Fatness¶
There are several areas where problems can occur when cloth Fatness/thickness is not set properly.
Self-collision Fatness/Tessellation Ratio¶
When Carbon Cloth and Carbon Morph are self-colliding, then Carbon internally uses a fatness value that is called the Inter Fatness.
The Inter Fatness is not specified by the user but automatically calculated. It is the largest fatness value that the geometry’s smallest triangle can accommodate without causing triangles to collide with their close neighbors (collision between two triangles sharing the same edge is disabled, but triangles still have collision enabled with theirs neighbors’ neighbors).
As the Outer Fatness value sets the thickness for collision, it is important to understand that the Outer Fatness will not be respected if the Inter Fatness is less than the Outer Fatness.
The Carbon Cloth Guide Geometry provides a Fatness Check tool to help show the problem areas. It will show triangles in red (worst) yellow (not great) that will trigger an Inter Fatness that is smaller than the set Outer Fatness. In order to hit the required thickness during self-collision you have to make the geometry’s smallest triangles bigger, until they no longer show up as red/yellow in the Fatness Check tool.
Fatness check.
Note
As this only concerns self-collision, when the Self Collide flag is not set this problem can be safely ignored.
Distance Between Geometry¶
If the distance between two parts of the same Carbon Cloth, e.g. in folds or layers, is smaller than twice the fatness, or if the distance between two Carbon objects is smaller than the sum of the fatness values, then a non inter-penetrating geometry can become inter-penetrating within the simulation. This can then lead to an overconstrained situation and in the worst cases can cause the simulation to blow up.
Two non-overlapping geometries.
Since all Carbon dynamic objects have got fatness, it can be tricky to set up geometry in a way that there are no overlaps in the simulation. The two geometries in the screenshot above do not overlap or contact each-others at a geometry level, but however they intersect in Carbon due to their fatness.
The Carbon Cloth Guide Geometry provides a Double Sided drawing to show the true extensions of the Carbon Cloth or Carbon Morph.
Note
The Front Offset and Back Offset are not set automatically. Manually copy the Fatness value from the Parameters to display the right information.
Double sided drawing shows that the collision volumes overlap.