The extremely powerful texturing ability is one thing that really sets POV-Ray apart from other raytracers. So far we have not really tried anything too complex but by now we should be comfortable enough with the program's syntax to try some of the more advanced texture options.

Obviously, we cannot try them all. It would take a tutorial a lot more pages to use every texturing option available in POV-Ray. For this limited tutorial, we will content ourselves to just trying a few of them to give an idea of how textures are created. With a little practice, we will soon be creating beautiful textures of our own.

Note: early versions of POV-Ray made a distinction between pigment and normal patterns, i. e. patterns that could be used inside a normal or pigment statement. Since POV-Ray 3.0 this restriction was removed so that all patterns listed in section "Patterns" can be used as a pigment or normal pattern.

Let's begin texturing our sphere by using a pattern and a color map consisting of three colors. We replace the pigment block with the following.

  pigment {
    gradient x
    color_map {
      [0.00 color Red]
      [0.33 color Blue]
      [0.66 color Yellow]
      [1.00 color Red]
    }
  }

Let's take a look at some pattern modifiers. First, we change the pattern type to bozo. Then we add the following change.

  pigment {
    bozo
    frequency 3            // <- add this line
    color_map {
      [0.00 color Red]
      [0.33 color Blue]
      [0.66 color Yellow]
      [1.00 color Red]
    }
    rotate -45*z
  }

Pigments may be blended together in the same way as the colors in a color map using the same pattern keywords and a pigment_map. 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.

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 }
  }

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 gives 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? Would not 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.

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 is not 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 checkerboard... 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.

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, except for facets) 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.

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.

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 are talking about checker, hexagon, the brick pattern and the object 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 }
  }

In earlier versions of POV-Ray, there was a texture pattern called tiles. By simply using a checker texture pattern (as we just saw above), we can achieve the same thing as tiles used to do, so it is now obsolete. It is still supported by POV-Ray 3 for backwards compatibility with old scene files, but now is a good time to get in the habit of using a checker pattern instead.

With the multitudinous colors, patterns, and options for creating complex textures in POV-Ray, we can easily become deeply engrossed in mixing and tweaking just the right textures to apply to our latest creations. But as we go, sooner or later there is going to come that special texture. That texture that is sort of like wood, only varnished, and with a kind of spotty yellow streaking, and some vertical gray flecks, that looks like someone started painting over it all, and then stopped, leaving part of the wood visible through the paint.

Only... now what? How do we get all that into one texture? No pattern can do that many things. Before we panic and say image map there is at least one more option: layered textures.

With layered textures, we only need to specify a series of textures, one after the other, all associated with the same object. Each texture we list will be applied one on top of the other, from bottom to top in the order they appear.

It is very important to note that we must have some degree of transparency (filter or transmit) in the pigments of our upper textures, or the ones below will get lost underneath. We will not receive a warning or an error - technically it is legal to do this: it just does not make sense. It is like spending hours sketching an elaborate image on a bare wall, then slapping a solid white coat of latex paint over it.

Let's design a very simple object with a layered texture, and look at how it works. We create a file called LAYTEX.POV and add the following lines.

  #include "colors.inc"
  #include "textures.inc"
  camera {
    location <0, 5, -30>
    look_at <0, 0, 0>
  }
  light_source { <-20, 30, -50> color White }
  plane { y, 0 pigment { checker color Green color Yellow  } }
  background { rgb <.7, .7, 1> }
  box {
    <-10, 0, -10>, <10, 10, 10>
    texture {
      Silver_Metal // a metal object ...
      normal {     // ... which has suffered a beating
        dents 2
        scale 1.5
      }
    } // (end of base texture)
    texture { // ... has some flecks of rust ...
      pigment {
        granite
        color_map {
          [0.0 rgb <.2, 0, 0> ]
          [0.2 color Brown ]
          [0.2 rgbt <1, 1, 1, 1> ]
          [1.0 rgbt <1, 1, 1, 1> ]
        }
        frequency 16
      }
    } // (end rust fleck texture)
    texture { // ... and some sooty black marks
      pigment {
        bozo
        color_map {
          [0.0 color Black ]
          [0.2 color rgbt <0, 0, 0, .5> ]
          [0.4 color rgbt <.5, .5, .5, .5> ]
          [0.5 color rgbt <1, 1, 1, 1> ]
          [1.0 color rgbt <1, 1, 1, 1> ]
        }
        scale 3
      }
    } // (end of sooty mark texture)
  } // (end of box declaration)

