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need advice on water vertex shader


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#1 timothyjlaird   Members   -  Reputation: 404

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Posted 30 June 2012 - 01:49 PM

I'm trying to implement some simple water in XNA. Right now I'm focusing on the vertex shader part to generate at least passably realistic wave motion by manipulating the 'y' values of my grid. This is the code I'm using for the shader (time is gameTime.TotalGameTime.Milliseconds / 80)...

float4x4 xWorldViewProjection;
Texture xColoredTexture;
int time;
sampler ColoredTextureSampler = sampler_state
{
texture = <xColoredTexture>;
magfilter = LINEAR;
minfilter = LINEAR;
mipfilter = LINEAR;
AddressU = mirror;
AddressV = mirror;
};
struct VertexIn
{
float4 position : POSITION;
float2 textureCoordinates : TEXCOORD0;
};
struct VertexOut
{
float4 Position : POSITION;
float2 textureCoordinates : TEXCOORD0;
};
VertexOut VertexShaderFunction(VertexIn input)
{
	VertexOut Output = (VertexOut)0;
float sinarg = mul(input.position.x, 0.5) + time;
input.position.y = mul(0.5, sin(sinarg));
Output.Position = mul(input.position, xWorldViewProjection);
Output.textureCoordinates = input.textureCoordinates;
return Output;
}
float4 PixelShaderFunction(VertexOut input) : COLOR0
{
float4 color;
float4 maskcolor;
color = tex2D(ColoredTextureSampler, input.textureCoordinates.xy);
	return color;
}
technique Textured
{
	pass Pass0
	{
		VertexShader = compile vs_2_0 VertexShaderFunction();
		PixelShader = compile ps_2_0 PixelShaderFunction();
	}
}

The problem is that sin waves only get me so far. Can someone point me in the direction of a better algorithm to calculate the y values for my verticies in my vertex shader? Preferably something that isn't too math heavy?

Short video of where I am right now:

http://www.youtube.com/watch?v=cJDf0xZbpow

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#2 Jason Z   Crossbones+   -  Reputation: 4905

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Posted 01 July 2012 - 05:36 AM

You can grab my WaterSimulation demo from my Hieroglyph 3 engine here. It uses a navier stokes style solver to implement the water animation, and it currently runs in the compute shader. That won't work directly in XNA, but you could always move the solver portion to the CPU and just upload the height data to the GPU. Or you could modify it to run in the vertex shader using multiple passes - it all depends on what you are looking for.

If you have any questions about the implementation just let me know.

#3 timothyjlaird   Members   -  Reputation: 404

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Posted 01 July 2012 - 06:13 AM

You can grab my WaterSimulation demo from my Hieroglyph 3 engine here. It uses a navier stokes style solver to implement the water animation, and it currently runs in the compute shader. That won't work directly in XNA, but you could always move the solver portion to the CPU and just upload the height data to the GPU. Or you could modify it to run in the vertex shader using multiple passes - it all depends on what you are looking for.

If you have any questions about the implementation just let me know.

Thanks! This will take me a while to figure out but I appreciate the help.




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