Why does vertex painting on a large mesh cause my frame rate to drop?

link textHello,

I thought it would be nice to test the new ue4 out by rebuilding my project that I was making in udk to ue4.
Only when I wanted to start vertex painting the terrain (which is an imported static mesh) I noticed that everything became very laggy, the fps went down from 56~ to 18~ fps and that was only by hovering my mouse above the terrain, when I started to paint the engine froze for about a minute without even seeing what you painted, only when it stopped freezing could you see what you had painted.
I did this a few times until I opened the task manager and saw that ue4 was using 12gb of ram (and I think it could go even higher if I continued painting).

The terrain has about 7000 vertices, but I got the same problem on a mesh that had 3500 vertices, only static meshes with much lower vertex count didn’t have this problem. When I painted the terrain in udk I didn’t have a problem at all.

So my question is is this a bug? Does anyone else have the same problem?

Hi ,

Would you mind posting your dxdiag so we can further assist you with this? Thank you and have a great day!

Hi ,

I’ve added the dxdiag above

Hi ,

So far we have been unable to reproduce this on our end, do you have a test asset you wouldn’t mind sharing so we could see what is going on? Thank you!

Thanks for replying!
I’ve sorta fixed the problem, and sorta not

The terrain that I wanted to vertexpaint had quite a high custom collision mesh, I deleted it and the engine didn’t freeze anymore when I wanted to paint, but I still got some dramatic frame drops when painting (cursor also disappears sometimes when painting)

I’ve put a link to the file beneath(terrain with custom collision), couldn’t attach it cause of the 524kb limit



Thank you for your report. We were not able to investigate this on the engine version you reported, but there have been many version changes to UE4 since this question was first posted. With a new version of the Engine comes new fixes and it is possible that this issue has changed or may no longer occur. Due to timetable of when this issue was first posted, we are marking this post as resolved for tracking purposes.
If you are still experiencing the issue you reported in the current engine version, then please respond to this message with additional information and we will investigate as soon as possible. If you are experiencing a similar, but different issue at this time, please submit a new report for it.

Thank you.

no this problem still lagging when painting in large meshs in ue4.20.1

I’m getting this issue as well.

This sort of happened to me, whenever i was vertex painting a large mesh i’m using for terrain, if i was still in vertex paint mode, and then hit play, fps would be super low, if i went out of vertex paint and in to object selection, then hit play, fps would go back up.

Still lag in 4.21.2

Still happens in 4.22.2

You can try this by creating a 127, 2 section, 12 panel terrain, exporting it out to FBX, importing it as a mesh, and applying any vertex paint material on it - even solid colors.

Resources used on PC don’t seem to matter/affect the lag.

Still happens to me in 4.25.4, cursor is lagging when I paint over any mesh.