View Full Version : unwanted light through Poly seams

03 March 2004, 08:49 PM
Can anyone tell me how to stop light from coming through the edges of these polygons?

The room is made up of one poly cube. I've tried beveling the edges and even tried to block the light with a scaled up duplicate of the room.

04 April 2004, 02:04 AM
I have similar problems while working with GI in Mental Ray (for a room that gets illumination from the an outside light. No matter how I build my models (e.g. extending the walls, making walls solid etc) I end up with this kind of leak (in my case, photon leaks).
My workaround is to make GI radius small enough so the photons become smaller than the wall width but that prevents me to fine tune my GI results. Other thing that I try is to set the spot angle so it does not hit the corner areas but, again, sometimes it is virtually impossible.
I would surely welcome some help here.

04 April 2004, 08:55 AM
i had just this problem the other day. I ended up making several poly cubes and placing them in front of the seams, between the light and the seam. I also bumped up the subdivisions of the light blocking cubes because that seems to have been the problem with the original object.


04 April 2004, 08:01 PM
Thanks for the help. I'm guessing that the low subdivision count of the model was my main problem, though I managed to fix it by just messing around with the Dmap Shadows settings and the placement of the light.

04 April 2004, 03:31 AM
This is a common problem with low subdivision meshes, where illumination is computed at the verts of the triangles and then interpolated across the triangle even if another mesh intersects it which one would think the light to be blocked, but does not.

When using GI in mental ray, if the wall is thinner than the maximum radius specified by the global illumination accuracy, it can cause the radius to reach through the wall and fetch photons from the other side. You can avoid this by not using zero thickness walls and reducing the maximum accuracy radius, but use caution when adjusting the max accuracy radius because you can get unwanted noise in the scene.

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