Whew. This gets complicated, so to make it easier to read, we have included comments showing what we are doing and where various parts of the declaration end (so we do not get lost in all those closing brackets!). To begin, we created a simple box over the classic checkerboard floor, and give the background sky a pale blue color. Now for the fun part...

To begin with we made the box use the Silver_Metal texture as declared in textures.inc (for bonus points, look up textures.inc and see how this standard texture was originally created sometime). To give it the start of its abused state, we added the dents normal pattern, which creates the illusion of some denting in the surface as if our mysterious metal box had been knocked around quite a bit.

The flecks of rust are nothing but a fine grain granite pattern fading from dark red to brown which then abruptly drops to fully transparent for the majority of the color map. True, we could probably come up with a more realistic pattern of rust using pigment maps to cluster rusty spots, but pigment maps are a subject for another tutorial section, so let's skip that just now.

Lastly, we have added a third texture to the pot. The randomly shifting bozo texture gradually fades from blackened centers to semi-transparent medium gray, and then ultimately to fully transparent for the latter half of its color map. This gives us a look of sooty burn marks further marring the surface of the metal box. The final result leaves our mysterious metal box looking truly abused, using multiple texture patterns, one on top of the other, to produce an effect that no single pattern could generate!

In the event we want to reuse a layered texture on several objects in our scene, it is perfectly legal to declare a layered texture. We will not repeat the whole texture from above, but the general format would be something like this:

  #declare Abused_Metal =
    texture { /* insert your base texture here... */ }
    texture { /* and your rust flecks here... */ }
    texture { /* and of course, your sooty burn marks here */ }

POV-Ray has no problem spotting where the declaration ends, because the textures follow one after the other with no objects or directives in between. The layered texture to be declared will be assumed to continue until it finds something other than another texture, so any number of layers can be added in to a declaration in this fashion.

One final word about layered textures: whatever layered texture we create, whether declared or not, we must not leave off the texture wrapper. In conventional single textures a common shorthand is to have just a pigment, or just a pigment and finish, or just a normal, or whatever, and leave them outside of a texture statement. This shorthand does not extend to layered textures. As far as POV-Ray is concerned we can layer entire textures, but not individual pieces of textures. For example

  #declare Bad_Texture =
    texture { /* insert your base texture here... */ }
    pigment { Red filter .5 }
    normal { bumps 1 }

will not work. The pigment and the normal are just floating there without being part of any particular texture. Inside an object, with just a single texture, we can do this sort of thing, but with layered textures, we would just generate an error whether inside the object or in a declaration.

To further explain how layered textures work another example is described in detail. A tablecloth is created to be used in a picnic scene. Since a simple red and white checkered cloth looks entirely too new, too flat, and too much like a tiled floor, layered textures are used to stain the cloth.

We are going to create a scene containing four boxes. The first box has that plain red and white texture we started with in our picnic scene, the second adds a layer meant to realistically fade the cloth, the third adds some wine stains, and the final box adds a few wrinkles (not another layer, but we must note when and where adding changes to the surface normal have an effect in layered textures).

We start by placing a camera, some lights, and the first box. At this stage, the texture is plain tiling, not layered. See file layered1.pov.

  #include "colors.inc"
  camera {
    location <0, 0, -6>
    look_at <0, 0, 0>
  }
  light_source { <-20, 30, -100> color White }
  light_source { <10, 30, -10> color White }
  light_source { <0, 30, 10> color White }
  #declare PLAIN_TEXTURE =
    // red/white check
    texture {
      pigment {
        checker
        color rgb<1.000, 0.000, 0.000>
        color rgb<1.000, 1.000, 1.000>
        scale <0.2500, 0.2500, 0.2500>
      }
    }
  // plain red/white check box
  box {
    <-1, -1, -1>, <1, 1, 1>
    texture {
      PLAIN_TEXTURE
    }
    translate  <-1.5, 1.2, 0>
  }

We render this scene. It is not particularly interesting, is it? That is why we will use some layered textures to make it more interesting.

