Directional albedo via BRDF/BSDF

radiance-general
1

HI all.

Am doing raytracing in an environment dominated by the reflections from, mostly grass covered, ground.

I’ve been trying to read up on BRDF/BSDF simulation of albedo. I’ve found many sources on a global scale, i.e. for working with data from satellites but am struggling to find something I can use in my radiance simulation.

Any tips on this?

2

Welcome to the forum. I was hoping someone might respond who knows about landscape albedo behavior than I do…

If you don’t know anything more than the overall reflectance of your grassland, you could just use that with a diffuse type such as “plastic,” i.e:

void plastic grass_mat
0
0
5 0.05 0.5 0.1 0 0

grass_mat ring ground
0
0
8 0 0 0 0 0 1 0 100

The photopic albedo of this material would be approximately (0.265*R + 0.670*G + 0.065*B) or 0.35475 in the above example. You can adjust the color and albedo to suit your needs.

If you have more information about how light reflects off your grass at different angles, there are various ways to get this into Radiance. You need to explain what you are starting from, though.

Best,
-Greg

3

Hi Greg .

Thanks for answering, and I apologize for my late response.

I’ve gone wandering into other aspects of PV modelling, which is the basis for my question, but I will wander back sometime in the future, and then follow up on this.

My regards,
LittleBuddha.