Anyone know why a flame (texture/material defined with media) will show up
perfectly with nothing (black) in the background...but as soon as
I put a wall (plane) behind it...the flame disappears?

I've verified that the object is in front of the wall...but not sure why
the wall makes it disappear.

Post a reply to this message

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Skeety wrote:
| Anyone know why a flame (texture/material defined with media) will
show up
| perfectly with nothing (black) in the background...but as soon as
| I put a wall (plane) behind it...the flame disappears?
|
| I've verified that the object is in front of the wall...but not
sure why
| the wall makes it disappear.
|
	Because your wall is already white and emission media works by
adding the color of the media to whatever is behind. When pov tries
to add the color of the media to the white of the walls it stays white.

	Here's a picture showing this effect:
http://jeberger.free.fr/mpov/emission1.png

	The easiest way to get around this is to use megapov 0.7 which
includes a new type of emission media that fixes the problem. Here's
the result with this patch:
http://jeberger.free.fr/mpov/emission3.png

	Or if you want to stick with official pov, you will have to combine
an absorbing media along with the emission and get this result:
http://jeberger.free.fr/mpov/emission2.png

	The code for these examples is at:
http://jeberger.free.fr/mpov/mpov.html#emission

		Jerome
- --
******************************
*      Jerome M. Berger      *
* mailto:jbe### [at] ifrancecom *
*  http://jeberger.free.fr/  *
******************************
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (GNU/Linux)

iD8DBQFBlkhxqIYJdJhyixIRAqBbAJ9+EsX2zHYIgCHdsk7IIZaahqTfCgCfZIhG
N1A7tnSIWXoA2DImrLLgv3U=
=DA0j
-----END PGP SIGNATURE-----

Post a reply to this message

> The easiest way to get around this is to use megapov 0.7 which
> includes a new type of emission media that fixes the problem. Here's
> the result with this patch:
> http://jeberger.free.fr/mpov/emission3.png
>
> Or if you want to stick with official pov, you will have to combine
> an absorbing media along with the emission and get this result:
> http://jeberger.free.fr/mpov/emission2.png

If it's a flame you're going for though, I wouldn't recommend either of
these solutions since they're physically inaccurate. I would simply try to
darken whatever's behind the flame.

 - Slime
 [ http://www.slimeland.com/ ]

Post a reply to this message

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Slime wrote:
| If it's a flame you're going for though, I wouldn't recommend either of
| these solutions since they're physically inaccurate. I would simply
try to
| darken whatever's behind the flame.
|
	In fact, there is no physically accurate way to model a flame in
POV. A real flame combines some absorption and some emission, but to
model it, you would need to be able to represent the complete
emission and absorption spectra. Since POV represents light as RGB,
it is impossible to model the flame accurately (all the more so since
the Red, Green and Blue spectra used by computers overlap...) That
being the case, I would forget about physical accuracy and look at
what gives the best results from an artistic standpoint.

		Jerome

- --
******************************
*      Jerome M. Berger      *
* mailto:jbe### [at] ifrancecom *
*  http://jeberger.free.fr/  *
******************************
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (GNU/Linux)

iD8DBQFBllj2qIYJdJhyixIRAlFnAKCUFcqKkbovA05hTaGu4lPfQg0UeQCfei9w
MAYvBSt6hNbuOaizpSQ1uPc=
=efvm
-----END PGP SIGNATURE-----

Post a reply to this message