Performant way to have tons of (fake) volumetric spotlights

Development Rendering
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Hi all. I’m building out a foggy night parking lot environment that we will use for Virtual Production. (img4 for reference on what we’re going for)

In order to capture the morning fog effect ive had to use tons and tons of spotlights that affect the volumetric fog. This is getting too heavy to be run on the VP stage (img1).

I’m looking for an alternative way to fake the volumetric fog effect while still having the possibility of walking around the environment on set (so a simple plane won’t work).
My idea was to use a cone geometry coming from the light, give this a half transparant emissive material with certain falloffs, but this is giving me some issues. (img2) (img3)

The biggest issue is that I don’t know how to make it so the sides have a believeable soft falloff. Currently, I’m using an inverse fresnel curve multiplied to the transparancy. This works a little bit but I don’t have any control over the falloff curve. Within other 3D software I’d be able to plug this into a ramp and perfectly control how this falloff works. Here I can’t find any a way to control this properly.
Then there’s the additional issue that it doesn’t only affect the sides. We see the front of the cone already at an angle. So when the camera moves up or down it makes it more or less transparant.

Is there perhaps a way to have a side falloff to the cone only? Or perhaps a (not too intensive) volumetric material i can use in the cone? Or maybe a full other way to fake this altogether?

Thanks!

IMG1 - Real volumetric spotlights

IMG2 - Transparancy Cone approach

IMG3 - Wireframe of transparant cone approach

IMG4 - Ref of what we’re going for

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i’m curious to see how you solved this! Had to fake this kind of volumetrics lights for a video in similar conditions last summer, we went with the cone mesh and the faded textures, that did the trick but I wonder if there’s any way to optimize the volumetric lights

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Have a look at this sample project. They tackled exactly this.

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late answer but thx a lot!! it did exactly the job
a bit harder to animate though, i wonder if this can be used as a simple mesh and not a dmx fixture, but it worked!

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Yes absolutely.

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