Landscape

Landscape is a highly versatile shader that helps to map textures to terrain and other types of complex models in useful and natural ways, through attributes such as slope, height, image, and noise functions. For example, on a single piece of terrain geometry it could be used to create dusty pile-ups on plateau surfaces, exposed rock faces in steeper cliff-like areas, and water stains where the ground meets the sea. Especially useful in situations where the size or shape of an object makes handmade textures impractical.

Landscape works by dynamically replacing a texture's alpha channel - making its blending more or less opaque according to the effects of the parameter settings.


Procedure

In the texture dialogue box select a texture image which has an alpha-channel.

Select Alpha Channel Mask for the texture's blending.

Select the Landscape shader as the texture shader, and edit its parameters.


Effects

The artist controls Landscape by applying one or more different "effects". One such effect, Slope, piles a texture on flat surfaces, like snow piling on a plateau. Height behaves like a waterline. Two different noise generators, Shape Based and Position Based, provide natural-looking irregularities. Stain allows the artist to confine a texture with the boundaries of another object. Image allows the texture's own color or alpha-channel to influence its blending.

Landscape's real strength comes from allowing the artist to mix these effects. An example is mixing Slope and Height to give snow on high peaks. We'll explore mixing in detail later.


Parameters

Overall

Relative to controls whether the positions and angles are measured from the World Center or the Object Center. World Center is good in situations where several different objects need a texture to line up across all the objects. Object Center is useful when an object needs to move, and the texture must move with it. Also, by rotating the center in Object Center mode, effects can be applied at an angle other than the horizontal.

Blur controls the sharpness of the border between the opaque and transparent extremes of the alpha-channel. A value of 0 gives a sharp line, a value of 1 gives a very blurred line.

Preview Color

When mixing several Landscape layers, it can be to difficult see where one texture ends and another begins, especially if the textures are very similar. Preview Color allows the artist to temporarily replace the texture with a bright solid color, so that the borders of the effects can be clearly seen.

Slope Effect

The Slope Effect acts like snow piling on a plateau. Flatter areas receive an opaque alpha-channel while steep areas receive a transparent alpha-channel.

Angle specifies where the cutoff line is, (i.e. how steep the slope is before the snow begins falling off) measured in degrees from the XZ plane.

Upside Down reverses the direction of the effect, so that the alpha-channel is opaque in steep areas and and transparent in flat areas.

Influence is used for mixing, see below.

Height Effect

The Height Effect creates a horizontal line across the object; areas above the line receive an opaque alpha-channel, areas below receive a transparent alpha-channel.

Height specifies how high the line should be, expressed in SoftImage units; the line is measured either from the object's center or from the world center, according to the settings in Overall: Relative to (see above).

Spread tells how wide the area of effect should be, for blurring and mixing with other effects.

Upside Down reverses the direction, so that the alpha-channel is opaque below the height-line and transparent above it.

Influence is used for mixing, see below.

Position Based Noise and Shape Based Noise

The two noise generators provide a way to insert randomness into the landscape. Position Based Noise is the noise generator most people are familiar with; it is based upon the surface's absolute position in space. Unfortunately, the noise isn't effected by the shape of the surface, and so can sometimes produce an unnatural pattern.

Shape Based Noise helps alleviate this problem by using the shape exclusively as the seed for the noise. This means that as the surface dips and curves, Shape Based Noise will give variations that reflect the change. The drawback comes when two objects have the same shape, they will have the same noise; or when a surface is flat, it will receive no noise.

A good effect can often be achieved by mixing Position Based and Shape Based noises.

Scale controls the size of the largest clumps of noise. For Position Based Noise, Scale is measured in SoftImage units. For Shape Based Noise, Scale is measured in degrees.

Roughness controls how jagged the edge of the noise is. A value of 0 gives a smooth edge, while a value of 1 gives a rough, speckled edge.

Coverage controls what percentage of the overall alpha-channel is opaque. A value of 0 gives 50% opaque areas, 50% transparent areas. Smaller values give less opaque ares, larger values give more opaque areas.

Y-Scale lets the artist stretch the noise in the Y direction. A value less than 1 compresses the noise in the Y direction, giving an appearance similar to sedimentary rock; a value greater than 1 stretches the noise in the Y direction, giving a appearance similar to dripping stains.

Influence is used for mixing, see below.

Stain Effect

The Stain Effect works in conjunction with the Stain shader. Any area of the texture contained by a staining object will receive an opaque alpha-channel, while areas outside the staining object will receive a transparent alpha-channel.

Thickness is used to control how far a point must lie within the staining object before the alpha-channel becomes opaque.

WARNING: This thickness is determined by the viewing angle. Large values for the thickness can cause the texturing to change as the object or camera change their relative position in the scene; this can be particularly undesirable in animation sequences.

Influence is used for mixing, see below.

Image Effect

The Image Effect uses the texture itself to effect the alpha channel. Any combination of the red, green, blue, or alpha channels can be used. Values in the image above 0.5 will give an opaque alpha-channel, while values below 0.5 give a transparent alpha-channel.

Influence is used for mixing, see below.

Mixing Effects

A wide variety of patterns can be achieved by mixing these effects together. Mixing is accomplished by adjusting the Influence slider in each of the active effects. An effect with a high Influence value will tend to dominate the other effects; an effect with a low Influence value will only subtly modify the other effects. When specifying Influences, the ratio of the influences is all that is important.

For example, by mixing Height with a small amount of Position Based Noise, we get a roughened Height line. But if we begin turning up the Influence of the noise, the line breaks up. At high enough values, we can't distinguish the line; all we can tell is that the noise is thicker at the top.

Another example is the mixture of Height and Slope. With a high Influence for the Height, we get a nearly horizontal line with small dips for flat areas. As the Influence of the Slope increases height becomes less important, and the texture tends to cling to to flat areas.