Lightmap increase brightness of diffuse?

From my understanding by default a lightmap only serves to darken parts of the diffuse texture, as jME will use the white to “pass” the diffuse color, and anything darker will multiply to reduce the brightness of the color. First, is this correct? If that is so, then what’s the right way to make it so that 50% gray is the pass through color, and then anything brighter on the lightmap will lighten the color of the diffuse and anything darker will darken it? Is this possible through the material editor, or do I have do modify the source (like write a shader)?

Actually the correct approach is to add the lightmap as an additional light instead of multiplying diffuse color by the lightmap. Thus in jME3, lightmaps are used as an ambient occlusion map as opposed to a lightmap.

Initially, that confused me a bit, but I understand what you mean now. Because all I have in the scene is an ambient light, my lightmap effectively controls how much indirect (ambient) light parts of the model receive.

By “correct” do you mean “the approach I should take” or “the approach the industry uses for a lightmap”? Because if you mean the former, I’m not sure how to do that. I’m pretty much trying to do what this polycount article says for brightening values in a diffuse map, which involves making 50% gray the pass value.

EDIT: On second thought, what I’m trying to achieve is probably better done via a glow map. I’m going to look into that real quick and report back.

Yeah, so the glow map does what I want much better. Thanks for informing me though. How computationally intensive is the bloom post processing filter? My game is on Android, hence resources are limited. Is doing the bloom downsampling good enough?

I am guessing you’re looking for an emission map? I.e., the emission color is added to the material color but is not affected by the diffuse map.

Yeah, in the material editor the option is “glowmap” so that’s what I called it. I think it’s the same as the emission map.