#Radiosity
Mike
(or anyone else interested),
I wanted to revisit the subject of a `Molecular Blurring Attribute' again,
because I think this is one thing that could dramatically improve the quality
of renderings in Imagine. Mind you, I'm not looking for `true radiosity' (if
there is such a thing on computers). Instead, I think you might be able to
nicely FAKE radiosity by simply blurring ray-traced reflections at the object's
surface.
What radiosity means to me is simply that objects pick-up diffuse or ambient
color from other things around them. Reflections get you halfway there because
they also pick up color from surrounding objects. But Imagine's Ray-traced
reflections are currently much too sharp to simulate radiosity. All objects in
nature (except black holes) reflect light, but their reflections are not sharp
because, even though they may feel smooth to the touch, they actually have tiny
molecule-sized bumps that bounce light back in many different directions,
instead of in a uniform direction like a mirror.
I think you could simulate this effect of diffusely reflected light without any
complicated ray-casting, by merely applying a blurring algorithm to Ray-traced
reflections. I sort of envision it as a slider allowing the user to adjust
anywhere between razor sharp reflections (what you have now), to EXTREMELY
blurry reflections. This might aid in the realism of metals as well.
I have had some success in simulating this false radiosity with global
reflection maps. I take the images into an Image Processor, reduce them down in
size to, say, 50 pixels square, and then blur the heck out of them. Then I add
just a smidgeon of reflectivity to the object, usually in the form of a dark
Brush map. And render it in Scanline. The shaded areas of the object positively
come alive!
But it doesn't work perfectly because the reflections still look more detailed
in areas where there is sharp curvature in the object's surface. Furthermore,
this approach does not work with Traces because object's internal reflections,
and reflections off other objects are still razor sharp, and don't mix with the
blurry global map. And, since the technique only works in Scanline, I either
have to do without shadows, or use some fancy alpha compositing to put them
back in.
The Molecular Blurring parameter is the best thing I can think of to create the
illusion of diffuse light bouncing off a surface. I think you would be amazed
at how much more realistic renderings would look if you put such a feature in.
Perhaps this is something that could be simulated with textures. I kind of
doubt it though. My experiments with algorithmic bumps were pretty
unsuccessful. They came out looking very different depending on the resolution
of the renderings, and overall, quite grainy.
Any thoughts?
-Tim
P.S. Thanks for your explanation of the Altitude seam problem. It helps to know
more about this stuff.