Overlapping UV's - Impossible to change UV channel.

Blazyx · March 5, 2015, 8:40am

Hello,

I’ve already looked Erorr : Object has wrapping UVs - Rendering - Unreal Engine Forums and A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums but nothing works

I have a problem with multiple objects of Military Pack Part 1 on Market Place, they have 2 UV channels (channel 0 and channel 1), but when I try to change channel (Light Map Coordinate Index) nothing happens, it stays on channel 0.

If you have a solution, I’m interested

PS : I’m french so there may be errors of translation.

anonymous_user_2ed5b4c7 · March 5, 2015, 9:58am

Hi!
I think you not right undestend how this work.

From this doc

Lightmap Coordinates Index

By default, the first set of UVs (index 0) of a Static Mesh will be used when generating lightmaps for static lighting. This means the same set of coordinates that is used for applying materials to the mesh will also be used for lightmaps. This is quite often not ideal. One reason for this is that the UVs used for generating lightmaps need to be unique, meaning that each face of the mesh must not overlap any other face within the UV space.

The reason for this should be fairly obvious: if the faces share the same UV space, the portion of the lightmap corresponding to that space will be applied to both the faces. This can be great for diffuse and other textures as it allows the texture resolution to be higher for each face. It will result in inaccurate lighting, however. Static Meshes have a property called LightmapCoordinateIndex that allows a specific set of UVs to be used for lightmap generation. By setting this property to point to a set of UVs that are unique and properly set up for lightmaps, Static Meshes can enjoy the best of both worlds: better texture resolution for diffuse textures and accurate lighting from lightmaps.

Tim_Hobson · March 5, 2015, 2:05pm

Hi Blazyx,

There are some issues currently with the Lightmap UVs for the Military Pack 1. I’ve already discussed this with the Content Team and they are going to be taking a look at this very soon to see what needs to be done to improve that.

Some of the meshes are very complex, especially the vehicle ones, and will not properly unwrap using the generate UVs option due to how they were unwrapped.

For the main reason you posted with not being able to set the lightmap coordinate index to anything other than 0. This is the result of having multiple LODs for a mesh. The lightmap coordinate index is setting the lightmap for all LODs to the same channel. If you have not generated a Lightmap for the additional LODs it will not let you set the Lightmap Coordinate Index and will revert to 0 as a default.

This was something I did not mention in the Wiki guide, but since you’ve pointed it out I’ll go back and update that as soon as I have some free time.

If you’re still having issues, please let me know and I can assist.

Blazyx · March 5, 2015, 3:05pm

I sent two messages to the content team but they have not answered me and I don’t know if they are trying to correct the problem or if I should find a way to get a refund for a pack that is not working properly…

Blazyx · April 3, 2015, 12:44pm

Hello,

The Military Pack still does not work (Lightmap UVs). I sent two messages to the content team but they have not answered me and I don’t know if they are trying to correct the problem or if I should find a way to get a refund for a pack that is not working properly, but i don’t know how to do that…

anonymous_user_d523f86b · April 13, 2015, 11:21am

I have the same issue with Military Pack 1. It is unusable (map wont build because of Overlapping UVs) in its basic state and requires a good time wasted on editing the UVs.
Though this pack could be very usefull, i might be requesting for a refund too.

here are the errors i get