Houdini 20.0 What’s new What’s new in Houdini 19.5

What’s new Muscles & Tissue

This feature is still under development. The current functionality is unfinished and subject to change, and may have thin or no documentation. Please bear this in mind when using it.

Deform a muscle tetrahedral mesh to match a supplied target shape (polygonal surface) with the new FEM Deform SOP node.
Stiffness values are now more accurately applied to muscles, tissue, and skin with respect to the area of their triangles and the volume of their tetrahedra thanks to the new Scale-Invariant ARAP Vellum method. This improvement affects the following parameters:
- Muscle Properties SOP node’s Shape Stiffness and Fiber Strength parameters.
- Tissue Properties SOP node’s Shape Stiffness parameters (Surface and Solid).
- Skin Properties SOP node’s Shape Stiffness parameters (Surface and Solid).
Specify how much your muscle ends are allowed to move towards their bones with the new Compression Stiffness parameter on the Muscle Constraint Vellum Properties SOP node. This also influences how rigidly muscle ends are held to their bones.
Preserve the initialization connection orientation of your muscles ends to their bones with the new Tangent Stiffness parameter on the Muscle Constraint Vellum Properties SOP node.
Use painted attribute values to increase or decrease the thickness of your tissue layers with the new Thickness Scale Attribute and Scale parameters on the Tissue Solidify SOP node.
Visualize the interior surface or tetrahedral boundary of your Tissue Solid Layer with the new Tissue Interior Surface parameter on the Tissue Solidify SOP node.

Adjust how freely your tissue or skin polygon surfaces can bend with the new Bend Stiffness and Bend Damping Ratios parameters on the Tissue Properties SOP and Skin Properties SOP nodes.
Ignore incoming tissue or skin Volume Stiffness and instead apply an infinite stiffness to the volume of tissue or skin primitives as they change shape with the new ARAP Volume Preservation (Optimized) parameter on the Tissue Solver Vellum SOP and the Skin Solver Vellum SOP nodes. This optimizes the volume preservation that is applied to your tissue and skin. If you want custom control over Volume Stiffness (the Houdini v19 volume behavior), then turn off ARAP Volume Preservation (Optimized).
Specify which rest positions or t-poses your tissue and skin solvers should use when they establish their constraints with the new Rest Position parameters on the Tissue Solver Vellum SOP and Skin Solver Vellum SOP nodes.
Determine whether the attach relationships between your tissue interior surfaces or skin interior surfaces and their respective internal attach geometry are stiff (hard) or springy (soft) with the new Relax Internal Geometry parameters on the Tissue Solver Vellum SOP and Skin Solver Vellum SOP nodes.
Determine how tightly or loosely your rigid points are attached to their bone surfaces and muscle solid geometry with the new Rigid Stiffness and Rigid Damping Ratio parameters on the Tissue Solver Vellum SOP and Skin Solver Vellum SOP nodes.