Sampling Volumes from an arbitrary position?

Unity Engine
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1

I was doing a game jam over the weekend. I wanted to make fog roll in as the player got close to an object.

The natural thing to do was to stick a volume on the object that cranks up the fog.

However, this wasn’t quite right: the fog came in if the camera got close to the object. That would be fine for a first-person game, but this one was third-person!

My solution wound up being to call VolumeManager.instance.Update, which takes a Transform to sample the Volume from:

        VolumeManager.instance.Update(GameManager.Instance.player.transform, LayerMask.GetMask("Default"));
        var fog = VolumeManager.instance.stack.GetComponent<FogEffectComponent>();

        if (fog != null)
        {
            fogMaterial.SetFloat("_Fog_Start", fog.fogStart.value);
            fogMaterial.SetFloat("_Fog_End", fog.fogEnd.value);
        }

I use the result to set values on the fog material, which is used in a full screen pass.

I also needed to do this with bloom. Since that’s a built-in effect, I couldn’t just set values on some “bloom material”. My solution to that wound up being to create a global volume that applies bloom, and then to control its weight:

      var playerBloom = VolumeManager.instance.stack.GetComponent<PlayerBloomEffectComponent>();

        globalBloomVolume.weight = playerBloom.intensity.value;

This requires an extra global volume, and it’s just…kind of fiddly.

So, my question: is there an easier way to control where volumes get sampled from? It would be particularly nice if I could this only for some volumes, or only for some volume components.

2

Don’t know if there is such an option but maybe you could set the position of the volume based on the distance (vector) from the player to the camera?

3

In URP/HDRP, that’s what the volume trigger property on the camera does:

8893611--1216260--upload_2023-3-21_21-51-29.png

I have no idea for builtin, sorry… it probably depends on what post-processing stacks you use and stuff.

3 Likes
4

Oh! There it is! Perfect, thank you. I had tried searching stuff like “sample volume from point”, but I hadn’t thought of looking up “trigger” after seeing it…