Hello,
I’m trying to make a large map with a road system. The whole map uses World Partition, roads are made on splines. I noticed that short sections of road disappear when the cells are unloaded, while long sections remain visible, which significantly affects the fps. Is there any way to hide these splines or do I have to make them shorter? In the attached pictures we have 4 splines. They are all separate. Number 4 appears only when I load cells, the rest remains visible even when the cells are unloaded.
-
splines are usually in persistent and used for moving NPCs or even players.
Since they don’t come with a mesh they have no rendering costs… -
landscape splines will only cull when the landscape is culled. They also have no mesh…
-
splines contained within the level which have a mesh, are subject to fustrum culling.
“Long” segments are 1 segment, thefore if you have even 1% of the mesh on screen, the whole segment will be rendered.
This is unavoidable. Splines shouldn’t be used with meshes on a world scale / for roads anyway.
In a modern street like setting you set the spline on landacape to cut the road, use the landacape spline to sculp the landscape.
Move the landscape spline (copy points) to a spline to be thrown into persistent for movement.
Then you create a spline processor (bluetolity) to distribute components of an HISMC along the spline wherever possible.
Any turn should be it’s own spline portion with whatever curved items are required (road mesh? Guardrail?)
Their cost will be neglegible, just like the cost of adding a cube mesh. And they will only be visible when in proximity.
Additionally - and what the Epic team was probably thinking - you can toss the mesh into the RTV for terrain and output it into the landscape texture. This does have its drawbacks, but being into a texture makes the performance cost much lower.
So, in summary.
Im not really sure what you did or how you set up your splines, but even world wide splines have no effect on performance unless they render something (which they should not).
Thanks for reply!
Im not really sure too 
I have 0 SM on scene, only BP for sky, 0 loaded cells from world partition and 5 long splines (they’re still visible). When my camera spots splines on the screen, my fps goes dramatically low but when i press “G” and hide splines, everything is ok. I’m sending two pictures. The first one shows a spline, fps 30-35. As you can see, the terrain is not loaded and the spline is still visible. On the second I hid the tools and the grid and fps increased to 70+.
In Editor the spline itself also has a rendering cost.
Since it’s displayed.
This may actually not affect the end product. You need to test a distribution build to know…
Still, you should figure out where the splines are located and why they are the way they are…
To make splines disappear in the world partition, you need to set the “MaxDrawDistance” parameter on the spline segments. This way, landscape rendering can adjust to follow the splines.