Reference:Pattern Modifiers

Pattern modifiers are statements or parameters which modify how a pattern is evaluated or tells what to do with the pattern. The complete syntax is:

PATTERN_MODIFIER:
  BLEND_MAP_MODIFIER | AGATE_MODIFIER | DENSITY_FILE_MODIFIER |
  QUILTED_MODIFIER | BRICK_MODIFIER | SLOPE_MODIFIER |
  noise_generator Number| turbulence <Amount> |
  octaves Count | omega Amount | lambda Amount |
  warp { [WARP_ITEMS...] } | TRANSFORMATION
BLEND_MAP_MODIFIER:
  frequency Amount | phase Amount | ramp_wave | triangle_wave |
  sine_wave | scallop_wave | cubic_wave | poly_wave [Exponent]
AGATE_MODIFIER:
  agate_turb Value
BRICK_MODIFIER:
  brick_size Size | mortar Size 
DENSITY_FILE_MODIFIER:
  interpolate Type
SLOPE_MODIFIERS:
  <Altitude> 
  <Lo_slope,Hi_slope>
  <Lo_alt,Hi_alt>
QUILTED_MODIFIER:
  control0 Value | control1 Value
PIGMENT_MODIFIER:
  PATTERN_MODIFIER | COLOR_LIST | PIGMENT_LIST |
  color_map { COLOR_MAP_BODY } | colour_map { COLOR_MAP_BODY } |
  pigment_map{ PIGMENT_MAP_BODY } | quick_color COLOR |
  quick_colour COLOR
COLOR NORMAL_MODIFIER:
  PATTERN_MODIFIER | NORMAL_LIST |
  normal_map { NORMAL_MAP_BODY } | slope_map{ SLOPE_MAP_BODY } |
  bump_size Amount
TEXTURE_PATTERN_MODIFIER:
  PATTERN_MODIFIER | TEXTURE_LIST |
  texture_map{ TEXTURE_MAP_BODY }
DENSITY_MODIFIER:
  PATTERN_MODIFIER | DENSITY_LIST | COLOR_LIST |
  color_map { COLOR_MAP_BODY } | colour_map { COLOR_MAP_BODY } |
  density_map { DENSITY_MAP_BODY }

Default values for pattern modifiers:

dist_exp        : 0
falloff         : 2.0
frequency       : 1.0
lambda          : 2.0
major_radius    : 1
map_type        : 0
noise_generator : 2
octaves         : 6
omega           : 0.5  
orientation     : <0,0,1>
phase           : 0.0
poly_wave       : 1.0
strength        : 1.0
turbulence      : <0,0,0>

The modifiers PIGMENT_LIST, quick_color, and pigment_map apply only to pigments. See the section Pigment for details on these pigment-specific pattern modifiers.

The modifiers COLOR_LIST and color_map apply only to pigments and densities. See the sections Pigment and Density for details on these pigment-specific pattern modifiers.

The modifiers NORMAL_LIST, bump_size, slope_map and normal_map apply only to normals. See the section Normal for details on these normal-specific pattern modifiers.

The TEXTURE_LIST and texture_map modifiers can only be used with patterned textures. See the section Texture Maps for details.

The DENSITY_LIST and density_map modifiers only work with media{density{..}} statements. See the section Density for details.

The agate_turb modifier can only be used with the agate pattern. See the section Agate for details.

The brick_size and mortar modifiers can only be used with the brick pattern. See the section Brick for details.

The control0 and control1 modifiers can only be used with the quilted pattern. See the section Quilted for details.

The interpolate modifier can only be used with the density_file pattern. See the section Density File for details.

The general purpose pattern modifiers in the following sections can be used with pigment, normal, texture, or density patterns.

Transforming Patterns

The most common pattern modifiers are the transformation modifiers translate, rotate, scale, transform, and matrix. For details on these commands see the section Transformations.

These modifiers may be placed inside pigment, normal, texture, and density statements to change the position, size and orientation of the patterns.

Transformations are performed in the order in which you specify them. However in general the order of transformations relative to other pattern modifiers such as turbulence, color_map and other maps is not important. For example scaling before or after turbulence makes no difference. The turbulence is done first, then the scaling regardless of which is specified first. However the order in which transformations are performed relative to warp statements is important. See the section Warps for details.

Frequency and Phase

The frequency and phase modifiers act as a type of scale and translate modifiers for various blend maps. They only have effect when blend maps are used. Blend maps are color_map, pigment_map, normal_map, slope_map, density_map, and texture_map. This discussion uses a color map as an example but the same principles apply to the other blend map types.

