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View Full Version : Shadows cast from HDR IBL?

sugarandfat
07-17-2006, 04:47 AM
Let's say I had a 3D object composited into a peice of video where the light is dappled sunlight through leaves, and the 3D was to be lit by HDRI from the scene.

How would I get the dappled patterns to be cast onto the object? My light probe is fairly small compared to the object, and was placed in a patch of pure sunlight so as to capture the full light range.

I'm going to play with using the image to displace a sphere, so that the dark tree silouhettes are brought in spacially from the lighter background, then map the HDRI onto the sphere,

but if anyone has a better idea...

Daniel.
mindsample
07-17-2006, 02:20 PM
If you actually "light" the scene with your IBL you could always create shadow-casting geometry to achieve the desired effect.
However - and I am not sure if I am misunderstanding you htere - if you captured the tree when you photographed the environment you would have darker patches showing up on your CG, after all the sunlight/bright areas were partly occluded due to the tree casting the shadow?

Say hi to good old Melbourne from me!
ZippZopp
07-17-2006, 05:49 PM
lots of times the HDRI won't give you really nice shadows, at least the kind you're looking for. you'd need a really detailed high res hdri to get that. i'd suggest using the hdri and then also using a spot light as your primary light, map the color of the light with a texture similar to leaves on a tree to get that dappled light....that would be much more efficient that trying to create shadow casting geometry.
sugarandfat
07-18-2006, 12:04 AM
> if you captured the tree when you photographed the environment you would have darker
> patches showing up on your CG

Yeah, I would still want the shadow geomoetry to be casting the IBL, so that they don't block the light and not cast any of their own.

> using the hdri and then also using a spot light as your primary light, map the color of the
> light with a texture similar to leaves on a tree to get that dappled light....

I thought about that, I could just grab that patch of the image and convert it to an 8 bit file for the light's colour. But how do I then stop it competing with the main light from the HDRI? Paint it out in CS2?
Might not be a bad idea, actually...

Daniel.
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