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Can anyone please tell me what the offset value represent for image based environment mapping.

Take the illumination channel for example!

If I have a map just say 2000 x 1000 pixels - I assume it maps spherically (at a scale factor of 1) - then if I change the offset values are they in degrees, an arbitary value etc?

I have so much trouble locating correctly imaged based environments I've thought of a way it may help me if I bring a sphere into my model mapped with a grid and a sun located on the grid corresponding to the HDRI sun location then rotate the sphere to get the sun located where I would like it and then read the offset values from the sphere corresponding to a set indicator. Then use these values as the offset!

Just trying to take the hit and miss out of HDRI location!

OOPS SORRY - read the manual - 0-100 equates to 0-360 degrees!

Hmmm? I still do have one question though - at a scale of 1 is any sized image still mapped to the sphere only once or is this dependant on the image size?

Richard, yes...the image is mapped to the virtual sphere once. The size of the image has nothing to do with the mapping...it's the scale set at the U and V that determines the wrap. Easy to get a visual of whats going on by placing a fully reflective ball at the Zero point in the scene and do some tests by adjusting the settings of the reflective map to get an idea of whats happening.

Also suggest you download the HDRI Image Kit from the Goodies forum and check it out. There are some things in it that may help you, take a look at the PDF too. It may or may not help....

Cheers, Ron

Thanks Ron - yes mate I had already downloaded and looked through your files though still makes the process difficult!

Just trying to make it much much easier, maybe not as accurate though just simple!