TABLE OF CONTENTS
Attribute
Blend
Displacement
Group
Merge
Shader
Switch
Transform

Attribute

The Attribute node is used to create or promote attributes in the flow. New attributes can be used to control parameters via expressions or to pass information to the renderer via mapping.

Input	Type	Description
0	Data Flow	Particles, Fibres, Feathers and Meshes
1	Strands	Groom/Guide Curves which may have an attribute painted to be sampled.

Parameter	Description
Attribute	The name of the attribute, if it already exists then it will be modified - otherwise it will be created.
Default	Default value for the attribute.
Attribute Type	The data type for the new attribute.
Detail Type	Constant = Per Object, Uniform = Per Element, Varying = Per Span and Vertex = Per Vertex.

Mapping

Attribute mapping is a way of telling Yeti that the desired attribute needs to be passed to the rendering engine, possibly to be used for shading or to control renderer specific parameters.

Parameter	Description
Map As Renderable Attribute	This will map a named attribute to a renderable attribute. If on Yeti will output either the new attribute or an attribute specified below to the renderer.
Attribute	The name of the attribute to map.
Mapping	The name of the attribute as it should be passed to the renderer, if left blank it will use it’s current name.

Groom

Yeti grooms allows users to paint additional attributes across the strands, these groom attributes can then be sampled by the Attribute node to set new attribute values.

Parameter	Description
Sample Groom	Toggle on/off (default) groom sampling.
Groom Attribute	The name of the attribute on the groom to use for sampling.
Interpolate Samples	Controls whether the grooms samples will interpolate multiple strand values (default) or just consider a single closest strand.

Geometric

Helper parameters to create geometry based attributes that rely on the topology of the incoming data.

Parameter	Added Attribute	Description
Add Reference Position	PRef	This will store the current position as a PRef vector attribute.
Add Root Position	surf_P	Will create a Yeti attribute called `root` which will be passed to the render engine as `surf_P`. This is a vector that represents the base of the fibre.
Add Tangent	tangent	Tangent of the fibre at the vertex being evaluated.
Add Face Index	faceindex	Index of the face the fibre/particle was create.
Add Per Vertex Texutre Coordinates	vtxcoord	Baked input mesh facevarying texture coordinates into per vertex values.
Add Arc Length	arcLength	Computed the arc length the input fibres.
RiCurve Basis	N/A	Can be used to control what basis function is used when exporting the curves to a Renderman compliant renderer.

Blend

Blend takes two similar flows and blends them together, Blend is very specific about how similar the two flows need to be and in some cases will fail if the data is too dissimilar.

Input	Type	Description
0	Data Flow	Fibres
1	Strands	Fibres

Parameter	Description
Blend	The amount to mix the second input into the first.
Blend Random	Used to randomize the amount that the two inputs are blended together.

Displacement

The Displacement node is used to displace, or push, particles and fibres along the specified direction. This is useful for matching render time displacement if a Texture node is referencing a similar map or for creating interesting effects using an expression in the Amount parameter.

Input	Type	Description
0	Data Flow	Fibres and Particles

Parameter	Description
Weight	The weight of the displacement.
Amount	The amount to displace by.
Direction	The direction of the displacement, $N is a good default as it follows the normal of the surface the geometry was created from but it can be any vector value.

Group

The Group node is used to create groups that can later be used to limit the effect of specific nodes. If you have Display Feedback on with this node displayed Yeti will highlight the points currently being grouped.

Example: Group Node Example

Input	Type	Description
0	Data Flow	Fibres, Particles or Mesh
1	Data Flow	Mesh

Parameter	Description
Group Name	The name for the new group.
Mode	Bounding Volume uses Origin and Radius to determine a spherical volume Bounding Object uses the geometry from Input 1 to determine the grouping Expression uses Expression to choose if a point is in the group or not.
Origin	when Bounding Volume has been selected this determines the origin of the volume.
Radius	when Bounding Volume has been selected this will define the radius of the spherical volume.
Expression	when Expression has been selected this will be expression that is evaluated - if the result is true then the point will be included in the group. eg. “$P[1] > 0.5” will result in all the points with a Y location more than 0.5 being grouped.
Sidedness	whether to consider points inside/below the surface or outside/above the surface as being grouped. If Close To Surface is selected it will use the points relationship to the actual surface to determine if it should be in the group or not.
Distance From Surface	When Close To Surface is chosen for Sidedness this determines how far from the surface the point can be to be considered in the group.
Attribute	what attribute should be evaluated, in most cases this is P but you may with to use Pref or N to group based on the direction of the normal etc.

Merge

Merge is used to merge two flows together into one flow and you can have as many Merges as needed to bring together any number of flows.

The node supports a dynamic number of inputs which can be controlled with the Number of Inputs parameter, the default is 2.

Input	Type	Description
0	Data Flow	All geometry.
x	Data Flow	All geometry.

Parameter	Description
Number of Inputs	Used to sent the number of desired inputs for the node.

Shader

The Shader node is used to create/set attributes in the flow that will be passed to the Renderer to control various shading parameters. The parameters match the Renderman shader that ships with Yeti thus is very specific to that shader and the Renderman renderer although the attributes may be accessed by the other renderers using custom UserScalar/Float/Color/Vector nodes.

Historically this node was specific to a reference Renderman shader that shipped with earlier releases of Yeti - some of the parameters may change to reflect a more general shading interface.

Input	Type	Description
0	Data Flow	Fibres and Particles

Parameter	Description
Color	Toggle whether to set/override the color attribute
Diffuse Color	The desired diffuse colour.
Adjust HSV	Toggle whether to set/override the HSV value.
HSV Adjustment	The desired HSV offset.
Color Shift	Toggle whether to set/override Color Shift.
Max Hue Shift	The maximum amount the hue may shift if Color Shift is on.
Max Saturation Shift	The maximum amount the saturation may shift if Color Shift is on.
Max Value Shift	The maximum amount the value may shift if Color Shift is on.
Occlusion	Toggle whether to set/override occlusion.
Occlusion Color	The desired occlusion color.
Opacity	Toggle whether to set/override opacity.
Base/Tip Opacity	Desired base/tip opacity.
Specular	Toggle whether to set/override specular.
Ks	The desired Ks value.
Specular Color	The desired specular color.

Switch

The Switch node is a simple (but powerful) utility which can be used to control what input stream is passed through to the output.