I want to add ''kind of'' realistic looking water to my program, so I thought I would make some simple water and add the cool complicated stuff when I get this running normaly. So the water I want to implement right now could be like this: no refractions, fresnel & stuff, just reflections and waves. To make it simpler for now - just reflect the skybox not the actual geometry in the scene, and also have the water as one big quad - since I dont want to change the Y coords of the actual mesh, atlweast for now. So I thought I could do something like this each frame: 1) Use Perlin noise or something to generate the water heightmap. 2) Calcualte normals from that map and store them in a normalmap. 3) Bind the normal map to an OpenGL texture. 4) Calculate the quad where my views frustum intersects with the water plane. 5) Draw the water with a Cg pixel shader whose pseudo-code would be something like this: a) Normal=getNormalFromNormalmap(NoiseMap,Position*noisescalefactor); b) TexCoords=reflect(EyeVector,Normal); c) Color=getCubeMapColor(SkyCube,TexCoords); What I''ve got now is steps 4 & 5 (I use a normalmap created in a paint program). So I have a couple of questions: Should I use Perlin noise or is there something better (runs faster when implemented) for the height map? Or can I somehow generate the normalmap without creating the heightmap? And how can I update (bind) the normal map fast each frame (calling gluBuild2DMipMap... every frame doesnt sound very fast to me ) And also if I have to use Perlin noise, how can I make the noise be ''tiling'' or ''repeating'', and also how can I do perlin noise generation so the noise is ''a bit modified'' noise from the previous frame, not a completely new noise each frame?

I''m not sure what you mean by:

Perlin noise can be optimized to run fairly quickly. Theres a number of "fake" Perlin noise algos out there. I dont have a link or anything but you could try a search. Really though, your noise could be generated at load time, so it may not be an issue anyways.

How can I pre-calculate the water heightmap and have an animated water? Generate a few maps and then interpolate between them or something? And how fast can a perlin noise be? I tried to rip some code from one and got a 5 octave 256*256 map in 0.13 sec (on a P4 2.5 Ghz) - slow to say the least, but how fast can you possibly get it?

Perhaps you could go with one static "perlin-noise-map" and manipulate the texture matrices each fram and animate them in some fancy way?

Good luck


--Spencer

"All in accordance with the profecy..."

Any ideas for the "fancy way" ? All I''ve tried result in that the water becomes wave-less at times and there is always some kind of unnatural-repeating wave pattern.

Could someone just point me in the direction to keep working on? What good water implementations have you done/seen? Should I do per frame height/normal map calculations? Precalculate them for a series of frames? Precalcualte for like every 0.2 or something seconds and interpolate?

[edited by - Bouga on May 8, 2004 4:21:19 PM]

Thanks, I''ll see what I can do with some precalculated height maps and some interpolation.