So i was messing around with volumetrics nods and discovered that with cycles it takes ages to render smoke driven by a noise texture or an image texture. But ive tweaked it so that you can get artistically good results much faster. Its a bit of a hack or fake but its still real. using textures that you can find online of clouds, dust or fog simply load them into the shader node in this file and hit render to get a result fast. The number of volume steps is at 100 because it makes virtually zero difference in image quality, and the number of samples is only 125 because it also makes virtually no difference going higher.
Load up my file and give it a good HDRI. Then start go find some images of smoke to try loading into the cube that is the volumetric material. If its too dense then you can lower the density/transparency, and i also have a color node there to change the smoke color. I made the texture drive the emission a bit as well but you dont have to.
Notice i had Depth of Field on you can turn it off if you want. Notice im using OIDN denoise nodes on every layer including volumes, and im using dispersion so expect a bit of blur.
Works in Alpha 2.90 by the way and with viewport optix if you have CUDA.
Some more ideas are rain or snow! and combine with the real-snow addon thats built into Blender. The results are fast and awesome. loaded snow texture, scaled it up a bit to get smaller flakes and voila.
You can also try adding a color ramp after the texture to get more tweaking… You could also mix the whole thing with a 3D blender noise node and put that into the density but that will kill your render times.
Another idea is under water effect… you can add a surface shader to your volume cube change it to glass/transmission and give it an IOR of 1.33 then load an underwater texture ie blue with bubbles and the result is amazing.
The results looking as expected for a texture into the volume shader.You can fake dust and some subtle effects even more efficient, with images as planes with transparency, and if wanted into a emission shader.
I have looked at your blend file.You have set the volume bounces to 500.that is overkill.depending on your task you usally dont need more than 5 .I have read that in the testrender of a open vdb cloud rendering someone rendered with 50 bounces.
I am not sure about your step size of 100.this would skip all details in a volume.
Anyway nice tests.I think that you can tweak the settings even more.
For sure my light bounces are very high. And could be optimized. I forgot to mention that… As for the volume steps, if i was doing the usual smoke sims i would have kept it at 1.00 but in these tests with this sort of hacked way of doing things, having it at 1.00 only serves to dramatically increase the render times… very odd.
