Light Map Aligned and No Aligned SAME Results


In this image got the same result aligning the lightmap in 3dsmx or without aligning the lightmap in 3dsmax.

What is the correct way?

Unreal 4.6 and 3dsmax 2015.

Hi Marchese,

Unfortunately this isn’t a very good test for something like this.

  1. You have a directional light that is casting on your misaligned and aligned edges. This will wash out any darker or shadowed areas that would have been a problem.

  2. On a single object it may not be as noticeable, especially if you have a higher lightmap resolution which will reduce the how noticeable something like that is.

A better test would be to take your aligned and misaligned ones and doing place them next to each other in a wall formation. Place a skylight in your scene so the shadowed areas are not so dark. On the backside in the shade you will probably see more issues.

You will also notice, even on the aligned one that there are shadowed seams along the edges. These are not a problem of the UV alignment, but instead how light is rendered in lightmass. You can reduce this effect by going in to World Settings > Lightmass > Adjusting the following : Lighting Indirect quality: 2 and Lighting Indirect Smoothness: 0.6. These are good starting places for this and can be tweaked even further to get better results.

If you’re not taken a look, check out World of Level Design and their lightmapping section. it’s all UDK tutorials but they are still relevant:

Another couple of points to remember:

  1. You’re Grid snaps in your UV need to be setup to the target resolution you intend to use in UE4. You can find this grid spacing by taking 1 / [LM resolution] )

  2. Only hard edges need to be snapped to the grid. I wouldn’t worry with something that is more organic in nature or curvy. Only harder edges need worry.

I hope this helps some. :slight_smile:


LightMap in UE4 and 3dsmax


Thanks for helping.

I created a skylight in the scene.

In 3dsmax …

In 3dsmax created 2 uvs, aligned and not aligned.

The grid 3ds max set to 1/256 (EU lightmap) = 0.0039.

7 pixel between the islands

In the EU 4

256 lightmap

9 box on each wall

Result: Very similar.

Conclusion: What is wrong?

It was supposed to wall not aligned showed errors in lightmap?

Aligning the lightmap clusters will improve efficiency of lightmap but not aligned lightmaps does not lead any errors.
You cant align UV of complex shapes anyway.
You have to align 1/254 cuz pixels are taken for edge padding.

Hi Marchese,

I’ve merged your two threads. Please don’t duplicate posts in the future.

Thank you!


Continuing studies …

Possibly I have a lightmap problem in the corners.

1 - The question is: why only in the corners when the rest of the scene this perfect?

2 - I have a scene with strong GI. Where to set the GI?

3 - Snapping Celing and Wall is correct? Snap all objects in cene when possible?