simply by putting the same pigment and/or normal in each of the texture entries of the map. Here is an example. We eliminate the declared pigments we used before and the previous plane, and add the following.

#declare Texture1 = texture { pigment { Grey } finish { reflection 1 } } #declare Texture2 = texture { pigment { Grey } finish { reflection 0 } } cylinder { <-2, 5, -2>, <-2, -5, -2>, 1 pigment { Blue } } plane { -z, 0 rotate y * 30 texture { gradient y texture_map { [ 0.0 Texture1 ] [ 0.4 Texture1 ] [ 0.6 Texture2 ] [ 1.0 Texture2 ] } scale 2 } }

Now, what have we done here? The background plane alternates vertically between two textures, identical except for their finishes. When we render this, the cylinder has a reflection part of the way down the plane, and then stops reflecting, then begins and then stops again, in a gradient pattern down the surface of the plane. With a little adaptation, this could be used with any pattern, and in any number of creative ways, whether we just wanted to give various parts of an object different finishes, as we are doing here, or whole different textures altogether.

One might ask: if there is a texture map, why do we need pigment and normal maps? Fair question. The answer: speed of calculation. If we use a texture map, for every in-between point, POV-Ray must make multiple calculations for each texture element, and then run a weighted average to produce the correct value for that point. Using just a pigment map (or just a normal map) decreases the overall number of calculations, and our texture renders a bit faster in the bargain. As a rule of thumb: we use pigment or normal maps where we can and only fall back on texture maps if we need the extra flexibility.

### Section 4.9.4Working With List Textures

If we have followed the corresponding tutorials on simple pigments, we know that there are three patterns called color list patterns, because rather than using a color map, these simple but useful patterns take a list of colors immediately following the pattern keyword. We're talking about checker, hexagon, and, new to POV-Ray 3, the brick pattern.

Naturally they also work with whole pigments, normals, and entire textures, just as the other patterns do above. The only difference is that we list entries in the pattern (as we would do with individual colors) rather than using a map of entries. Here is an example. We strike the plane and any declared pigments we had left over in our last example, and add the following to our basic file.

#declare Pigment1 = pigment { hexagon color Yellow color Green color Grey scale .1 } #declare Pigment2 = pigment { checker color Red color Blue scale .1 } #declare Pigment3 = pigment { brick color White color Black rotate -90*x scale .1 } box { -5, 5 pigment { hexagon pigment {Pigment1} pigment {Pigment2} pigment {Pigment3} rotate 90*x } }

We begin by declaring an example of each of the color list patterns as individual pigments. Then we use the hexagon pattern as a pigment list pattern, simply feeding it a list of pigments rather than colors as we did above. There are two rotate statements throughout this example, because bricks are aligned along the z-direction, while hexagons align along the y-direction, and we wanted everything to face toward the camera we originally declared out in the -z-direction so we can really see the patterns within patterns effect here.

Of course color list patterns used to be only for pigments, but as of POV-Ray 3, everything that worked for pigments can now also be adapted for normals or entire textures. A couple of quick examples might look like

normal { brick normal { granite .1 } normal { bumps 1 scale .1 } }

or...

texture { checker texture { Gold_Metal } texture { Silver_Metal } }
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