* Volume colour absorption

Rather than a single absorption value to control how much light is absorbed as it 
travels through a volume, there's now an additional absorption colour. This is 
used to absorb different R/G/B components of light at different amounts. For 
example, if a white light shines on a volume which absorbs green and blue 
components, the volume will appear red.

To make it easier to use, the colour set in the UI is actually the inverse of the 
absorption colour, so the colour you set is the colour that the volume will 
appear as.

Here's an example of how it works:
http://mke3.net/blender/devel/rendering/volumetrics/vol_col_absorption.jpg

And this can be textured too:
http://mke3.net/blender/devel/rendering/volumetrics/vol_absorb_textured.png

Keep in mind, this doesn't use accurate spectral light wavelength mixing (just 
R/G/B channels) so in cases where the absorption colour is fully red green or 
blue, you'll get non-physical results.

Todo: refactor the volume texturing internal interface...

1 files changed, 8 insertions, 4 deletions

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 63f3f88da50..41035b1c373 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -7737,10 +7737,14 @@ static void do_versions(FileData *fd, Library *lib, Main *main)
 		}
 		
 		for(ma=main->mat.first; ma; ma= ma->id.next) {
-			if (ma->vol_shade_stepsize < 0.001f) ma->vol_shade_stepsize = 0.2f;
-			if (ma->vol_stepsize < 0.001f) ma->vol_stepsize = 0.2f;
-			if (ma->vol_absorption < 0.001f) ma->vol_absorption = 1.0f;
-			if (ma->vol_scattering < 0.001f) ma->vol_scattering = 1.0f;
+			/* trigger for non-volumetric file */
+			if (ma->vol_shade_stepsize < 0.0001f) {
+				ma->vol_shade_stepsize = 0.2f;
+				ma->vol_stepsize = 0.2f;
+				ma->vol_absorption = 1.0f;
+				ma->vol_scattering = 1.0f;
+				ma->vol_absorption_col[0] = ma->vol_absorption_col[1] = ma->vol_absorption_col[2] = 0.0f;
+			}
 		}
 	}