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For the Muscles & Tissue system, muscles are required to be solid tetrahedral structures, but input surfaces do not need to be tessellated as triangles since the Muscle Solidify SOP node will automatically convert your surfaces to triangles using its Remesh Surfaces settings or its internal default remesh mechanism.
However for best results, we recommend that you use an external Remesh SOP node to convert your input surfaces to triangles before tetrahedralization because it has additional parameters that control tessellation quality that the Muscle Solidify SOP node does not have.
Measures and stores the outer thickness (layer of tets) of the muscle’s tetrahedra. This is used by the muscle constraints to vary how strong an attachment is.
Measures and stores the thickness of the entire muscle. This is used by the muscle properties like Thickness Threshold to determine what parts of a muscle are tendon.
Sets and stores the rest position or t-pose pose for the muscles.
Max Tet Size
Sets the upper size limit for individual generated tetrahedrons. The volume of a regular tetrahedron is determined by its side length. Max Tet Size specifies this side length, and as a result determines the maximum volume of the tetrahedra generated by the Muscle Solidify SOP.
The size of a muscle’s surface triangles does not necessarily determine the size of its interior tets. A muscle can have larger surface triangles and smaller interior tetrahedrons depending on the current Max Tet Size setting.
For example, in the images below, the surface triangles remain constant while the size and number of the interior tetrahedrons change depending on the Max Tet Size setting.
Specifies which muscle geometry pose to use as its rest position or t-pose. Your muscles need to be at their t-pose positions when they are tetrahedralized.
Use Initialization Frame
Use the muscle geometry’s pose at the specified Initialization Frame.
Use the muscle geometry pose defined by the specified T-Pose Attribute.
Specifies the frame at which to evaluate the input muscle geometry and hold it static while it is converted into a tetrahedral mesh. By default, the initialization frame is set to the first frame of your playback bar’s range (
This parameter is only available when T-Pose is set to Use Initialization Frame.
Specifies the name of the attribute that contains the t-pose at which to evaluate the input muscle geometry and hold it static while it is converted into a tetrahedral mesh. By default, this attribute is
This parameter is only available when T-Pose is set to From T-Pose.
When on, the node will try to tetrahedralize all your muscles at the same time up by assigning one
muscle_id per thread up to the capacity of your system’s multithreading capabilities. This method is a lot faster than the sequential method. Enable Multithreading is on by default.
When off, the node goes muscle-by-muscle and tetrahedralizes each muscle one at a time. This operation in performed sequentially by
muscle_id in a loop and it will wait to complete one muscle’s tetrahedralization before moving on to the next.
When on, converts the input muscle surfaces into triangles.
The Remesh Surfaces parameters control the size and number of each muscle surface’s triangles.
The minimum target edge length of the triangles on the exterior of the muscle pieces. Increasing this value makes the triangles bigger.
The maximum target edge length of the triangles on the exterior of the muscle pieces. Decreasing this value makes the triangles smaller.
Determines the number and size of the triangles on the exterior of the muscle pieces. A higher value produces triangles that are both smaller and greater in number. Values less than 1 have a decimating/coarsening affect on the exterior of the muscle pieces. Gradation also lessens the affect of Relative Density.
The rate at which edge lengths are allowed to change from one surface triangle to the next. Higher values generate fewer triangles, but they also lower the overall quality of muscle piece exteriors.
The muscle geometry to convert from surfaces to tetrahedral meshes.
muscleid attribute or the
tpose attribute are not present on the input muscle geometry, then the Muscle Solidify SOP will:
tposeattribute and set its value to the geometry’s pose at the Initialization Frame.
muscle_idattributes for each connected cluster of primitives (muscle) on the input geometry and assign them a default muscle ID (for example,
muscle_2, and so on).
Static tetrahedral meshes for each muscle.
maxthicknesspoint attribute and the