volumetric light rays


i tried to get volumetric light rays through an material with alpha channel, but it doesn’t seem to work. A plane object with holes inside of it (e.g. halostep.blend on 2.42 examples) works, but why don’t the rays shine through an MAT with alpha channel? You can see the light trough the plane, but there are no rays generated.

Is Blender so weak or am i? :rolleyes:

You could try a spot lamp with volumetric halo turned on.

it is turned on - i get the volumetric light and rays if the object has a “hole”. if i use an object without a hole inside of it just with a material with transparency (alpha channel) it doesn’t seem to work.

the rays should shine through the alpha of the material which is placed on the object.

Hmmm… I think that those fake volumetrics on spotlights are based on shadow maps, which means that they won’t recognize alpha maps in textures. Blender will only give you shadows for alpha-mapped objects using the ray option, and as far as I know, the fake volumetrics don’t use rays.

yeah, that last post is completely true. A downside, but Even high end apps(maya, etc.) work the same way…

hmm, doesn’t sound that good…

i used cinema 4d before, was quite easy there, didn’t thought that this is really impossible in blender, but it seems it is… hmmm

anyway, thx for the info.

hmm, well i know its the same in Maya at any rate…

I think i figured it out,
Is this what you are trying to achive?
If so here is the link to the blend file http://www.grq21.com/files/blend2/index.html
Check the setting in the trans material

unfortunately it’s not that i look for…anyway, thx for the work.

here is a picture - a plane with holes inside of it…the rays shine through it. if i put a plane with an alpha (e.g. clouds-texture) in to a normal plane, the rays don’t shine through it.


Fake it. Use Blender’s compositing tools and render layers to your advantage to achieve the wanted look. That’s the only way I can figure out.

Are you saying thet you want the rays to some out of the visable image not around it. So that the light seems to be coming from the visable image area. Is that it, correct me if i am wrong. if so is soming thing like this http://www.grq21.com/ab/index.php?pageID=imgView&imgView=117
i used the Gimp for that, rendered the diff layers then added them, before the nodes were added to blender.
if not ignore

yes, the thing i want to do is a underwater scene. the rays should shine through the water surface. the water exists out of animated textures.


look @ the pic - better as any description :wink:

Take a look at http://www.enricovalenza.com/makebongoenv.html .

thx for the url. i’ll try that out.


the key word in maya is called ray marching:

very nice volumetric caustics: