Hdri + Fg

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  05 May 2009
Hdri + Fg


I'm having trouble getting accurate lighting from an HDRI in Maya 2009. I have set up the HDRI and I have Raytracing and FG turned on, but the lighting on my object too dark for the environment and I am not getting any shadows at all. Have a look.

I can get better results when I turn on emit light, but then I'm just regulating the light myself. What am I doing wrong? Thanks.
  05 May 2009
Not sure in Maya, but in Max we adjust the rgb value in the map parameters. What kind of HDR options are there ?

TD Animagic Productions
  05 May 2009
It depends on how you set up your shader.

You must:

A) Put it on the incand/ambient color slot of a normal (blinn, lambert, etc) shader
B) Put it on the Out Color of a surface shader
C) Put it on a dedicated IBL Node in the indirect light tab in the render globals (preferred method)

If you placed it anywhere else, including the color (diffuse) of a normal shader, its not going to register as "light".
  05 May 2009
Thanks for the replies.

The above image was rendered with the HDRI attached to an IBL node. The only thing I changed on that node was raising hardware alpha from .5 to 1.
  05 May 2009
From my experience, one way to turn up or down the exposure of the HDRI image based light is to change the hsb "value" attribute of the color gain under the IBL attributes (you can move it below or beyond 1).

try testing it in a simple scene. there may be something wrong with your shader setup on the geometry in the scene for all we know. Create a cube and a sphere, sitting on a plane. texture all with white or gray blinn. Attach your hDRI to the IBL node.
  06 June 2009
Ok, I think I worked out the intensity issue. Thank you for the help.

Will IBL give me sharp shadows though? Right now I am just getting a little bit of shadow in the right direction. Do I need to supplement with software lighting to get accurate shadows?
  06 June 2009
That depends on the GI method you are using and the quality of the HDRI. A popular method is to remove the sun from the HDRI (replace it with a black spot), and then put a directional light at that point for casting light and shadow.
This should take less than a few minutes.
  06 June 2009
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