LPV, emissive and me.

Skalbe
Sun, 22 Oct 2017 11:20:31 +0000
Rendering

Hi!

I’m trying to push the lighting to the max in my scene and am experimenting with how far it can go with zero baking. All dynamic all the time.

As far as I understand LPV is a feature that creates approximated voxel volumes from the dynamic ambient lighting data.

As far as I understand, we can use emissive materials to inject colour into said ambient lighting data.

As far as I understand this is the only way to achieve emissive materials ‘lighting’ the scene from dynamic objects.

Otherwise the only way for emissive materials to give light to anything is to bake the data and being static.
Feel free to correct me if I’m wrong. Just my train of thought.

I’m having problems making my emissive work with LPV. I went through similar questions already, as well as:
https://forums.unrealengine.com/development-discussion/rendering/6116-light-propagation-volume-now-works-with-emissive-material?6914-Light-Propagation-Volume-now-works-with-Emissive-Material=

and

docs.unrealengine.com

Light Propagation Volumes

System for dynamically generating global illumination.

At one point I had some kind of a result where a really huge emissive sphere with everything cranked up to max did colour in some voxels in the visualizer, but they were square and very localized and looked like a mask, and looked nowhere near like this in the scene, for example:

Unreal Engine Forums – 23 May 16

LPV Emissive Injection Distance

I don’t know if this is a bug or working as intended, but emissive lighting from LPVs only appears when the emissive material has a certain amount of screen space. If the object is too small or the camera too far away, the LPV injection is disabled...

I did also set the bounds of my emissive mesh to 10.0.
And I did set the r.LightPropagationVolume=1 variable in the console config.

Here is my setup.

The world:

The directional light:

The material:

The post process volume:

And the scene:

As can be seen, everything is marked as movable. It colours in a bit of gold and red from the gold and copper materials as they are reflective so it bleeds in some ambient - makes sense. This all tells me that the LPV system is on and working, yet there is no effect on actual lighting in the scene.The scale of my scene is also very default, no huge distances or anything like that.

The mesh in question, really, is the half pipe on the left side in the scene picture. It has the material from the screenshot on it and it has zero effect on the lighting and I can’t understand why.

Upd.: The red and yellow light volumes in the LPV visualizer are both from reflective materials and the white is from directional light. I can confirm that none of my emissive materials contribute to it at all.

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