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Hi,
(This post in not off topic, yet *might* contain spoilers, very small ones,
so I'm going to put in some blank space)
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I went to see "The Mummy" last night (good film btw, lots of fun, very like
an Indy Jones film), and I have to say I thought that the graphics were very
very good. Throughout the film, we see lots of computer generated dust
storms, sand formations, rocket trails, and other various vapour/cloud
effects. After the film was over and I had turned my brain back on, I tried
to work out how they did these specific effects.
There were times I thought when the sandstorms looked very like Povray's
media feature ( like the part where the biplane is being chased by a wall of
dust that has the priest's face in it. One of the characters starts shooting
at the dust, and I thought the little explosions in the dust looked very
media-esque). However, most of the other dust/cloud effects looked of much
higher quality than I personally have ever seen Povray accomplish.
Then I remembered seeing a webpage a year or two ago that gave examples of a
method of rendering clouds using things called voxels. These voxels not only
let you have realistic cloud shapes, but let them be shaded by light
sources, and be misty and insubstantial, so you could fly through them. The
cloud examples on the page were very impressive. Unfortunately, I have no
idea of the address of that page.
I did a hunt on the web last night for pages on voxels, and I cam across an
interesting one at
http://www.uni-koblenz.de/fb4/publikationen/gelbereihe/GelbeReihe.bib . On
this page, there is an abstract on a paper that reads :
"In this report we present a volume rendering technique
embedded into a customary ray tracing scheme which is able
to visualize arbitrary particle densities perceived as
realistic clouds of different types found in nature.
Moreover, this technique can be abused to visualize
phenomena like fire, steam, haze, dust or other gaseous
effects in the atmosphere. Our volume rendering strategy
utilizes the volume sampling method, i.e. it computes an
image by successively sampling voxels along the current ray
and it progressively adds the voxel's optical contribution
to the final picture in accordance to the physical laws of
scattering and absorption."
This got me wondering exactly how close in Povray's media engine to a voxel
engine? Those last two terms, "scattering" and "absorption" are already part
of Povray's media implementation. Is Povray's media a voxel engine? If it
isn't, would it be more useful and powerful if it was a voxel engine? As far
as I can make out, voxels give you much greater control over the shape of
your voxel container, and seem to give very smooth and accurate results.
If you want to see some examples of what voxels can do, take a look at
http://www.newtek.com/products/lightwave/hv2/hv2.html . This is a Voxel
plugin for Lightwave 3D (please don't kill me! I know it's a scanline
renderer, but it was the only visual example of voxels I could find), and I
think you will see how powerful voxels can be.
So in summary, my questions are:
1) Is Povray's media engine a voxel based engine?
2) If it is, then how come the images on the Lightwave 3D page look much
cleaner and more realistic than I have ever seen Povray do?
3) If Povray's media engine isn't a voxel based engine, what would be the
benefits of converting it to one (ie, do voxels have any benefits over the
current media implementation)?
4) Would it be difficult to implement this in a raytracer, or specifically
in Povray?
Thanks,
Equiprawn
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Wherever you go, there you are - Buckaroo Banzai
http://m3.easyspace.com/equiprawn/
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