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Changing lightmap resolution on box brush has no effect

Hi there,

I am getting slightlz frustrated, as changing the lightmap resolution on the box brush in Unreal editor does not appear to have an effect. I am previewing the scene with “Alt + 0” (Or in the Viewport Lit > Optimization Viewmodes > Lightmap Density) which shows the lightmap density as colors in the viewport. When I select the floor of my room (which was modeled with a box brush) and I increase the lightmap resolution from 64 to 256 nothing changes, the density still appears to be the same. The resolution in the density preview does not change at all. However, when I change the lightmap resolution on regular assets, (or a box this works. So my question is: Can’t the lightmap resolution of a box brush be changed, though the details panels exposes a lightmap resolution parameter? This seems odd.

  • Ruediger

If you’re using BSP then you need to lower the lightmap resolution number–it’s the number of units per pixel, so when you increase it then the lightmap resolution is smaller. For static meshes the resolution number is directly the pixel resolution of the lightmap.

Allright, thanks for the information. Too bad that this is not indicated in any way when previewing the lightmap density. No matter to which value I set it, the lightmap density preview of BSPs does not change which is kind of a bummer, because i think especially people doing archviz will use BSPs to quickly add in some walls or floors. Seeing the appropriate lightmap density would be very helpful.

It might be the case that you have to build lighting before it updates that view

hi and sorry for “necropost” but i think is an important thread and I could not find other discussions about your words. I also noticed that, unlike the static mesh, in which the green color control in lightmap density mode takes place in real time changing the res value, in the geometry brushes it is necessary to go “by trial and error” and verify each time building scene light to find the right compromise. what I’d like to ask to close the discussion is if there is a more immediate way to set the correct values even with bsp without having to convert them first into static mesh

BSP is something from the past. Originally in unreal 1 it was all you had to create level geometry. Then slowly static meshes replaced BSP for multiple reasons. The main reason is “speed” of rendering. It is still in there but if you want to quickly add a wall it is much better to use a box from “Basic” and not BSP. You should never build a lot of geometry with BSP. You will run into problems. Not just performance problems, other things like invisible collision or giant black spots. Just don’t use it if possible and its very possible not to use it :slight_smile:

I wouldn’t put much faith into the lightmap density view, there’s a lot of factors that it can’t take into account that kind of makes it useless. For example, something doesn’t need a high resolution lightmap if it’s not receiving complex shadows.

What it more comes down to is being aware of texture resolutions for your mesh and putting in what you think is acceptable for that mesh. For BSP the resolution is the number of world units per lightmap pixel.

Thanks for this, was looking for an explanation as to why this was but was hard to find.