# Light Solutions.

A newbie here...
After briefly going through the documentation of Radiance, it appears that
Radiance is foremost a tool to generate images from scene descriptions.

But what I would like to know:
Can Radiance be used to generate a, let's say radiosity solution, for a
scene, outputting not a projected image, but a description of the light
distribution in the scene.

So typically: the collection of polygon faces in the scene with a measure
for the incoming light for that face.
Or alternatively, a light-value per vertex, maybe, or even lightmap
textures?

Adaptive subdivision of faces would be a big bonus.

Or is Radiance simply not intended for this kind of purpose?

Yours Sincerely,

Bram Stolk

···

--
Owner/Director of Game Studio Abraham Stolk Inc.
[email protected]

Hi Bram,

People have done what you're asking using Radiance, but it is neither easy nor straightforward. Radiance utilizes some curved primitives (spheres and cones mostly) that do not have a polygonal equivalent. And while you can generate irradiance values at arbitrary points, which when multiplied by diffuse reflectance and divided by pi give you radiosity, you would have to specify where the points were.

If you start with a list of triangles, you can write a script or program to create a list of points where you want to compute radiosity, but then you need to re-associate the calculated values with the appropriate diffuse reflectances to get radiosity. Generating textures with mappings to polygons is a lot more work, but there are ways to do that as well. Unfortunately, none of it is done for you.

I have a vague memory of Richard Gillibrand working on this problem some 12 years ago or so, but I can't find where he wrote any of it up. Others have worked on it as well, so maybe they can chime in.

Cheers,
-Greg

···

From: Bram Stolk <[email protected]>
Subject: [Radiance-general] Light Solutions.
Date: January 8, 2016 2:38:07 PM PST

A newbie here...
After briefly going through the documentation of Radiance, it appears that Radiance is foremost a tool to generate images from scene descriptions.

But what I would like to know:
Can Radiance be used to generate a, let's say radiosity solution, for a scene, outputting not a projected image, but a description of the light distribution in the scene.

So typically: the collection of polygon faces in the scene with a measure for the incoming light for that face.
Or alternatively, a light-value per vertex, maybe, or even lightmap textures?

Adaptive subdivision of faces would be a big bonus.

Or is Radiance simply not intended for this kind of purpose?

Yours Sincerely,

Bram Stolk

--
Owner/Director of Game Studio Abraham Stolk Inc.
[email protected]

Hi,
Try here for UV:
and same few years after:
with the associated octave script for using:
let me know if you have troubles
G

···

On 9 Jan 2016, at 03:34, Greg Ward <[email protected]> wrote:

Hi Bram,

People have done what you're asking using Radiance, but it is neither easy nor straightforward. Radiance utilizes some curved primitives (spheres and cones mostly) that do not have a polygonal equivalent. And while you can generate irradiance values at arbitrary points, which when multiplied by diffuse reflectance and divided by pi give you radiosity, you would have to specify where the points were.

If you start with a list of triangles, you can write a script or program to create a list of points where you want to compute radiosity, but then you need to re-associate the calculated values with the appropriate diffuse reflectances to get radiosity. Generating textures with mappings to polygons is a lot more work, but there are ways to do that as well. Unfortunately, none of it is done for you.

I have a vague memory of Richard Gillibrand working on this problem some 12 years ago or so, but I can't find where he wrote any of it up. Others have worked on it as well, so maybe they can chime in.

Cheers,
-Greg

From: Bram Stolk <[email protected] <mailto:[email protected]>>
Subject: [Radiance-general] Light Solutions.
Date: January 8, 2016 2:38:07 PM PST

A newbie here...
After briefly going through the documentation of Radiance, it appears that Radiance is foremost a tool to generate images from scene descriptions.

But what I would like to know:
Can Radiance be used to generate a, let's say radiosity solution, for a scene, outputting not a projected image, but a description of the light distribution in the scene.

So typically: the collection of polygon faces in the scene with a measure for the incoming light for that face.
Or alternatively, a light-value per vertex, maybe, or even lightmap textures?

Adaptive subdivision of faces would be a big bonus.

Or is Radiance simply not intended for this kind of purpose?

Yours Sincerely,

Bram Stolk

--
Owner/Director of Game Studio Abraham Stolk Inc.