Scatter

../_images/pgYeti_scatter1.png

The Scatter node is used to randomly scatter particles over the input geometry, the various parameters and inputs can be used to limit the location/density of the scattered points as well as how evenly they are spaced. If a second input is connected this may have an attribute used to control the density of the particles, by default Scatter looks for an attribute named density but any can be used, as long as the Groom/Texture Attribute parameter is set correctly.

A Texture node may be use prior to the Scatter node to control the density via a painted image - this is treated as a special case and the name of the Attribute created in the Texture node will need to be set in the Groom/Texture Attribute vs. referenced in a parameter expression.

Note

The reason why the Texture node attribute can’t be referenced in the same way is that up until the point of the Scatter node no geometry has existed, so the attribute at this stage is a placeholder vs. fully sampled.

Inputs

Input Description
0 Data Flow Fibres
1 Strands Groom/Guide Curves which may have an attribute painted to control the density

Scatter

Parameter Description
Density Multiplier a density value is usually defined between 0-1, if you have an input Groom to control the density this is usually the case. This value is a multiplier on top of the base density.
Density the density, based on input area. This is overridden if Input 1 is connected.
Lock Density in some cases ( such as with clumping ) you need to make sure a specific density is retained even if rendering, this will make sure the Scatter node produces the same points regardless of the Display and Render densities.
Seed a random seed value used to generate the points and also passed through the flow to any other connected nodes that may require random number evaluation.
Groom/Texture Attribute the attribute that defines the density of the points if Input 1 is connected or the incoming flow has a Texture attribute pre-defined
Source Objects if more than one mesh is imported up stream this provides a means of generating points either on the first mesh, or all of them.
Face Set limits the creation of source points to faces only contained within the named face set ( if it exists ).

Fibres

Parameters to control how the Scatter node behaves with input Fibres.

Parameter Description
Base/Tip Density Will modulate the density of the scattered particles along the length of the input fibre.
Up Vector Is used with the tangent of the input fibre to compute a decent random normal for the resulting particles.

Distribution

Parameters to control the distribution of the points more closely.

Parameter Description
Relax Steps By default Scatter creates fairly random points, by increasing the relaxation steps the points relax their positions which result in a more even and regular distribution ( which is generally what you need for feathers ).
Obey Face Set Toggles whether the relax process is contained within the defined face set or not.

Warning

Relax Steps can be a slow procedure and is only recommended for feathers and instances where there are generally fewer points and a clean placement is more desirable. Using this with fur/hair would make a negligible difference to the look for a potentially massive increase in computation time.

Example

Maya File: examples/yeti_textureExample.ma