Trans Rendering Issue

radiance-general
1

Hi All,

I'm relatively new to Radiance. I'm using the trans modifier and am coming across issues when rendering.

When I try to render my scene for Illuminance values, the output render removes the translucent material from the scene, exposing the interior to the external exterior. However when I render for luminance results, everything works fine.

Has anyone come across this issue before and know what might be causing the issue.

Thanks

Garry

2

Hi Garry,

This is probably one for the FAQ. The "-i" option to rpict has special behavior for glass and trans surfaces, which are normally used to represent transparent materials. I decided it was not very useful to visualize irradiance (or illuminance) on such surfaces, so my hack has rays just go right through them, allowing you to see whatever is on the other side. This is not what everyone expects, however.

Rob Guglielmetti has this post showing the workaround if you really want to get irradiance on all of the first-intersected surfaces:

  http://www.rumblestrip.org/2003/03/19/rendering-falsecolor-on-glass-with-vwrays/

Cheers,
-Greg

···

From: Garry Luu <[email protected]>
Subject: [Radiance-general] Trans Rendering Issue
Date: September 17, 2015 7:07:05 PM PDT

Hi All,

I’m relatively new to Radiance. I’m using the trans modifier and am coming across issues when rendering.

When I try to render my scene for Illuminance values, the output render removes the translucent material from the scene, exposing the interior to the external exterior. However when I render for luminance results, everything works fine.

Has anyone come across this issue before and know what might be causing the issue.

Thanks

Garry

3

Garry,

I think this is its standard mode of operation. Rendering illuminance really only makes sense in a pseudocolor type image (or perhaps one that is contoured). A black and white surface that are side by side would have the same illuminance, so they would be rendered the same. Determining the illuminance onto the emitting side of a trans surface doesn't really have much meaning (and I believe it is non-reflective), so the material is not shown (see the -i option on the rpict manpage).

For accurate visualization, luminance renderings should be selected (which is what our eye or a camera sees).

Rick

···

From: Garry Luu [mailto:[email protected]]
Sent: Thursday, September 17, 2015 10:07 PM
To: [email protected]
Subject: [Radiance-general] Trans Rendering Issue

Hi All,

I'm relatively new to Radiance. I'm using the trans modifier and am coming across issues when rendering.

When I try to render my scene for Illuminance values, the output render removes the translucent material from the scene, exposing the interior to the external exterior. However when I render for luminance results, everything works fine.

Has anyone come across this issue before and know what might be causing the issue.

Thanks

Garry