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I want to do a small patch of mist or smoke, and have lights go through it and light it up, in an animation.

I've seen the mist option directly in the interface, but as far I know it creates mist that doesn't interact with light.

I've seen the volumetric scattering in the compositor, which give great results, but you can only apply it to the entire scene to the best of my knowledge. I want it to be in particular area.

How would you go about that?

Here's an example : enter image description here

http://il5.picdn.net/shutterstock/videos/15120553/thumb/1.jpg

You see the different lights affect the smoke / mist just like in real life, and some of the light goes through it.

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  • $\begingroup$ Could you provide some screenshots/video samples? What renderer you want to use for this? $\endgroup$ – cgslav Apr 12 '17 at 23:24
  • $\begingroup$ I edited my question to add a picture, and I want to use cycle render. $\endgroup$ – Natasha Apr 12 '17 at 23:45
  • $\begingroup$ Do you want static background lights or animated mesh lights flying trough the smoke? $\endgroup$ – cgslav Apr 12 '17 at 23:46
  • $\begingroup$ The lights will move and animate $\endgroup$ – Natasha Apr 12 '17 at 23:50
  • $\begingroup$ Ok, I'll make an answer in couple of minutes with animated mesh lights. $\endgroup$ – cgslav Apr 12 '17 at 23:50
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Final result:

Final

First thoughts:

This is pretty complex setup and very demanding for the hardware. It's made using Cycles. You should have some knowledge in such fields as:

  • creating smoke,
  • setting up materials,
  • render layers,
  • basic compositing.

Final result is made with low settings.

Scene setup:

First of all we need to setup up our scene.

  1. Crank up Volume Light Paths. I've used 4. Higher values gives you better light scattering trough smoke. This step is essential for the whole thing.

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  1. Make Environment color black, or whatever you need in your case.

Object setup:

In my scene I've used two Ngon filled Circles, one for the light, and second for the Smoke Flow. One Empty for Force Field. Cube for Smoke Domain.

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Light:

Small Circle behind Smoke Domain with Emission shader. It could be Sphere or anything else.

This is node setup I've used for it:

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Smoke Flow:

Again it's Circle, and again you can use different object. If you for example want to have really dense smoke, you can use Sphere for it.

Note 1: Remember to turn off view and render of this mesh in Outliner or assign to it Transparent Shader!

Set Temp Diff. really low to keep smoke in place. In this case it's 0.01.

Note 2: Denser smoke will need higher Volume Light Paths and/or smaller smoke material density (we will get to it).

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Smoke Domain:

This is two step process.

1. Smoke Domain setup:

Nothing special here. Only Noise Method is worth mentioning, lower setting will give you smoother smoke.

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2. Smoke Domain material:

This is almost default material after using Quick Smoke, with addition of Brightness/Contrast node, which gives us harder and wither feel. Also default density value is decreased (this is connected to Smoke Flow Note 1 from above).

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Force Field:

To make some smoke movement I've used Force Field > Turbulence. I like to stop smoke flow then move it by a force in such cases. Force field is assigned to an Empty.

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Render Layers and Composite:

To make some light blur and streaks you will need to move light emitter to another layer.

In this case I've moved my light mesh to second layer and kept other object on first layer then made two Render Layers. First Smoke, which is rendering first layer, and second - Light which is rendering second layer.

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After final rendering, go to Composite nodes and make this setup. This is just blurred out light with streaks and gamma correction of smoke and light.

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Final thoughts:

As I said at the beginning, this isn't easy if you're new to Blender. You can find any information related to techniques used here or you can just ask me and I will extend this as needed.

You need to have in mind that values used in this particular setup will vary in any other. Things like density, emission strength, smoke resolution, volume light paths etc. could be much different then these.

Check my blend file. Load it, check it, quick rewrite it.

Blend file:

Edit:

You need to use for this filmic-blender. You should always use it.

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  • $\begingroup$ @Natasha post your result by editing your question and we will see what's wrong. $\endgroup$ – cgslav Apr 24 '17 at 19:12
  • $\begingroup$ Just did, as you can see it's getting there but not there yet. $\endgroup$ – Natasha Apr 24 '17 at 19:21
  • $\begingroup$ @Natasha please upload file to: blend-exchange.giantcowfilms.com it's hard to tell what it could be just from screenshot. $\endgroup$ – cgslav Apr 24 '17 at 19:24
  • $\begingroup$ @Natasha ok, I think I know what's the problem, are you using Filmic Blender for Color Management? If not - you should. I have used it in this case and forget to mention it as it is somewhat must have for any photo realism approach. $\endgroup$ – cgslav Apr 24 '17 at 19:31

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