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so i have this little car scene here:

enter image description here

and just to prove that my volume shader "works" i rendered it out in blue.

Here is my result with black (nothing else than color changed):

enter image description here

Now, if i change the blue to black, it won't render in black, so looks like i have a basic beginner problem here and i don't understand the volume shader. What am i doing wrong?

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  • $\begingroup$ What have you tried so far? When I'm looking at both images, the smoke seems to be very thin if it's still very transparent at a density of 2. Is the black color still invisible if you set it to 50? 100? $\endgroup$ Aug 1, 2022 at 12:51
  • $\begingroup$ you are right, with higher density the black color appears but then my smoke looks really bad :( $\endgroup$
    – Chris
    Aug 1, 2022 at 12:52
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    $\begingroup$ Well, black doesn't reflect as much light as white, so the problem is the black seems to disappear inbetween the bright smoke. What you would need is thick black smoke and thin white smoke combined. So maybe you can get a better example when (instead of using a general density setting of 2) you use inverted black and white values as multiplier. But without the exact same smoke simulation I can hardly give you any advice how to achieve the best result. $\endgroup$ Aug 1, 2022 at 12:56
  • $\begingroup$ @GordonBrinkmann: but thanks for your suggestion, i got an idea: i try to increase density just for black parts $\endgroup$
    – Chris
    Aug 1, 2022 at 12:56
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    $\begingroup$ Just my thought exactly ;) $\endgroup$ Aug 1, 2022 at 12:56

1 Answer 1

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Black doesn't reflect as much light as white, so the problem is the black seems to disappear inbetween the bright smoke, especially when the smoke isn't very thick and not absorbing so much light.

To try to fix this or at least get a workaround, you would need thick black smoke and thin white smoke combined. To achieve this - instead of using a general density setting of 2 - you use inverted black and white values as multiplier. And since the Color Ramp mainly outputs values between 0 and 1, you might want to add a Math > Multiply node afterwards to further increase the density.

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