I am running into problems due to the lack of csg in radiance. I need to accurately model a tube with a very specular material, which is bent. The real tube is produced by cutting a cylinder under 22.5 degree and assembling it, leading to a nice 45degree angle with one ellyptical edge. As I am not able to cut a cylinder geometry in radiance, I have modeled it as a mesh, but the specularity leads to visible edges.
I have been sonsidering several solutions so far:
1) Using antimatter to cut away parts of the cylinder would probably not work, as the second cylinder, which also has to be cut, would lead to two overlapping antimatter volumes.
2) Refining the mesh would result in huge geometry, as the segments would become thinner while keeping their length, this would lead to a real worst case for oconv. Also to make the edges disappear, I would have to get into dimensions where one facet should not take much more then one pixel in the final rendering.
3) Using "smooth" surface normals would lead to an visual improvement. But I have my doubts if these would be considered for photon mapping and especially caustics? In my setup, the pipe ends with a diffusor (currently modeled as a box modified by a rather generic trans material). I would expect caustic effects to become visible caused by a round tube geometry with very high specularity.
4) The last option I see is using a cylinder object with a mixfunc modifier and a simple cal file containing just the line
condition=if(Pz-Px,1,0);
to cut my geometry in 45 degrees, using void to get parts of the geometry invisible. Would that work with overlapping geometries (which would still exist, even if invisible), and would it be relieable with the pmap extension? The main disadvantage here is that I would have to maintain an extra set of geometry for radiance, while I could use converters to import from other programs so far.
Your idea of applying a mixfunc is clever, and I believe it should work, at least in Radiance "classic". I have no idea if material mixing is supported in the photon mapping extension, however.
Best,
-Greg
···
From: "Lars O. Grobe" <[email protected]>
Date: February 5, 2009 11:21:26 PM PST
Hi,
I am running into problems due to the lack of csg in radiance. I need to accurately model a tube with a very specular material, which is bent. The real tube is produced by cutting a cylinder under 22.5 degree and assembling it, leading to a nice 45degree angle with one ellyptical edge. As I am not able to cut a cylinder geometry in radiance, I have modeled it as a mesh, but the specularity leads to visible edges.
I have been sonsidering several solutions so far:
1) Using antimatter to cut away parts of the cylinder would probably not work, as the second cylinder, which also has to be cut, would lead to two overlapping antimatter volumes.
2) Refining the mesh would result in huge geometry, as the segments would become thinner while keeping their length, this would lead to a real worst case for oconv. Also to make the edges disappear, I would have to get into dimensions where one facet should not take much more then one pixel in the final rendering.
3) Using "smooth" surface normals would lead to an visual improvement. But I have my doubts if these would be considered for photon mapping and especially caustics? In my setup, the pipe ends with a diffusor (currently modeled as a box modified by a rather generic trans material). I would expect caustic effects to become visible caused by a round tube geometry with very high specularity.
4) The last option I see is using a cylinder object with a mixfunc modifier and a simple cal file containing just the line
condition=if(Pz-Px,1,0);
to cut my geometry in 45 degrees, using void to get parts of the geometry invisible. Would that work with overlapping geometries (which would still exist, even if invisible), and would it be relieable with the pmap extension? The main disadvantage here is that I would have to maintain an extra set of geometry for radiance, while I could use converters to import from other programs so far.
Your idea of applying a mixfunc is clever, and I believe it should work, at least in Radiance "classic". I have no idea if material mixing is supported in the photon mapping extension, however.
Best,
-Greg
From: "Lars O. Grobe" <[email protected]>
Date: February 5, 2009 11:21:26 PM PST
Hi,
I am running into problems due to the lack of csg in radiance. I need to accurately model a tube with a very specular material, which is bent. The real tube is produced by cutting a cylinder under 22.5 degree and assembling it, leading to a nice 45degree angle with one ellyptical edge. As I am not able to cut a cylinder geometry in radiance, I have modeled it as a mesh, but the specularity leads to visible edges.
I have been sonsidering several solutions so far:
1) Using antimatter to cut away parts of the cylinder would probably not work, as the second cylinder, which also has to be cut, would lead to two overlapping antimatter volumes.
2) Refining the mesh would result in huge geometry, as the segments would become thinner while keeping their length, this would lead to a real worst case for oconv. Also to make the edges disappear, I would have to get into dimensions where one facet should not take much more then one pixel in the final rendering.
3) Using "smooth" surface normals would lead to an visual improvement. But I have my doubts if these would be considered for photon mapping and especially caustics? In my setup, the pipe ends with a diffusor (currently modeled as a box modified by a rather generic trans material). I would expect caustic effects to become visible caused by a round tube geometry with very high specularity.
4) The last option I see is using a cylinder object with a mixfunc modifier and a simple cal file containing just the line
condition=if(Pz-Px,1,0);
to cut my geometry in 45 degrees, using void to get parts of the geometry invisible. Would that work with overlapping geometries (which would still exist, even if invisible), and would it be relieable with the pmap extension? The main disadvantage here is that I would have to maintain an extra set of geometry for radiance, while I could use converters to import from other programs so far.