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Saving Lighmap UV space by removing hidden Polygons?

I have a question about open geometry. Currently I am building rooms with cube like geometry. Means closed topology. To save UV space for Lightmass baking I thought I would just delete the Polygons that are not vissible. For example when I put a Wall element on the floor the lower Polygons of the wall are not vissible. Is that a good way to build rooms? Or is there disadvantages if you have open geometry like this?

No, this is actually the usual way.
Nothing wrong with that.

Thanks for your answer. Good to know that. I have thought maybe there is reasons why in most tutorials I saw they worked with Closed Cubes.

Sometimes lights can leak through 1 sided geometry. Deleting a few triangles isn’t going to improve performance, you can instead shrink the UVs for any hidden area to be tiny or just take up unused space.

Yes, that was my thought as well. But if I have perfectly snapped geometry this should not happen right?

Ideally, it should not leak if it is snapped. But there is sometimes quirks to light map baking in UE4.

Most of the time you can delete faces that aren’t visible, but in some cases they are needed to block lighting on other areas. But you can do like ZacD said and reduce their size in the lightmap UV’s so that they don’t waste space since they don’t need detail.

Yes you’re correct. If you get light bleeding from single sided walls, ceilings, floors, etc.- I tend to use BSP outside the player view to block light when working with single sided mesh faces, etc.