Dear UE4 team, dear community,

UE4 is for me the most amazing engine in the world - it could be even more amazing, if there were not this really akward Lightmap/UV behavior. But lets be specific:

This is a screenshot of my scene

We all see these horrible lightmaps between two parts of this low-poly-seat.

Now look at the lightmaps:

Meshes are:

  • aligned on the grid in MAYA
  • have 64 px Lightmap resolution - but even 2k resolution does not help, so it’s not about mesh distance in the map.

But that actualy just distracts your from the real matter. Lightmapping workflows ought to be much less complicated, and it sometimes seems there’s no logic behind - random behaviour,

i’ll show you what i mean:

We’re not doing games only but also Apps for the Automotive industry, i.e. we absoluetely need to do use sometimes high-poly meshes like this one:

But look at that! Lighmapping works perfectly on this mesh:

Other high-poly AND low-poly meshes (see above) look like cr*p:


Look Here:

What I want to say:

  • In low poly meshes we try everything to get good lightmaps → we get bad results
  • In high poly meshes we CAN NOT do things like align huge organic mesh to map pixels → … we get bad results

This is a serious problem for us, as we are not able to deliver anything in that quality.

Please give us a solution or at least a hint what to do about that.


  • Its not about lightmap resolution (tried that)
  • Its not about 64 -2 = 62 px padding as suggested in some forums
  • Its not about pixel alignment on the map, as we cant do that for high poly and it happens on aligned maps too

Ok concerning lightmap on low poly meshes, thanks to help from forum:

“uv shells are colliding with borders which is prohibited as well. Add padding to this areas.”

“your UV mapping could be better, you have some surfaces that are separated that don’t need to be, plus a lot of things that are distorted so that they end up as rectangle shapes which is not good either”