The frequency keyword adjusts the number of times that a color map repeats over one cycle of a pattern. For example gradient covers color map values 0 to 1 over the range from x=0 to x=1. By adding frequency 2.0 the color map repeats twice over that same range. The same effect can be achieved using scale 0.5*x so the frequency keyword is not that useful for patterns like gradient.

However the radial pattern wraps the color map around the +y-axis once. If you wanted two copies of the map (or 3 or 10 or 100) you would have to build a bigger map. Adding frequency 2.0 causes the color map to be used twice per revolution. Try this:

pigment {
  radial
  color_map{
    [0.5 color Red]
    [0.5 color White]
    }
  frequency 6
  }

The result is six sets of red and white radial stripes evenly spaced around the object.

The float after frequency can be any value. Values greater than 1.0 causes more than one copy of the map to be used. Values from 0.0 to 1.0 cause a fraction of the map to be used. Negative values reverses the map.

The phase value causes the map entries to be shifted so that the map starts and ends at a different place. In the example above if you render successive frames at phase 0 then phase 0.1, phase 0.2, etc. you could create an animation that rotates the stripes. The same effect can be easily achieved by rotating the radial pigment using rotate y*Angle but there are other uses where phase can be handy.

Sometimes you create a great looking gradient or wood color map but you want the grain slightly adjusted in or out. You could re-order the color map entries but that is a pain. A phase adjustment will shift everything but keep the same scale. Try animating a mandel pigment for a color palette rotation effect.

These values work by applying the following formula

New_Value = fmod ( Old_Value * Frequency + Phase, 1.0 ).

The frequency and phase modifiers have no effect on block patterns checker, brick, and hexagon nor do they effect image_map, bump_map or material_map. They also have no effect in normal statements when used with bumps, dents, quilted or wrinkles because these normal patterns cannot use normal_map or slope_map.

They can be used with normal patterns ripples and waves even though these two patterns cannot use normal_map or slope_map either. When used with ripples or waves, frequency adjusts the space between features and phase can be adjusted from 0.0 to 1.0 to cause the ripples or waves to move relative to their center for animating the features.

Waveforms

POV-Ray allows you to apply various wave forms to the pattern function before applying it to a blend map. Blend maps are color_map, pigment_map, normal_map, slope_map, density_map, and texture_map.

Most of the patterns which use a blend map, use the entries in the map in order from 0.0 to 1.0. The effect can most easily be seen when these patterns are used as normal patterns with no maps. Patterns such as gradient or onion generate a groove or slot that looks like a ramp that drops off sharply. This is called a ramp_wave wave type and it is the default wave type for most patterns. However the wood and marble patterns use the map from 0.0 to 1.0 and then reverses it and runs it from 1.0 to 0.0. The result is a wave form which slopes upwards to a peak, then slopes down again in a triangle_wave. In earlier versions of POV-Ray there was no way to change the wave types. You could simulate a triangle wave on a ramp wave pattern by duplicating the map entries in reverse, however there was no way to use a ramp wave on wood or marble.

Now any pattern that takes a map can have the default wave type overridden. For example:

pigment { wood color_map { MyMap } ramp_wave }

Also available are sine_wave, scallop_wave, cubic_wave and poly_wave types. These types are of most use in normal patterns as a type of built-in slope map. The sine_wave takes the zig-zag of a ramp wave and turns it into a gentle rolling wave with smooth transitions. The scallop_wave uses the absolute value of the sine wave which looks like corduroy when scaled small or like a stack of cylinders when scaled larger. The cubic_wave is a gentle cubic curve from 0.0 to 1.0 with zero slope at the start and end. The poly_wave is an exponential function. It is followed by an optional float value which specifies exponent. For example poly_wave 2 starts low and climbs rapidly at the end while poly_wave 0.5 climbs rapidly at first and levels off at the end. If no float value is specified, the default is 1.0 which produces a linear function identical to ramp_wave.

Although any of these wave types can be used for pigments, normals, textures, or density the effect of many of the wave types are not as noticeable on pigments, textures, or density as they are for normals.

Wave type modifiers have no effect on block patterns checker, brick, object and hexagon nor do they effect image_map, bump_map or material_map. They also have no effect in normal statements when used with bumps, dents, quilted, ripples, waves, or wrinkles because these normal patterns cannot use normal_map or slope_map.

Noise Generators

There are three noise generators implemented. Changing the noise_generator will change the appearance of noise based patterns, like bozo and granite.

• noise_generator 1 the noise that was used in POV_Ray 3.1
• noise_generator 2 range corrected version of the old noise, it does not show the plateaus seen with noise_generator 1
• noise_generator 3 generates Perlin noise