Creating a displacement map for oceans based on Gerstner waves

Graphics and GPU Programming Programming

Started by BloodOrange1981 March 11, 2015 05:09 PM

0 comments, last by Ashaman73 9 years, 1 month ago

BloodOrange1981

389

Author

March 11, 2015 05:09 PM

Hi Everybody. If you're not playing Hotline Miami 2 right now (I will be after posting this!) I would like some help with what might be a simple question.

I'm currently trying to render an ocean scene, as I thought it would be a good practical project to make where I learn new techniques and knowledge along the way. I have been using this article as a reference http://http.developer.nvidia.com/GPUGems/gpugems_ch01.html

I currently have a very basic Gerstner wave "generator" that runs on the cpu side, but can't really play with more than 5 or so waves at the current level of tesselation in a single threaded app without some nasty slowdown.

In the article I linked to there is a method of rendering a displacement/height map in the shader to a render target, a pretty quick way to accumulate 15 or more individual waves' effects in a shader. For each channel (r,g,b) in the map you can store the displacement of each vertex in the x,y and z directions respectively.

Outside of deferred rendering I have little experience of rendering to a render target and reading custom data from the texture - so before I go ahead I wanted to check if normalization of values/packing is really necessary?

I see textures as big buffers of data. So therefore there shouldn't be problems holding arbitrary float values from anything like -34.0f to 500.0f, for example.Loading would be simple too right? Unless there's something about texture samplers I don't know.

However I'd like to visually check the created texture, as that is a pretty simple way to see if everything is ok. Without knowing the max displacement created by summing the sines beforehand how can I normalize values to 0.0f - 1.0f? Do I assume that the max possible displacement is -textureSize/2.0f < d < textureSize/2.0f where 'd' is the displacement?

Thanks

Ashaman73

13,718

March 17, 2015 07:47 AM

I see textures as big buffers of data. So therefore there shouldn't be problems holding arbitrary float values from anything like -34.0f to 500.0f, for example.Loading would be simple too right? Unless there's something about texture samplers I don't know.

Yep, take a 16 bit floating point texture to save some bandwidth.

However I'd like to visually check the created texture, as that is a pretty simple way to see if everything is ok.

Take a look at tone-mapping. It is the same concept, you need to compress one space to a limited space. A very simple tone mapper would be

1-(1/(1+x)) or if you like to scale it 1-(1/(1+s*x)). Putting this into a simple shader:


float wave_height = ...
vec3 color;
if(wave_height<0) {
    // red for negative values
   color = vec3( 1.0 - 1.0/(1.0-wave_height), 0.0,0.0);
} else {
    // green for positive values
   color = vec3( 0.0,1.0 - 1.0/(1.0+wave_height), 0.0);
}

Ashaman

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Creating a displacement map for oceans based on Gerstner waves

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Creating a displacement map for oceans based on Gerstner waves

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