Failed photon distribution

radiance-general
1

Hi list,

When I tried to render global and caustic photon maps, I got no global and caustic photons stored due to too many prepasses. Even though I intended to just render a global photon map and reduce the -apD to 0.1, I still got the feedback that shows “fatal-failed photon distribution”. As I only used diffuse materials (plastic) which could redirect the incident light to some other surfaces, why the global photon maps could not be produced successfully?

Thanks,

Clarence

2

Hi Clarence,

if you have really only diffuse surfaces, the caustic photon map cannot be generated. Do you not even have a glass pane in the model?

Did you include a photon port in your model?

Cheers, Lars.

3

Hi Lars,

I know the caustic photon map would not be generated when only using diffuse surfaces. So I only used diffuse materials in the scene and wanted to see whether the global photon map can be generated.

As far as I know a photon port seems not to be used necessarily if I only test a light source in an interior space (please correct if it is wrong).

Best,

Clarence

4

Hi Clarence,

ok, so you have a “box” with a light source? How is the light source modeled? Do you get reasonable results without the photon map? What are the reflection properties of the box walls?

Cheers, Lars.

5

Hi Clarence,

thanks for bringing this up. There are a number of conditions that may prevent photons from being deposited. I take it at least one of the diffuse surfaces has a line of sight (either direct or via some transparent medium) to the light source, as would be expected in an interior. Are you using a brightfunc or some other modifier with the light source? Basically I need some more info on your scene to figure this out.

Thanks and best regards,

–Roland

6

Hi Lars and Roland,

The problem of generating global and caustic photon maps in an interior space using an electric light source was resolved. It was just about the sampling mechanism of my mac OSX system.

Best,

C

7

Hi Roland,

I tried to get irradiance distribution from a source with modifier src1, but I got such feedback “caustic photon map does not support contributions” when I executed the following command:
#cat testpoints.pts | rcontrib -I -h -V -o p_%s.dat -m src1 -ap caustic.cpm 1000 src1.oct < sun.pos
Any critical problems with this command?

Thanks,

Clarence

8

Hi Clarence,

rcontrib only accepts contribution photon maps generated with mkpmap’s -apC option. This is a unified photon map similar to the global photon map, and thus includes specular scattering as well; it cannot be combined with a separate caustic photon map. Infact, you can render a contribution photon map with rpict, in which case it will behave exactly like a global photon map. Hope makes the (admittedly confusing) distinction a bit clearer.

Best regards,

–Roland

9

Hi Roland,

I did it so, but I found that the bandwidth specification would affect the result. How should I guarantee the results, although the bandwidth could be increased to a higher value according to the photon map user manual.

Regards,

Clarence

10

Hi Clarence,

you need a contribution photon map for this, not the caustic photon map.
Please refer to:

Cheers, Lars.

11

Hi Lars,

Thanks for the suggestions.

I finally replaced caustic.pm with contribution.pm according to the manual and wanted to see how the annual simulation with contribution photons will be when using rcontrib.

For example, I took a reference to the relevant slides from Radiance workshop 2015 and used the following command:
#makmap -apC contrib.pm 100k a.oct (%a.oct contained a scene and three solar patches for test.)
#rcontrib -I+ -h -V -o p_%s.dat -m solar -ap contrib.pm 365 a.oct < calculationpoint.txt
It returned me just a p000.dat. How to dctimestep to obtain the sensor illuminance?

Did I miss something?

Thanks,

Clarence