/*********************************************************************NVMH3****
Copyright NVIDIA Corporation 2003
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*AS IS* AND NVIDIA AND ITS SUPPLIERS DISCLAIM ALL WARRANTIES, EITHER EXPRESS
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AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL NVIDIA OR ITS SUPPLIERS
BE LIABLE FOR ANY SPECIAL, INCIDENTAL, INDIRECT, OR CONSEQUENTIAL DAMAGES
WHATSOEVER (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS PROFITS,
BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR ANY OTHER PECUNIARY LOSS)
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Comments:
	Simple ocean shader with animated bump map and geometric waves
	Based partly on "Effective Water Simulation From Physical Models", GPU Gems

11 Aug 05: converted from HLSL to GLSL by Jeff Doyle (nfz) to work in Ogre

******************************************************************************/


uniform sampler2D NormalMap;
uniform samplerCube EnvironmentMap;
uniform vec4 deepColor;
uniform vec4 shallowColor;
uniform vec4 reflectionColor;
uniform float reflectionAmount;
uniform float reflectionBlur;
uniform float waterAmount;
uniform float fresnelPower;
uniform float fresnelBias;
uniform float hdrMultiplier;

varying mat3 rotMatrix; // first row of the 3x3 transform from tangent to cube space
varying vec2 bumpCoord0;
varying vec2 bumpCoord1;
varying vec2 bumpCoord2;
varying vec3 eyeVector;


void main(void)
{
	// sum normal maps
	// sample from 3 different points so no texture repetition is noticeable
    vec4 t0 = texture2D(NormalMap, bumpCoord0) * 2.0 - 1.0;
    vec4 t1 = texture2D(NormalMap, bumpCoord1) * 2.0 - 1.0;
    vec4 t2 = texture2D(NormalMap, bumpCoord2) * 2.0 - 1.0;
    vec3 N = t0.xyz + t1.xyz + t2.xyz;

    N = normalize(rotMatrix * N);

	// reflection
    vec3 E = normalize(eyeVector);
    vec3 R = reflect(E, N);
    // Ogre conversion for cube map lookup
    R.z = -R.z;

    vec4 reflection = textureCube(EnvironmentMap, R, reflectionBlur);
    // cheap hdr effect
    reflection.rgb *= (reflection.r + reflection.g + reflection.b) * hdrMultiplier;

	// fresnel
    float facing = 1.0 - dot(-E, N);
    float fresnel = clamp(fresnelBias + pow(facing, fresnelPower), 0.0, 1.0);

    vec4 waterColor = mix(shallowColor, deepColor, facing) * waterAmount;

    reflection = mix(waterColor,  reflection * reflectionColor, fresnel) * reflectionAmount;
    gl_FragColor = waterColor + reflection;
}