[Richard]

Ok I think I've got it!

I place a grid over the HDRI in PS and position the yellow dot at the location of the main light source, export the grid and dot image. Also save this in the same file location as my HDRI for future use.

Bring this pre-mapped sphere into my model and reload the map with the newly created map! Rptate the sphere to position the dot where I want my sun angle and then read off the offset values at the red indicator!

I have a line from the origin to the top of the shere that will cast a shadow so the dot can be rotated on the horizontal plane to opposite the shadow cast, then from my ground plane draw a line from the end of my shadow cast to the top of this line, move it from the end of the shadow cast to the origin and then rotate the sphere on the verical plane until the line interects the centre of the dot!

This way I can use the sun in SU to determine the shadow cast from the HDRI!!!!!

SUPER!!!

Without testing this I think it will work, though I need to ask the experts if this is the right way around doing the grid? How should the numbers run? Where should they start?

Tom, Ron, Anyone????

[RonB]

Hi Richard....I am no expert at this stuff but if this works for you then good, that's all that matters.

You said you downloaded the HDRI Kit....in the kit there is a template that you can overlay onto your HDRI image map and it will give you the exact off set values for the HDRI's light source. I use those values to place an emitter in the scene rather than the sun for shadows....but maybe that can help you.

There has to be an easier way to figure this out....I'll wait for the real experts to chime in.

Ron