Houdini 20.0 Nodes Geometry nodes

Skin Solidify geometry node

Converts surface geometry to a solid (tetrahedrons) and prepares the output geometry for solving with a skin solver.

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Since 19.0

This node constructs the Skin pass (Skin Surface Layer and Skin Solid Layer) from an input polygonal surface.

Important Note

Applying a Skin pass to your character is optional. You can achieve many Muscle & Tissue simulation looks with only the Tissue pass. Adding Skin Layers to your character lets you to create finer wrinkling and folding skin effects.

The first input (Input 1) on this node provides the surface geometry from which to generate the Skin pass’s outer polygonal surface (Skin Surface Layer) and its inner tetrahedra (Skin Solid Layer). The surface geometry must be triangulated before tetrahedralization. If the surface isn’t already made of triangles, you can use the Remesh Exterior Surface parameters on this node to triangulate it. For more control over how the surface geometry’s polygons are triangulated, you can use an external Remesh SOP node instead.

In most cases, this node’s Skin Thickness parameter value should match the value of the Surface Inset parameter on the Tissue Solidify SOP node upstream. However, this is not a requirement. The innermost boundary of the Skin Solid Layer is constrained to the Tissue Surface Layer. You can affect how strong and how tight the attach constraint is by modifying the Surface Layer ▸ Attach-type parameters on the Skin Properties SOP node.


You can use an Attrib Paint SOP node to paint a thickness multiplier attribute to customize and vary the skin’s thickness. You can use the Thickness Multiplier Attribute parameter on this node to specify the name of that painted attribute.

Cross section showing the Skin Layers


Skin Thickness

Specifies how deep the Skin Solid Layer (tetrahedral mesh) should be and determines the distance from the Skin Surface Layer to the Tissue Surface Layer. This parameter is also closely related to the Surface Offset parameter on the Tissue Solidify SOP node.


  • If you want the Skin Thickness parameter’s value to be the same as the value of the Surface Offset parameter on the Tissue Solidfy SOP node, then you can create a channel reference by copying the Surface Offset value and pasting it to the Skin Thickness field as a relative reference ( RMB ▸ Paste Relative Reference).

  • when Surface Offset is larger than the Skin Thickness, you can achieve more surface detail and muscle definition as this will cause the the skin to seek out all the crevices.

Thickness Multiplier Attribute

When on, specifies the name of the attribute (skinthickness by default) you can use to vary the thickness of the skin’s tetrahedra. The value of this attribute is a multiplier for the Skin Thickness parameter. You can use an Attrib Paint SOP node to paint this attribute on your character’s skin to vary its thickness in the painted areas.

Regular Layers

Determines how many layers of tetrahedrons are packed into the overall skin thickness.

Weight Attribute

This parameter indicates the name of a point attribute that will be used as a blur weight for the interior surface smoothing. If the arribute is missing or left blank, the smoothing will affect the entirety of the interior surface.

Blurring Iterations

Averaging point positions on the interior surface ot the skin layer can help smooth out imperfections and anomalies. This parameter determines the number of smoothing iterations to apply.

Step Size

Size of each iteration when blurring.

Remesh Surfaces

See the Remesh SOP node’s documentation.

Color Inverted Tets

These color choosers allow you to highlight inverted tetrahedrons. Inverted tetrahedrons, ie. tetrahedrons with a negative voulme, are usually caused by aggressive interior blur settings, and should be avoided.


Input 1

The surface polygons from which to generate the Skin pass (Skin Surface Layer and Skin Solid Layer).


Output 1

Skin pass, which includes the Skin Surface Layer (polygons) and the Skin Solid Layer (tetrahedra).

See also

Geometry nodes