Basic Lighting Questions


I’m strugling with a few seemingly easy lighting questions. I feel that I’m going in circles trying to solve them and I’m hoping someone in the forums may give some advice…

The basic setup:

  • I have a box (a basement) without any lights inside.
  • Outside of the box (above ground) there’s a Moveable Directional Light (the sun) and a number of Static Lights.
  • In between the lights and the box, there’s a surface facing the lights (the ground).
  • The sun is far away, but the Static Lights are close to the ground

Now my box (that should be completely dark) looks like this:

So there’s a lot of bleeding going on… and a big part of the bleeding seems to come from the bottom (but there’s no light there). How are lights that are on the other side of the surface causing the box to be lit on the inside? (all lights have source radius and lenght 0)

What’s even stranger though, is that if I move the view to be perpendicular to the angle of the sun, the sun starts to be visible through the wall, like so:

So just to be clear: I did not change anything between the first and second screenshot, I just moved my mouse slightly to the left…

What may be causing this? How is the drawing of a Moveable light connected to the viewing angle?

Thanks for any help you might be able to give!

Hahahah… i was in your shoes anout 34 days ago. Now my rooms are clean. Its practice and reading. But i think your issue is you lightmap resolution. Put at least 256. And put the render quality to ptoduction. Make site your uvw are npt overlapping.

Thanks Syrom for your help.

Lightmap resolution doesn’t make a difference… I’ll run at production quality over night to see if that makes a change.

The thing that freaks me out is this change with the viewing angle… it doesn’t make any sense to me! (also: since the sun is a Moveable Directional Light, building quality and lightmap resolution shouldn’t have any effect, right?).


This is what i learned. Keep your wall lightmaps above 256. And make sure you uvw on the 2nd channel flat. And set to production. Also… make sure yoir walls have a ljttle thickness to them. If you follow those simple rules, iy comes out clean. Also… break up EVERY wall. Each face should be its own. I learned that the hard way of trial and error. Once I broke up every wall individualy, the render came ouy WAY cleaner. Also… start small to learn the softwarr. Start by doing a simple cube room with 1 window amd 1 door entrance. Have all the walls be i dividual meshes. Including the ceiling and floor… each its own mesh. Give it a little thickness… like 6 inches and more. It does not have to be 6 inches, it just has to have a little thickness. Then apply a128 to 256 lightmap resolution to all of them. Apply a wooden texture to the floor mesh. Set up a skylight, directional light amd i shet u not… by doing this you will see the workflow easier. I started by importing a apartment unit… and it was hell with light leaks.

Heres another tip. Select the faces of each wall on the inside of the room in your 3d program and detach them as a clone. Add a shell modifier or anything to extrude the surface out just a little to make it into a kinda like slab layer. Then you have better control with all the walls and light leaks.

Yes, the lightmaps resolution have a huge inpact on even production mode. Some ppl use 1048 for walls, i use 512.

Just as a reminder if you plan on using the scalability settings bumping up the resolution may not work on all settings. Creating a mesh with lightmapping in mind, with custom lightmap UV’s is the most consistent way.