vrayscattervolume, distancetex sampling

[super gnu]

ive no idea if this is a bug, or expected behaviour..

given scattervolume is a volumetric material, and distance tex is a volumetric texture, i would expect (hope) that the distance tex would affect the scattervolume throughout its volume. as it is, it only affects the geometry surface of the scattervolume object.

im back trying to do a planetary atmosphere, and ive mapped the scattervolume radius with a distance tex linked to the earth's surface. the idea is to get the volume to reduce in density the further you are from the surface of the earth. i was not getting the expected result.

see attached screengrab...



I've offset the earth object so it intersects the atmosphere geometry, and set it to non-renderable. you can see the density changing on the surface of the atmosphere geometry, but not within it.

in this scenario i would hope to see the density changing throughout the scattervolume.

can the material be adjusted to sample 3d textures at every point within the volume?

i hope that makes sense.

[hermit.crab]

I'll investigate and write back.

[hermit.crab]

It seems it is a limitation of the VRayScatterVolume, however, it should work out with a VRayEnvironmentFog contained in a Gizmo that has it's density mapped with the VRayDistanceTex.

[super gnu]

hi, i appreciate its a limitation of scattervolume, and i know env fog will work, but

a) env fog is WAY slower to render,
b) it doesnt have the same scattering and sss abilities as scattervolume, (so i cant do even a basic approximation of rayleigh scattering, making it useless for a proper atmosphere) , and
c) scattervolume is specifically a volumetric material, for doing the "insides" of objects, so being able to apply changes to the volume with maps seems a fairly critical ability...

otherwise its only useful for homogenous materials and is missing a huge range of potential uses.

In fact, the map slots only affecting the surface of the object makes zero sense for a volumetric shader- scattervolume is specifically not meant for surface shading.. so i would consider it broken in this state.

When would you ever need to change the density or colour on the surface of a volumetric effect, but not inside? it doesnt even affect the backfaces.

please note this also applies to sss2 shader and "new" vraymaterial translucency.. none of them actually sample maps in 3d despite being "3d" shaders.


can i ask pretty please that something might be done about this? The use cases for a proper volumetric shader with proper texture sampling are incredibly broad.

[hermit.crab]

I've passed your feedback to our developers. We'll consider it and see if we can improve the VRayScatterVolume.