Water: Fluid Surface; or Static Mesh; or BSP?

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FNG / Fresh Meat
Feb 19, 2008
Sorry -- I don't mean to drown y'all with yet another question about fluids.

Pick your poison, or Different strokes for different folks. I have noticed that different level designers will use different formats for their water surfaces. Some folks use fluid surfaces -- makes sense to me. But others have very effectively used either sheet static meshes or sheet BSPs for their water surfaces. Any of the three can be made to look pretty kewl -- by that I mean if we are talking about game immersion -- excuse the pun -- any of the three methods have been used by RO Level designers to successfully give players the sense that they are looking at something that looks like water.

So why not stick to fluid surfaces? What advantages or disadvantages are there to the three ways of presenting a water surface? Enquiring minds want to know ;o)


FNG / Fresh Meat
Nov 21, 2005
meshes have UV maps, therefore make water flow down the stream and not sideways in a bent :p


FNG / Fresh Meat
May 21, 2006
Fluid info actors are more or less procedural meshes, meaning that they are "animated" meshes. You get the benefit of being able to adjust the movement, frequency, and height of the wave motion. The downsides of Fluid Actors are that they use high-poly construction and the movement uses system resources meaning that your level could take a performance hit if you use too many of them or don't set them up correctly. On the other hand, I think Arad uses 8 to 10 fluid surface actors for the creek that runs through the middle of the map.

With static meshe and BSP sheets, you obviously don't get the same level of control or "realism". You need to use panning textures to simulate current or movement, but it won't be a 3D effect. The big upside to using those is they are very,very low poly and cause a neglible impact to resources.


FNG / Fresh Meat
Nov 22, 2005
  • UV mapping (e.g. for river-bends)
  • complex shapes possible
  • 3d wave movement possible with xProcMesh
  • relatively light on performance (compared to same shape with BSP)
  • lighting is bad unless it has many polys (if it's used for a xProcMesh, many polys are a given though, because of the waves, so it's not much of a problem)
  • work to create and set up
  • if complex: Performance hit. Not scalable by user!
  • 3d wave-movement
  • easy to set up
  • users can scale complexity with PhysicsDetail setting! (From full detail down to just two non-moving triangles!)
  • limited shape
  • impossible or at least difficult to create river-bends
  • seems to randomly stop working... (bug. Just change any setting of the FluidSurface and then change it back before you release your level)
  • easy to set up
  • as long as it's kept simple the shape can be freely chosen
  • as long as it's kept simple the performance is good...
  • lightmap lighting (not often needed on water. For really detailed stuff like shadows of leaves a projector has to be used anyway)
  • no movement possible
  • no complex shapes feasible
  • river-bends possible but load of work...


FNG / Fresh Meat
Feb 17, 2006
Also don't forget XProc meshes, I used them in Dog Green and another map.
thing with them is you can make them fit perfectly to the river, and then UVmap it so the texture flows as it should do.