Collision over-simplification in RST

Hello,

I am working with MATLAB to visualize the collision meshes of a robot I've designed. When using the show(robot) function, I notice that the collision meshes appear less detailed, I guess, the idea is to optimize execution time and reduce CPU load.

Could you please provide information on the maximum number of triangles allowed per STL file for collision meshes? I aim to achieve a balance between having detailed collision meshes and maintaining computational efficiency.

How it's supposed to look like :

meshTri = stlread("concept_c-bras5_col.stl");
trisurf(meshTri)
axis equal

How it actually looks like :

rbt = importrobot("concept.urdf");
show(rbt,Collisions="on");

As you can see it's really ugly. Do you know how to improve the collision meshes make them more accurate ?

Answer 1

[Githin John]

Hello,

You are seeing this over-simplification because it makes use of the convex hull of the available mesh, as we need a convex mesh for the collision check.

You could make use of convex decomposition of your mesh to get a more represntative collision mesh.

robotCollisionDecomp = importrobot("concept.urdf",CollisionDecomposition=true);

You can check this link to see more details about how to customize the decomposition of your mesh.

Alternatively, you could use collisionVHACD to decompose just the required mesh.

meshTri = stlread("concept_c-bras5_col.stl");

decomposedMesh = collisionVHACD(meshTri);

showCollisionArray(decomposedMesh);

Then clear the approximated collision mesh from the rigidBody and replace with the decomposed one.

rbt.Bodies{indexOfBody}.clearCollision;

for i=1:numel(decomposedMesh)

rbt.Bodies{indexOfBody}.addCollision(decomposedMesh{i})

end

More details here.

[Denizhan AKINCI]

It works. Thank you!