First, we add a layer of two different, partially transparent grays. We tile them as we had tiled the red and white colors, but we add some turbulence to make the fading more realistic. We add the following box to the previous scene and re-render (see file layered2.pov).

  #declare FADED_TEXTURE =
    // red/white check texture
    texture {
      pigment {
        checker
        color rgb<0.920, 0.000, 0.000>
        color rgb<1.000, 1.000, 1.000>
        scale <0.2500, 0.2500, 0.2500>
      }
    }
    // greys to fade red/white
    texture {
      pigment {
        checker
        color rgbf<0.632, 0.612, 0.688, 0.698>
        color rgbf<0.420, 0.459, 0.520, 0.953>
        turbulence 0.500
        scale <0.2500, 0.2500, 0.2500>
      }
    }
  // faded red/white check box
  box {
    <-1, -1, -1>, <1, 1, 1>
    texture {
      FADED_TEXTURE
    }
    translate  <1.5, 1.2, 0>
  }

Even though it is a subtle difference, the red and white checks no longer look quite so new.

Since there is a bottle of wine in the picnic scene, we thought it might be a nice touch to add a stain or two. While this effect can almost be achieved by placing a flattened blob on the cloth, what we really end up with is a spill effect, not a stain. Thus it is time to add another layer.

Again, we add another box to the scene we already have scripted and re-render (see file layered3.pov).

  #declare STAINED_TEXTURE =
    // red/white check
    texture {
      pigment {
        checker
        color rgb<0.920, 0.000, 0.000>
        color rgb<1.000, 1.000, 1.000>
        scale <0.2500, 0.2500, 0.2500>
      }
    }
    // greys to fade check
    texture {
      pigment {
        checker
        color rgbf<0.634, 0.612, 0.688, 0.698>
        color rgbf<0.421, 0.463, 0.518, 0.953>
        turbulence 0.500
        scale <0.2500, 0.2500, 0.2500>
      }
    }
    // wine stain
    texture {
      pigment {
        spotted
        color_map {
          [ 0.000  color rgb<0.483, 0.165, 0.165> ]
          [ 0.329  color rgbf<1.000, 1.000, 1.000, 1.000> ]
          [ 0.734  color rgbf<1.000, 1.000, 1.000, 1.000> ]
          [ 1.000  color rgb<0.483, 0.165, 0.165> ]
        }
        turbulence 0.500
        frequency 1.500
      }
    }
  // stained box
  box {
    <-1, -1, -1>, <1, 1, 1>
    texture {
      STAINED_TEXTURE
    }
    translate  <-1.5, -1.2, 0>
  }

Now there is a tablecloth texture with personality.

Another touch we want to add to the cloth are some wrinkles as if the cloth had been rumpled. This is not another texture layer, but when working with layered textures, we must keep in mind that changes to the surface normal must be included in the uppermost layer of the texture. Changes to lower layers have no effect on the final product (no matter how transparent the upper layers are).

We add this final box to the script and re-render (see file layered4.pov)

  #declare WRINKLED_TEXTURE =
    // red and white check
    texture {
      pigment {
        checker
        color rgb<0.920, 0.000, 0.000>
        color rgb<1.000, 1.000, 1.000>
        scale <0.2500, 0.2500, 0.2500>
      }
    }
    // greys to "fade" checks
    texture {
      pigment {
        checker
        color rgbf<0.632, 0.612, 0.688, 0.698>
        color rgbf<0.420, 0.459, 0.520, 0.953>
        turbulence 0.500
        scale <0.2500, 0.2500, 0.2500>
      }
    }
    // the wine stains
    texture {
      pigment {
        spotted
        color_map {
          [ 0.000  color rgb<0.483, 0.165, 0.165> ]
          [ 0.329  color rgbf<1.000, 1.000, 1.000, 1.000> ]
          [ 0.734  color rgbf<1.000, 1.000, 1.000, 1.000> ]
          [ 1.000  color rgb<0.483, 0.165, 0.165> ]
        }
        turbulence 0.500
        frequency 1.500
      }
      normal {
        wrinkles 5.0000
      }
    }
  // wrinkled box
  box {
    <-1, -1, -1>, <1, 1, 1>
    texture {
      WRINKLED_TEXTURE
    }
    translate  <1.5, -1.2, 0>
  }

