# rblock dilate command

Syntax

rblock dilate keyword ... <range>

Primary keywords:

Dilate rigid blocks. A rigid block is represented by a core shape that is composed of {linear facets in 2D; triangular facets in 3D}. The core shape is convex, closed and manifold. When rounding is nonzero, the core shape is expanded in all directions by a {circle in 2D; sphere in 3D} of a specified radius with center passing along all points on the exterior of the core shape. The value of the rounding corresponds to the radius of this expansion {circle in 2D; sphere in 3D}. Rounding can result in fewer contacts for highly packed models and in faster contact resolution.

By default, dilating a rigid block means that the core shape remains unchanged and rounding as added to the original core shape. In other words, {corners in 2D; edge and corners in 3D} are rounded and each facet plane is moved outward (i.e., away from the centroid) in the facet normal direction by the rounding distance. This results in a larger rigid block. By default the inertial properties are adjusted to those of a convex {polygon in 2D; polyhedra in 3D} whose faces have been translated outward in the facet normal direction by the rounding distance. If the rigid block is already rounded this rounding is added to the old value.

If the expand keyword is given rounding is not applied. Instead, the rigid block core shape is expanded in such a way that the facet normals are largely unchanged but the facets are moved outward (i.e., in the facet-normal direction) by the specified amount. If the original core shape has a fair degree of radial symmetry and the distance is small compared with the distance from the facets to the centroid, dilation will result in a core shape with the same surface topology (i.e., facet number and connectivity) as the original core shape. In some cases, though, dilation can produce a different topology. In such cases, in order to keep the surface topology unchanged, the principal aspect ratios of the new core shape are computed and the old core shape is stretched in the principal aspect-ratio directions to match the new core shape aspect ratio.

f

The degree of rounding is f.

expand f

Dilate the core shape by f without rounding. By default this is an absolute distance, so all core shapes are dilated by the same amount.

relative

The amount of expansion is computed as the product of f and the radius of a {circle in 2D; sphere in 3D}

with the same size as the rigid block. Thus the expansion varies per rigid block.

keep-inertial

Do not adjust the inertial properties as a result of dilation. This may be advantageous when the rounding distance is small.

relative f

The degree of rounding is computed as the product of f and the radius of a {circle in 2D; sphere in 3D} with the same size as the rigid block.