// Author: Aleksandr Albert
// Website: www.routter.co.tt

// Description: A deep water ocean shader set
// based on an implementation of a Tessendorf Waves
// originally presented by David Li ( www.david.li/waves )

// The general method is to apply shaders to simulation Framebuffers
// and then sample these framebuffers when rendering the ocean mesh

// The set uses 7 shaders:

// -- Simulation shaders
// [1] ocean_sim_vertex         -> Vertex shader used to set up a 2x2 simulation plane centered at (0,0)
// [2] ocean_subtransform       -> Fragment shader used to subtransform the mesh (generates the displacement map)
// [3] ocean_initial_spectrum   -> Fragment shader used to set intitial wave frequency at a texel coordinate
// [4] ocean_phase              -> Fragment shader used to set wave phase at a texel coordinate
// [5] ocean_spectrum           -> Fragment shader used to set current wave frequency at a texel coordinate
// [6] ocean_normal             -> Fragment shader used to set face normals at a texel coordinate

// -- Rendering Shader
// [7] ocean_main               -> Vertex and Fragment shader used to create the final render


THREE.ShaderLib[ 'ocean_sim_vertex' ] = {
	vertexShader: [
		'varying vec2 vUV;',

		'void main (void) {',
			'vUV = position.xy * 0.5 + 0.5;',
			'gl_Position = vec4(position, 1.0 );',
		'}'
	].join( '\n' )
};
THREE.ShaderLib[ 'ocean_subtransform' ] = {
	uniforms: {
		"u_input": { value: null },
		"u_transformSize": { value: 512.0 },
		"u_subtransformSize": { value: 250.0 }
	},
	fragmentShader: [
		//GPU FFT using a Stockham formulation

		'precision highp float;',
		'#include <common>',

		'uniform sampler2D u_input;',
		'uniform float u_transformSize;',
		'uniform float u_subtransformSize;',

		'varying vec2 vUV;',

		'vec2 multiplyComplex (vec2 a, vec2 b) {',
			'return vec2(a[0] * b[0] - a[1] * b[1], a[1] * b[0] + a[0] * b[1]);',
		'}',

		'void main (void) {',
			'#ifdef HORIZONTAL',
			'float index = vUV.x * u_transformSize - 0.5;',
			'#else',
			'float index = vUV.y * u_transformSize - 0.5;',
			'#endif',

			'float evenIndex = floor(index / u_subtransformSize) * (u_subtransformSize * 0.5) + mod(index, u_subtransformSize * 0.5);',

			//transform two complex sequences simultaneously
			'#ifdef HORIZONTAL',
			'vec4 even = texture2D(u_input, vec2(evenIndex + 0.5, gl_FragCoord.y) / u_transformSize).rgba;',
			'vec4 odd = texture2D(u_input, vec2(evenIndex + u_transformSize * 0.5 + 0.5, gl_FragCoord.y) / u_transformSize).rgba;',
			'#else',
			'vec4 even = texture2D(u_input, vec2(gl_FragCoord.x, evenIndex + 0.5) / u_transformSize).rgba;',
			'vec4 odd = texture2D(u_input, vec2(gl_FragCoord.x, evenIndex + u_transformSize * 0.5 + 0.5) / u_transformSize).rgba;',
			'#endif',

			'float twiddleArgument = -2.0 * PI * (index / u_subtransformSize);',
			'vec2 twiddle = vec2(cos(twiddleArgument), sin(twiddleArgument));',

			'vec2 outputA = even.xy + multiplyComplex(twiddle, odd.xy);',
			'vec2 outputB = even.zw + multiplyComplex(twiddle, odd.zw);',

			'gl_FragColor = vec4(outputA, outputB);',
		'}'
	].join( '\n' )
};
THREE.ShaderLib[ 'ocean_initial_spectrum' ] = {
	uniforms: {
		"u_wind": { value: new THREE.Vector2( 10.0, 10.0 ) },
		"u_resolution": { value: 512.0 },
		"u_size": { value: 250.0 }
	},
	fragmentShader: [
		'precision highp float;',
		'#include <common>',

