UV Performance question

Community Community & Industry Discussion
1

Hello,

Not sure if this should go in General Discussion or Content Creation :expressionless:

Anyway quick question, what is best for performance in this scenario exporting objects out from 3DS Max to UE4 -
If you have 20 objects is it better to treat them as individuals with their own UVs and export them as separate objects into UE4
or have them grouped and have all 20 objects on the same UV (with spacing and no overlapping etc) ?

Thank you kindly

2

If they are all the same object then the first scenario will save memory because it will only keep one in memory and use that for all of the copies. In the second case you would save on draw calls, which is the processing that’s done on each object, but since it’s all of the objects together you use more memory that way.
If they’re all unique, then the second case would be better since you would be using the same amount of memory either way. The downside though is that if one of the objects isn’t visible on screen then it wouldn’t be able to hide it. Also, you could have lightmap issues since you can only use one lightmap for an object so if you merge too many things together then that can increase the surface area and require a large lightmap.

3

Final answer: It depends.

4

Cheers thanks for the prompt response :slight_smile:

5

Oh one other thing I’ve been wondering.
Is performance affected if in the UV creation you just flatten say a box without welding/stitching the sides together?
I guess having gaps between sides does it create more of an issue with UE4?
(see pictures)
Cheers

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6

UV seams do create an extra vertex at each seam. Also hard edges create extra vertices, but if they both are in the same spot, it only creates 1 extra vertex for both of them.

  • To avoid artifacts, you must split your uvs where you use hard edges.

  • You do not however, NEED to use hard edges wherever you split your uvs

7

The only thing as far as UV’s go that affect performance is if you have additional UV channels, since that’s more data.

8

Oh I see thank you very much.
Would you recommend creating a second channel UV in 3ds max or letting UE4 create it on import?
(sorry for all the questions) :slight_smile:

9

Make one by hand in 3ds Max, all of the automatic methods do a poor job