three.js/examples/js/shaders/ParallaxShader.js

( function () {

	// Parallax Occlusion shaders from
	//		http://sunandblackcat.com/tipFullView.php?topicid=28
	// No tangent-space transforms logic based on
	//	 http://mmikkelsen3d.blogspot.sk/2012/02/parallaxpoc-mapping-and-no-tangent.html
	var ParallaxShader = {
	// Ordered from fastest to best quality.
		modes: {
			none: 'NO_PARALLAX',
			basic: 'USE_BASIC_PARALLAX',
			steep: 'USE_STEEP_PARALLAX',
			occlusion: 'USE_OCLUSION_PARALLAX',
			// a.k.a. POM
			relief: 'USE_RELIEF_PARALLAX'
		},
		uniforms: {
			'bumpMap': {
				value: null
			},
			'map': {
				value: null
			},
			'parallaxScale': {
				value: null
			},
			'parallaxMinLayers': {
				value: null
			},
			'parallaxMaxLayers': {
				value: null
			}
		},
		vertexShader: [ 'varying vec2 vUv;', 'varying vec3 vViewPosition;', 'varying vec3 vNormal;', 'void main() {', '	vUv = uv;', '	vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );', '	vViewPosition = -mvPosition.xyz;', '	vNormal = normalize( normalMatrix * normal );', '	gl_Position = projectionMatrix * mvPosition;', '}' ].join( '\n' ),
		fragmentShader: [ 'uniform sampler2D bumpMap;', 'uniform sampler2D map;', 'uniform float parallaxScale;', 'uniform float parallaxMinLayers;', 'uniform float parallaxMaxLayers;', 'varying vec2 vUv;', 'varying vec3 vViewPosition;', 'varying vec3 vNormal;', '#ifdef USE_BASIC_PARALLAX', '	vec2 parallaxMap( in vec3 V ) {', '		float initialHeight = texture2D( bumpMap, vUv ).r;', // No Offset Limitting: messy, floating output at grazing angles.
			//"vec2 texCoordOffset = parallaxScale * V.xy / V.z * initialHeight;",
			// Offset Limiting
			'		vec2 texCoordOffset = parallaxScale * V.xy * initialHeight;', '		return vUv - texCoordOffset;', '	}', '#else', '	vec2 parallaxMap( in vec3 V ) {', // Determine number of layers from angle between V and N
			'		float numLayers = mix( parallaxMaxLayers, parallaxMinLayers, abs( dot( vec3( 0.0, 0.0, 1.0 ), V ) ) );', '		float layerHeight = 1.0 / numLayers;', '		float currentLayerHeight = 0.0;', // Shift of texture coordinates for each iteration
			'		vec2 dtex = parallaxScale * V.xy / V.z / numLayers;', '		vec2 currentTextureCoords = vUv;', '		float heightFromTexture = texture2D( bumpMap, currentTextureCoords ).r;', // while ( heightFromTexture > currentLayerHeight )
			// Infinite loops are not well supported. Do a "large" finite
			// loop, but not too large, as it slows down some compilers.
			'		for ( int i = 0; i < 30; i += 1 ) {', '			if ( heightFromTexture <= currentLayerHeight ) {', '				break;', '			}', '			currentLayerHeight += layerHeight;', // Shift texture coordinates along vector V
			'			currentTextureCoords -= dtex;', '			heightFromTexture = texture2D( bumpMap, currentTextureCoords ).r;', '		}', '		#ifdef USE_STEEP_PARALLAX', '			return currentTextureCoords;', '		#elif defined( USE_RELIEF_PARALLAX )', '			vec2 deltaTexCoord = dtex / 2.0;', '			float deltaHeight = layerHeight / 2.0;', // Return to the mid point of previous layer
			'			currentTextureCoords += deltaTexCoord;', '			currentLayerHeight -= deltaHeight;', // Binary search to increase precision of Steep Parallax Mapping
			'			const int numSearches = 5;', '			for ( int i = 0; i < numSearches; i += 1 ) {', '				deltaTexCoord /= 2.0;', '				deltaHeight /= 2.0;', '				heightFromTexture = texture2D( bumpMap, currentTextureCoords ).r;', // Shift along or against vector V
			'				if( heightFromTexture > currentLayerHeight ) {', // Below the surface
			'					currentTextureCoords -= deltaTexCoord;', '					currentLayerHeight += deltaHeight;', '				} else {', // above the surface
			'					currentTextureCoords += deltaTexCoord;', '					currentLayerHeight -= deltaHeight;', '				}', '			}', '			return currentTextureCoords;', '		#elif defined( USE_OCLUSION_PARALLAX )', '			vec2 prevTCoords = currentTextureCoords + dtex;', // Heights for linear interpolation
			'			float nextH = heightFromTexture - currentLayerHeight;', '			float prevH = texture2D( bumpMap, prevTCoords ).r - currentLayerHeight + layerHeight;', // Proportions for linear interpolation
			'			float weight = nextH / ( nextH - prevH );', // Interpolation of texture coordinates
			'			return prevTCoords * weight + currentTextureCoords * ( 1.0 - weight );', '		#else', // NO_PARALLAX
			'			return vUv;', '		#endif', '	}', '#endif', 'vec2 perturbUv( vec3 surfPosition, vec3 surfNormal, vec3 viewPosition ) {', '	vec2 texDx = dFdx( vUv );', '	vec2 texDy = dFdy( vUv );', '	vec3 vSigmaX = dFdx( surfPosition );', '	vec3 vSigmaY = dFdy( surfPosition );', '	vec3 vR1 = cross( vSigmaY, surfNormal );', '	vec3 vR2 = cross( surfNormal, vSigmaX );', '	float fDet = dot( vSigmaX, vR1 );', '	vec2 vProjVscr = ( 1.0 / fDet ) * vec2( dot( vR1, viewPosition ), dot( vR2, viewPosition ) );', '	vec3 vProjVtex;', '	vProjVtex.xy = texDx * vProjVscr.x + texDy * vProjVscr.y;', '	vProjVtex.z = dot( surfNormal, viewPosition );', '	return parallaxMap( vProjVtex );', '}', 'void main() {', '	vec2 mapUv = perturbUv( -vViewPosition, normalize( vNormal ), normalize( vViewPosition ) );', '	gl_FragColor = texture2D( map, mapUv );', '}' ].join( '\n' )
	};

	THREE.ParallaxShader = ParallaxShader;

} )();