		'const float G = 9.81;',
		'const float KM = 370.0;',
		'const float CM = 0.23;',

		'uniform vec2 u_wind;',
		'uniform float u_resolution;',
		'uniform float u_size;',

		'float omega (float k) {',
			'return sqrt(G * k * (1.0 + pow2(k / KM)));',
		'}',

		'float tanh (float x) {',
			'return (1.0 - exp(-2.0 * x)) / (1.0 + exp(-2.0 * x));',
		'}',

		'void main (void) {',
			'vec2 coordinates = gl_FragCoord.xy - 0.5;',

			'float n = (coordinates.x < u_resolution * 0.5) ? coordinates.x : coordinates.x - u_resolution;',
			'float m = (coordinates.y < u_resolution * 0.5) ? coordinates.y : coordinates.y - u_resolution;',

			'vec2 K = (2.0 * PI * vec2(n, m)) / u_size;',
			'float k = length(K);',

			'float l_wind = length(u_wind);',

			'float Omega = 0.84;',
			'float kp = G * pow2(Omega / l_wind);',

			'float c = omega(k) / k;',
			'float cp = omega(kp) / kp;',

			'float Lpm = exp(-1.25 * pow2(kp / k));',
			'float gamma = 1.7;',
			'float sigma = 0.08 * (1.0 + 4.0 * pow(Omega, -3.0));',
			'float Gamma = exp(-pow2(sqrt(k / kp) - 1.0) / 2.0 * pow2(sigma));',
			'float Jp = pow(gamma, Gamma);',
			'float Fp = Lpm * Jp * exp(-Omega / sqrt(10.0) * (sqrt(k / kp) - 1.0));',
			'float alphap = 0.006 * sqrt(Omega);',
			'float Bl = 0.5 * alphap * cp / c * Fp;',

			'float z0 = 0.000037 * pow2(l_wind) / G * pow(l_wind / cp, 0.9);',
			'float uStar = 0.41 * l_wind / log(10.0 / z0);',
			'float alpham = 0.01 * ((uStar < CM) ? (1.0 + log(uStar / CM)) : (1.0 + 3.0 * log(uStar / CM)));',
			'float Fm = exp(-0.25 * pow2(k / KM - 1.0));',
			'float Bh = 0.5 * alpham * CM / c * Fm * Lpm;',

			'float a0 = log(2.0) / 4.0;',
			'float am = 0.13 * uStar / CM;',
			'float Delta = tanh(a0 + 4.0 * pow(c / cp, 2.5) + am * pow(CM / c, 2.5));',

			'float cosPhi = dot(normalize(u_wind), normalize(K));',

			'float S = (1.0 / (2.0 * PI)) * pow(k, -4.0) * (Bl + Bh) * (1.0 + Delta * (2.0 * cosPhi * cosPhi - 1.0));',

			'float dk = 2.0 * PI / u_size;',
			'float h = sqrt(S / 2.0) * dk;',

			'if (K.x == 0.0 && K.y == 0.0) {',
				'h = 0.0;', //no DC term
			'}',
			'gl_FragColor = vec4(h, 0.0, 0.0, 0.0);',
		'}'
	].join( '\n' )
};
THREE.ShaderLib[ 'ocean_phase' ] = {
	uniforms: {
		"u_phases": { value: null },
		"u_deltaTime": { value: null },
		"u_resolution": { value: null },
		"u_size": { value: null }
	},
	fragmentShader: [
		'precision highp float;',
		'#include <common>',

		'const float G = 9.81;',
		'const float KM = 370.0;',

		'varying vec2 vUV;',

		'uniform sampler2D u_phases;',
		'uniform float u_deltaTime;',
		'uniform float u_resolution;',
		'uniform float u_size;',

