[opensource-dev] Review Request: Allow objects to have 99.99% max hollow for default hollow shape.

[Argent Stonecutter]

On 2011-07-11, at 23:05, Dahlia Trimble wrote:

> One thing I noticed while coding collision geometry for OpenSimulator is as hollow is increased and prims are twisted or otherwise manipulated such that the hollow shape doesnt exactly follow the outer shape, the probability increases that the surfaces formed by the triangles that make up the hollow shape may actually protrude beyond those that make up the outer surface. I'm not sure what SL sims do under these conditions but what ODE (Open Dynamics Engine - most commonly used physics engine in OpenSimulator) is create a condition where physical objects may become trapped between the resulting surfaces. ODE uses trimesh colliders and surface normals for determining collision surfaces and if prim hollow surfaces protrude outside of prim outer surfaces, the surface normals for these surfaces point in the wrong direction. This can be alleviated by increasing prim vertex count, but for some of these prims vertex count may already be even greater than 4000 vertices. Increasing it further would use excessive memory and likely increase the cost of computing collisions dramatically. I've found that a limit of 95% maximum hollow is a good compromise between prim complexity and usability. 
> 
> 
> On Mon, Jul 11, 2011 at 7:34 PM, Wolfpup Lowenhar <wolfpup67 at earthlink.net> wrote:
> This is an automatically generated e-mail. To reply, visit: http://codereview.secondlife.com/r/388/
> 
> Review request for Viewer.
> By Wolfpup Lowenhar.

Given the possible uses of this capability, it would be acceptable for the physics shape to pin at 95% while the rendered shape is allowed to be thinner.