The Shader Falloff
This is an additional falloff for particle modifiers. Its use is not restricted to X-Particles; it can also be used elsewhere in Cinema 4D if required.
The falloff appears in the Falloff tab of any object in Cinema which can use falloffs. To use it, select 'xpShaderFalloff' from the 'Shape' drop-down menu in the Falloff tab. The available settings are shown here:
The falloff works by sampling the shader colour at the particle's position in the falloff's field of effect, and returns a value ranging from 0 (if the colour is black) to 1 (if the colour is white). For non-monochrome colours, the average colour brightness value is used, so for example pure red would return a falloff value of 0.33.
This drop-down has three options:
The falloff is not restricted in size but works across the entire 3D world (equivalent to choosing 'Infinite' from the 'Shape' menu).
The falloff has the shape of a box. Its size can be adjusted with the drag handles in the editor, or by changing the 'Size' values in the main falloff tab.
The falloff is spherical. Its size can be adjusted with the drag handles in the editor, or by changing the 'Size' values in the main falloff tab. Note that only the first of the 'Size' values has any effect, the others are not used.
The shader to use. You can use a bitmap if desired, but any channel shader will work. Some, of course, will produce better or more predictable results than others. You can scale a bitmap or (some) shaders by using a Layer shader with a Transform effect added.
If there is no shader in this field, the modifier will have no effect.
Note: due to a limitation in the Cinema 4D falloffs, if you use a bitmap in this falloff it MUST have an absolute path, not a relative path. If it has a relative path the falloff will consistently return a value of zero and the modifier will have no effect.
This switch simply inverts the colour of the bitmap or shader, so white areas are regarded as black and vice versa.