		'float omega (float k) {',
			'return sqrt(G * k * (1.0 + k * k / KM * KM));',
		'}',

		'void main (void) {',
			'float deltaTime = 1.0 / 60.0;',
			'vec2 coordinates = gl_FragCoord.xy - 0.5;',
			'float n = (coordinates.x < u_resolution * 0.5) ? coordinates.x : coordinates.x - u_resolution;',
			'float m = (coordinates.y < u_resolution * 0.5) ? coordinates.y : coordinates.y - u_resolution;',
			'vec2 waveVector = (2.0 * PI * vec2(n, m)) / u_size;',

			'float phase = texture2D(u_phases, vUV).r;',
			'float deltaPhase = omega(length(waveVector)) * u_deltaTime;',
			'phase = mod(phase + deltaPhase, 2.0 * PI);',

			'gl_FragColor = vec4(phase, 0.0, 0.0, 0.0);',
		'}'
	].join( '\n' )
};
THREE.ShaderLib[ 'ocean_spectrum' ] = {
	uniforms: {
		"u_size": { value: null },
		"u_resolution": { value: null },
		"u_choppiness": { value: null },
		"u_phases": { value: null },
		"u_initialSpectrum": { value: null }
	},
	fragmentShader: [
		'precision highp float;',
		'#include <common>',

		'const float G = 9.81;',
		'const float KM = 370.0;',

		'varying vec2 vUV;',

		'uniform float u_size;',
		'uniform float u_resolution;',
		'uniform float u_choppiness;',
		'uniform sampler2D u_phases;',
		'uniform sampler2D u_initialSpectrum;',

		'vec2 multiplyComplex (vec2 a, vec2 b) {',
			'return vec2(a[0] * b[0] - a[1] * b[1], a[1] * b[0] + a[0] * b[1]);',
		'}',

		'vec2 multiplyByI (vec2 z) {',
			'return vec2(-z[1], z[0]);',
		'}',

		'float omega (float k) {',
			'return sqrt(G * k * (1.0 + k * k / KM * KM));',
		'}',

		'void main (void) {',
			'vec2 coordinates = gl_FragCoord.xy - 0.5;',
			'float n = (coordinates.x < u_resolution * 0.5) ? coordinates.x : coordinates.x - u_resolution;',
			'float m = (coordinates.y < u_resolution * 0.5) ? coordinates.y : coordinates.y - u_resolution;',
			'vec2 waveVector = (2.0 * PI * vec2(n, m)) / u_size;',

			'float phase = texture2D(u_phases, vUV).r;',
			'vec2 phaseVector = vec2(cos(phase), sin(phase));',

			'vec2 h0 = texture2D(u_initialSpectrum, vUV).rg;',
			'vec2 h0Star = texture2D(u_initialSpectrum, vec2(1.0 - vUV + 1.0 / u_resolution)).rg;',
			'h0Star.y *= -1.0;',

			'vec2 h = multiplyComplex(h0, phaseVector) + multiplyComplex(h0Star, vec2(phaseVector.x, -phaseVector.y));',

			'vec2 hX = -multiplyByI(h * (waveVector.x / length(waveVector))) * u_choppiness;',
			'vec2 hZ = -multiplyByI(h * (waveVector.y / length(waveVector))) * u_choppiness;',

			//no DC term
			'if (waveVector.x == 0.0 && waveVector.y == 0.0) {',
				'h = vec2(0.0);',
				'hX = vec2(0.0);',
				'hZ = vec2(0.0);',
			'}',

			'gl_FragColor = vec4(hX + multiplyByI(h), hZ);',
		'}'
	].join( '\n' )
};
THREE.ShaderLib[ 'ocean_normals' ] = {
	uniforms: {
		"u_displacementMap": { value: null },
		"u_resolution": { value: null },
		"u_size": { value: null }
	},
	fragmentShader: [
		'precision highp float;',

