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drossxyu
08-24-2007, 05:42 AM
Is there a way to light a scene without an HDRI image or Physical Sun/Sky and still get a high dynamic range render? Are the mental ray light shaders capable of doing such a thing? Basically, I'm looking to get reflections in my scene where the actual light source ( ex: a window with an area light in it ) is most prominent and the rest of the scene is only subtley reflected. I'm able to do this with maxwell with a poly plane with a maxwell emitter attached.

-F

sixbysixx
08-24-2007, 01:29 PM
All Mental Ray renders are HDR, 32bit float - you'll only have to change the framebuffer to 32bit float and save the render as an appropriate file format like openEXR...

drossxyu
08-24-2007, 02:15 PM
Right, but how do I know that my light is emitting a value that's beyond 1. I know you can push the specular attribute on a shader beyond 1 so that you receive a 'super-white' highlight, but how does this translate to the light itself? Is anything above an intensity of 1 on a light considered 'HDR' or does it not work that way?

drossxyu
08-24-2007, 04:24 PM
Here's an example of a test scene i'm trying to light. It contains two MR area lights ( converted from maya software area lights) w\ MR physical light shaders in each hole. A MIA material is applied to all of the objects with a reflectivity of .6. My primary framebuffer was set to RGBA )float) 4x32 bit and I batch rendered it out to an .exr. Both of these image are created from the same .exr but with different exposure adjustments. Notice how it's a completely flat exposure change ( almost like the brightness has just been brought down ) , probably due to the fact that there wasn't much dynamic range in my scene to begin with. Is this because my lights should be brighter or there needs to be an adjustment to my material?

sixbysixx
08-24-2007, 04:36 PM
Did you Batch Render them or rendered from the viewport?
If you render 32bit from the viewport you have to switch on Preview Convert Tiles and switch off Preview Tonemap Tiles in the MR Render Settings, only then your tmp files will be proper 32bit (They might look funky in the viewport though...)

drossxyu
08-24-2007, 04:36 PM
Sorry if it seems like i'm thinking out loud here, but I was able to get the super-bright highlights I was looking for by turning the visibility of the area light on. The exposure in the .exr now works the way you would expect ( highlights staying bright as the exposure is lowered ). But is this the only way to get a super bright reflection?

drossxyu
08-24-2007, 04:42 PM
I batch rendered it to an .exr, but being able to save out of the viewport is helpful.

chronic
08-24-2007, 04:57 PM
you can overdrive the incandesance of an object to get super-bright refections, and using final gather you can get an effect smilar to maxwell

rendering in the render window always gives you an 8 bit image, only batch rendering can output a 32 bit image

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