YOU NEED THE .NET Framework 2.0! here is the link: dotnetfx2.0
1. This shader is NOT a light source, hence there will be no light in your scene with only this shader plugged in a pass-environment input port. So it's visible only in the background and refection/refraction.
2. There is a possibility to create radiance with it: This happens when you have FinalGathering turned on, plugged the shader in the environment port of your pass and when you are sure there is a light in your scene with ZERO intensity!
2.1. If you're crazy enough, you could try to set the light in your scene NOT to 0 and enable its shadows, connect the light's global position through an expression to the sunVector input in your shader and voila: There you have a sun with shadows and the surrounding ambient lightning of your chosen lightning situation.
2.2 This shader can also be used to create a ambient lightning with an ambient occlusion shader like the one that's XSI built in. For this setup, there is no obligation to have a light in your scene. Simply connect the shader in the pass-environment port and plug the ambient occlusion node in your object's material. Turn the "Sampled Environment" output mode on and there you have your radiance from the shader.
- the "Turbidity" parameter controls the "haze" and "dust" amount in the sky and so it specifies the scattering of the light in the atmosphere. The values around 2 to 6 are OK for a clear and sunny day. Above these values the sky get more and more covered and this results in the orange-red coloration.
- the sunSize parameter was used in an older implementation of Fredrik and is obsolete in this one. But i left it there for further use if there is going to be a new release of the shader with this property enabled again.
- the sunVector is the orientation of the sun. It can be connected to a scene light through a vector_share node and an expression (see the example scene in the zip).
- this shader does not produce any shadows(as seen in the example movie) nor does it produce any light except with Final gather turned on. The shadows were created by a point light (as the direct light too) that was connected to the shader (same orientation) by the method stated above.
- you can connect the shader to the environment input of the pass or any material.