		'varying vec2 vUV;',

		'uniform sampler2D u_displacementMap;',
		'uniform float u_resolution;',
		'uniform float u_size;',

		'void main (void) {',
			'float texel = 1.0 / u_resolution;',
			'float texelSize = u_size / u_resolution;',

			'vec3 center = texture2D(u_displacementMap, vUV).rgb;',
			'vec3 right = vec3(texelSize, 0.0, 0.0) + texture2D(u_displacementMap, vUV + vec2(texel, 0.0)).rgb - center;',
			'vec3 left = vec3(-texelSize, 0.0, 0.0) + texture2D(u_displacementMap, vUV + vec2(-texel, 0.0)).rgb - center;',
			'vec3 top = vec3(0.0, 0.0, -texelSize) + texture2D(u_displacementMap, vUV + vec2(0.0, -texel)).rgb - center;',
			'vec3 bottom = vec3(0.0, 0.0, texelSize) + texture2D(u_displacementMap, vUV + vec2(0.0, texel)).rgb - center;',

			'vec3 topRight = cross(right, top);',
			'vec3 topLeft = cross(top, left);',
			'vec3 bottomLeft = cross(left, bottom);',
			'vec3 bottomRight = cross(bottom, right);',

			'gl_FragColor = vec4(normalize(topRight + topLeft + bottomLeft + bottomRight), 1.0);',
		'}'
	].join( '\n' )
};
THREE.ShaderLib[ 'ocean_main' ] = {
	uniforms: {
		"u_displacementMap": { value: null },
		"u_normalMap": { value: null },
		"u_geometrySize": { value: null },
		"u_size": { value: null },
		"u_projectionMatrix": { value: null },
		"u_viewMatrix": { value: null },
		"u_cameraPosition": { value: null },
		"u_skyColor": { value: null },
		"u_oceanColor": { value: null },
		"u_sunDirection": { value: null },
		"u_exposure": { value: null }
	},
	vertexShader: [
		'precision highp float;',

		'varying vec3 vPos;',
		'varying vec2 vUV;',

		'uniform mat4 u_projectionMatrix;',
		'uniform mat4 u_viewMatrix;',
		'uniform float u_size;',
		'uniform float u_geometrySize;',
		'uniform sampler2D u_displacementMap;',

		'void main (void) {',
			'vec3 newPos = position + texture2D(u_displacementMap, uv).rgb * (u_geometrySize / u_size);',
			'vPos = newPos;',
			'vUV = uv;',
			'gl_Position = u_projectionMatrix * u_viewMatrix * vec4(newPos, 1.0);',
		'}'
	].join( '\n' ),
	fragmentShader: [
		'precision highp float;',

		'varying vec3 vPos;',
		'varying vec2 vUV;',

		'uniform sampler2D u_displacementMap;',
		'uniform sampler2D u_normalMap;',
		'uniform vec3 u_cameraPosition;',
		'uniform vec3 u_oceanColor;',
		'uniform vec3 u_skyColor;',
		'uniform vec3 u_sunDirection;',
		'uniform float u_exposure;',

		'vec3 hdr (vec3 color, float exposure) {',
			'return 1.0 - exp(-color * exposure);',
		'}',

		'void main (void) {',
			'vec3 normal = texture2D(u_normalMap, vUV).rgb;',

			'vec3 view = normalize(u_cameraPosition - vPos);',
			'float fresnel = 0.02 + 0.98 * pow(1.0 - dot(normal, view), 5.0);',
			'vec3 sky = fresnel * u_skyColor;',

			'float diffuse = clamp(dot(normal, normalize(u_sunDirection)), 0.0, 1.0);',
			'vec3 water = (1.0 - fresnel) * u_oceanColor * u_skyColor * diffuse;',

			'vec3 color = sky + water;',

			'gl_FragColor = vec4(hdr(color, u_exposure), 1.0);',
		'}'
	].join( '\n' )
};