water caustics

local SHADER_CODE = [[
    #include "mta-helper.fx"

    #define TAU 6.28318530718
    #define MAX_ITER 6

    sampler Sampler0 : register( s0 );

    struct VSInput
    {
        float4 Position     : POSITION0;
        float4 Diffuse      : COLOR0;
        float2 TexCoord     : TEXCOORD0;
    };

    struct PSInput
    {
        float4 Position     : POSITION0;
        float2 TexCoord     : TEXCOORD0;
        float4 Diffuse      : COLOR0;
    };

    float3 vec3(float x,float y,float z) { return float3(x,y,z); }
    float3 vec3(float x) { return float3(x,x,x); }
    float3 vec3(float2 x,float y) { return float3(float2(x.x,x.y),y); }

    float2 vec2(float x,float y) { return float2(x,y); }
    float2 vec2(float x) { return float2(x,x); }

    PSInput VertexShaderFunction(VSInput VS)
    {
        PSInput PS = (PSInput)0;

        float4 worldPosition    = mul(VS.Position, gWorld);
        float4 viewPosition     = mul(worldPosition, gView);
        float4 position         = mul(viewPosition, gProjection);

        PS.Position             = position;
        PS.TexCoord             = VS.TexCoord;

        PS.Diffuse              = MTACalcGTABuildingDiffuse(VS.Diffuse);

        return PS;
    }

    float4 PixelShaderFunction( PSInput PS ) : COLOR0
    {
        float time = gTime*0.5+23.0;
        float2 uv = PS.TexCoord.xy / 1;

        float2 p = fmod(uv*TAU*2.0, TAU)-250.0;

        float2 i = vec2(p);
        float c = 1.0;
        float inten = 0.005;

        for (int n = 0; n < MAX_ITER; n++)
        {
            float t = time * (1.0 - (3.5 / float(n+1)));
            i = p + vec2(cos(t - i.x) + sin(t + i.y), sin(t - i.y) + cos(t + i.x));
            c += 1.0/length(vec2(p.x / (sin(i.x+t)/inten),p.y / (cos(i.y+t)/inten)));
        }

        c /= float(MAX_ITER);
        c = 1.17-pow(c, 1.4);

        float3 colour = vec3(pow(abs(c), 8.0));
        colour = clamp(colour + vec3(0.0, 0.35, 0.5), 0.0, 1.0);

        float4 maincolor = tex2D(Sampler0, PS.TexCoord) * PS.Diffuse;
        return float4(colour, 1.0) * maincolor;
    }

    technique
    {
        pass P0
        {
            AlphaBlendEnable = TRUE;
            VertexShader     = compile vs_3_0 VertexShaderFunction();
            PixelShader      = compile ps_3_0 PixelShaderFunction();
        }
    }
]]

local shader = DxShader(SHADER_CODE, 0, 3, true, "world,object")
shader:applyToWorldTexture("*")

addEventHandler('onClientRender', root, function()
    dxDrawImage(300, 300, 300, 300, shader)
end )