Well, this may not be the tablecloth we want at any picnic we are attending, but if we compare the final box to the first, we see just how much depth, dimension, and personality is possible just by the use of creative texturing.

One final note: the comments concerning the surface normal do not hold true for finishes. If a lower layer contains a specular finish and an upper layer does not, any place where the upper layer is transparent, the specular will show through.

We have some pretty powerful texturing tools at our disposal, but what if we want a more free form arrangement of complex textures? Well, just as image maps do for pigments, and bump maps do for normals, whole textures can be mapped using a material map, should the need arise.

Just as with image maps and bump maps, we need a source image in bitmapped format which will be called by POV-Ray to serve as the map of where the individual textures will go, but this time, we need to specify what texture will be associated with which palette index. To make such an image, we can use a paint program which allows us to select colors by their palette index number (the actual color is irrelevant, since it is only a map to tell POV-Ray what texture will go at that location). Now, if we have the complete package that comes with POV-Ray, we have in our include files an image called povmap.gif which is a bitmapped image that uses only the first four palette indices to create a bordered square with the words "Persistence of Vision" in it. This will do just fine as a sample map for the following example. Using our same include files, the camera and light source, we enter the following object.

  plane {
    -z, 0
    texture {
      material_map {
        gif "povmap.gif"
        interpolate 2
        once
        texture { PinkAlabaster }          // the inner border
        texture { pigment { DMFDarkOak } } // outer border
        texture { Gold_Metal }             // lettering
        texture { Chrome_Metal }           // the window panel
      }
      translate <-0.5, -0.5, 0>
      scale 5
    }
  }

There are a couple limitations to all of the special textures we have seen (from textures, pigment and normal maps through material maps). First, if we have used the default directive to set the default texture for all items in our scene, it will not accept any of the special textures discussed here. This is really quite minor, since we can always declare such a texture and apply it individually to all objects. It does not actually prevent us from doing anything we could not otherwise do.

The other is more limiting, but as we will shortly see, can be worked around quite easily. If we have worked with layered textures, we have already seen how we can pile multiple texture patterns on top of one another (as long as one texture has transparency in it). This very useful technique has a problem incorporating the special textures we have just seen as a layer. But there is an answer!

For example, say we have a layered texture called Speckled_Metal, which produces a silver metallic surface, and then puts tiny specks of rust all over it. Then we decide, for a really rusty look, we want to create patches of concentrated rust, randomly over the surface. The obvious approach is to create a special texture pattern, with transparency to use as the top layer. But of course, as we have seen, we would not be able to use that texture pattern as a layer. We would just generate an error message. The solution is to turn the problem inside out, and make our layered texture part of the texture pattern instead, like this

  // This part declares a pigment for use
  // in the rust patch texture pattern
  #declare Rusty = pigment {
    granite
    color_map {
      [ 0 rgb <0.2, 0, 0> ]
      [ 1 Brown ]
    }
    frequency 20
  }
  // And this part applies it
  // Notice that our original layered texture
  // "Speckled_Metal" is now part of the map
  #declare Rust_Patches = texture {
    bozo
    texture_map {
      [ 0.0  pigment {Rusty} ]
      [ 0.75 Speckled_Metal ]
      [ 1.0  Speckled_Metal ]
    }
  }

And the ultimate effect is the same as if we had layered the rust patches on to the speckled metal anyway.

With the full array of patterns, pigments, normals, finishes, layered and special textures, there is now practically nothing we cannot create in the way of amazing textures. An almost infinite number of new possibilities are just waiting to be created!