- Thu Jul 14, 2005 12:28 am
#45836
Look at this post in the vray foum, by Vlado (creator of vray):
"To a very large extent, VRay is physically accurate (it has physically accurate GI, materials and lights), and can compute the major components of the rendering equation. For all its physical accuracy, there are effects that Maxwell cannot compute - at all. The raytracing theory states that these affects cannot be computed with an exact (unbiased) raytracing algorithm, no matter what you do.
A simple example: a physical simulation of a light source with reflector (similar to IES lights). Almost all of the "direct" light in the scene comes from caustics. The image below is rendered in VRay. It is biased in the sense that caustics are blurred (although somewhat noisy); however the intensity is correct and they are visible in the mirror. If you render the same scene with Maxwell, the caustics will be perfectly accurate (still noisy though), but they will not appear in the mirror - at all. This may or may not be important in most scenes, but is a limitation that you cannot go around without "fakes" of one sort or another (for example, the IES lights in 3dsmax, which have the caustics pattern precomputed and approximated). This is not limited to mirrors only - the caustics will not be visible through glass either. "
and look this image ,10 minutes of processing:
the same image, 3 hours, and the reflection of caustics appeared (although pretty dim):
Is it physically accurate? or the NL guys did some trick to fake this kind of caustic reflections?
"To a very large extent, VRay is physically accurate (it has physically accurate GI, materials and lights), and can compute the major components of the rendering equation. For all its physical accuracy, there are effects that Maxwell cannot compute - at all. The raytracing theory states that these affects cannot be computed with an exact (unbiased) raytracing algorithm, no matter what you do.
A simple example: a physical simulation of a light source with reflector (similar to IES lights). Almost all of the "direct" light in the scene comes from caustics. The image below is rendered in VRay. It is biased in the sense that caustics are blurred (although somewhat noisy); however the intensity is correct and they are visible in the mirror. If you render the same scene with Maxwell, the caustics will be perfectly accurate (still noisy though), but they will not appear in the mirror - at all. This may or may not be important in most scenes, but is a limitation that you cannot go around without "fakes" of one sort or another (for example, the IES lights in 3dsmax, which have the caustics pattern precomputed and approximated). This is not limited to mirrors only - the caustics will not be visible through glass either. "
and look this image ,10 minutes of processing:
the same image, 3 hours, and the reflection of caustics appeared (although pretty dim):
Is it physically accurate? or the NL guys did some trick to fake this kind of caustic reflections?
Best regards
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- By hwolfejr
- By choo-chee