I have the project to analyse the influence of using different types of glass on the daylight distribution in a greenhouse.
In this context I thought it would make sense, i.e. give maximum flexibility, to model the glass as a BSDF material (e.g. as can be exported from LBNL Window). I’ve set up a simple test scene: A “Gendaylit” sky, a horizontal glass pane, and somewhat underneath the glass pane an additional horizontal plane on which I compute the light distribution. (Btw I’m using the Blender vi-suite add-on for creating the scene and running the radiance simulation). For test reasons, I first simply took a BSDF for clear glass, i.e. only specular, no diffuse component, i.e. the matrix is diagonal. Now, even with this most trivial BSDF I don’t get a homogeneous distribution of light on my test plane, even when increasing the radiance parameters to seemingly extremely high values.
Why wouldn’t this work? Maybe I lack understanding on how BSDF materials are computed in radiance. I’d be grateful for any advise on this question.
(Ultimately I want to model frosted glass. Would somebody have an advise on how to best model frosted glass? I need physically accurate results. That requires for instance that the diffuse lobe is around the spectral direction and changes with incidence angle.)