Sharper shadows using a light probe

radiance-general
1

Hi there

When illuminating a scene, say objects on a table, using a light probe, is there
any way to get sharper, darker shadows (of the objects on the table)? I use the
genbox command for the light map, obviously the light is not as focused because
it's spread out over the large box 100 100 100. If the surface is specular,
nice reflections are rendered but if it is purely diffuse, the shadows hardly
occur.

Thanks

Tarik

···

--
Tarik Rahman
PhD student, Institute of Perception, Action and Behaviour
School of Informatics
University of Edinburgh

2

Tarik Rahman wrote:

Hi there

When illuminating a scene, say objects on a table, using a light probe, is there
any way to get sharper, darker shadows (of the objects on the table)? I use the
genbox command for the light map, obviously the light is not as focused because
it's spread out over the large box 100 100 100. If the surface is specular,
nice reflections are rendered but if it is purely diffuse, the shadows hardly
occur.

I would think that for a light probe, the probe image would be more important than the geometry it's mapped on to. What is your light probe like? Does it have a small source of light, or is it spread over a large area? If your light probe image has a large source of light, or many smaller ones spread out, then the results you describe sound about right.

bye

3

Hi Tarik,

Ian is right about the environment determining the sharpness of your shadows as much as your object geometry. You should also consider using the new mksource program, especially if your environment map contains the sort of small, intense sources that should generate shadows. However, to do so, you'll need to map your light probe onto a distant glow source rather than a large box.

See the postings from last month on mksource, starting with:

     http://www.radiance-online.org/pipermail/radiance-general/2005-April/002602.html

-Greg

···

From: Ian Tester <[email protected]>
Date: May 25, 2005 7:08:56 AM PDT

Tarik Rahman wrote:

Hi there
When illuminating a scene, say objects on a table, using a light probe, is there
any way to get sharper, darker shadows (of the objects on the table)? I use the
genbox command for the light map, obviously the light is not as focused because
it's spread out over the large box 100 100 100. If the surface is specular,
nice reflections are rendered but if it is purely diffuse, the shadows hardly
occur.

I would think that for a light probe, the probe image would be more important than the geometry it's mapped on to. What is your light probe like? Does it have a small source of light, or is it spread over a large area? If your light probe image has a large source of light, or many smaller ones spread out, then the results you describe sound about right.

bye