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Creating static shadow-maps at runtime. Possible?

Many objects in my game are static, and so their shadows casting doesnt need to update every frame.
However, my game is procedurally generated, so i cant prebake lighting - shadow maps would need to be made at runtime.
Does anyone have any ideas how/if this could be done in ue4?

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Shadow map compilation takes forever – you really don’t want to do this.
Modern games use dynamic lighting/shadowing, and even ray tracing – what’s the reason you can’t do this?
Add distance fields to your proecedural items and it’ll probably work well!

If anything…
OP needs to consider the fact that the performance gain you get from “static” light baking is only there because of the compilation time that producing it takes out of the final equation.

If the goal is to have a dynamic environment and reduce the performance cost, the answer can’t be “bake lighting” because that performance cost will still have to exist one way (distributed across all frames - dynamic) or another (precomputed at level load).

The process doesn’t have to take “forever” btw. A low cost “on load” adaptation could be made taking around 2m to load a level up.
So you really want your players to wait 2 minutes to load in though?

for procedurally generated levels (generated at the level’s loading time) I don’t see much against having static light baking as an option (which would also happen at that same loading time). it would be a tradeoff of longer loading times to get more runtime performance.

While CPU Lightmass is slow, nowadays GPU Lightmass would be an option (you’d need a raytracing GPU in the game’s system requirements though). back when they announced GPU Lightmass I asked if it would be possible to do baking at runtime but sadly I never got an answer.

I suspect it’s not entirely trivial to implement with all the texture resource assignment and shader upates. It depends how the system was designed, but if the editor can do it seamlessly I don’t think it’s all impossible that they could extend it to happen at runtime

The editor uses its own process for it though.
In a game that you are selling you can’t usually expect your users to have multiple things running at the same time.
Also, I don’t think you can actually package and release swarm as it may be proprietary to epic?

In engine you would basically be doing this with render targets.

You calculate how many you need by splitting up and assigning world driven UV space to each object’s lightmap. You produce each render target of 8k as an atlas. You write the computed shadow to it.
It’s a nightmare just thinking about it XD

And, if you don’t want to have to write functions into all materials to use the RT you also will need to create your own usf or shader file to inject the atlas shadow in… though maybe you can just hook into the existing system for that :thinking:

well swarm is as proprietary to epic as the entire engine. they’re free to include any editor accessories into the runtime as they see fit, it’s their engine after all :smiley:

a mustered solution such as using RTs is indeed a nightmare just to think about it.
also with RTs there would be no texture streaming, they’d all be in memory permanently, and without any texture compression. different lightmaps would mean different material parameters, breaking all instancing entirely.
unless the game is composed of small levels it’s easily gonna eat all the VRAM. it’s a memory problem and not a processing power problem but at that point it’s probably better for performance to just use dynamic lighting

for this to work in a serious manner it needs to be done on the engine side. it would need to save the resulting textures into disk (temporarily, with that game session) so they can be streamed in and out. and it needs to hook into the existing static lighting pipeline.
anything less than that means reinventing the wheel, redoing almost the entire static lighting system, at which point it’s surely not worth the effort

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I think you guys missed my point. What I would like, is simply to have a direction light which does not update it’s depth-map every tick for all objects.

The shadows from the directional light are going to change based on your camera location and everything, so it’s something that does still need to update every tick

I have had some success creating my own custom depth map with a rt+scenecapture. I used that depth map to create shadows in the directional light’s material function.

However, My shadows arent nice and smooth like unreals. they are blocky. My Shadows:


UE4 shadows:

Does anyone know what the maths is to make ue4’s nice soft edged shadows?

Currently mine looks like this:

This thread may help you: How to blur a custom shadow map?. I haven’t done any of this, I just remember reading this thread.

Also, for movable point & spot lights, the shadow maps are automatically cached and reused the next frame using shadow map caching, so you don’t have to worry about those.

thanks, it seems a blur function was recommended in that post you linked. I tried using ue’4s spiral blur function.



It looks better, however now it has a big issue with shadow bias, so its not really useable.

It would be great to know how ue4 does it, As I need my custom shadows to look very similar to ue4’s built in ones.