Thank you for your reply greg !

Actually I think mixfunc wouldn't fit my needs.

I try to explain what I would like to obtain from another perspective.

I would like to use a specular material representing asphalt (not mirror-like specular material). This will be obtained by trial and errors with metal primitives, using the closer rapresentation, if possible. It will lead surely to a certain error in representation, then, to minimize it, as i will have photometrics values and then BRDF definitions, I would like to use BRDF too.

If I am right, right now, BRDF can just be considered lambertian for the indirect calculation. I would like than to force Radiance to consider them specular (defining specular values by hand).

Is it possible? Is it hard? ANy suggestion for a different approach?

As about using mixfunc, if understood it right, the problem would be that direct calculation would be performed on both brdf and specular, leading me to a quite correct result (due to brdf), but influenced form the specular_bit.

As about the indirect calculation it would be influenced by specular (which is ok) but also from lambertian (indirect calculation of brdf).

Am I wrong?

Lucio

.Hi Lucio,

.

.> I know that I could run two simulations and then combine the

.> results, but it would be much cleaner to be able to use a new kind

.> of primitive able to use BRDF for direct light and a specular

.> material for indirect light. Is it possible to develop such

.> primitive? I'm not very skilled about programming , but I can

.> always learn and help in developing such primitive, if you like. I

.> guess that such kind of primitives could be handy even for other

.> applications. What do you think about it?

.

.Do you want the specular part to be 'pure' -- that is, mirror-like?

.If so, this can be achieved easily enough by specifying a mixfunc

.with a fixed parameter, e.g.:

.

.void metal specular_bit

.0

.0

.5 0.1 0.1 0.1 1 0

.

.void plasdata brdf_data

.{your arguments here}

.

.void mixfunc asphalt

.4 specular_bit brdf_data 0.5 .

.0

.0

.

.Since we are mixing half of each, you need to double each component

.(the specular_bit and the brdf_data), but otherwise this should work.

.

.If, on the other hand, you want a specular component with a soft

.lobe, it gets a little trickier. Essentially, you want to modify

.your BRDF data such that the Gaussian model you are using for the

.specular_bit is taken out. The basic principle still applies, however.

.

.I hope this makes sense.

.-Greg

.

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