RectAreaLight: Updated to new LTC model

examples/webgl_lights_rectarealight.html

@@ -61,7 +61,7 @@
 			var origin = new THREE.Object3D();
 
 			var matStdParams = {
-				roughness: 0.044676705160855, // calculated from shininess = 1000
+				roughness: 0.0,
 				metalness: 0.0
 			};
 
@@ -78,7 +78,7 @@
 			var mshStdSphere = new THREE.Mesh( geoSphere, matStdObjects );
 			var mshStdKnot = new THREE.Mesh( geoKnot, matStdObjects );
 
-			var amb = new THREE.AmbientLight( 0xffffff, 0.0 );
+			var amb = new THREE.AmbientLight( 0xffffff, 0.1 );
 
 			var rectLight;
 			var rectLightHelper;
@@ -125,7 +125,7 @@
 
 				camera.position.set( 0, 20, 35 );
 
-				rectLight = new THREE.RectAreaLight( 0xffffff, 500, 10, 10 );
+				rectLight = new THREE.RectAreaLight( 0xffffff, 200, 10, 10 );
 				rectLight.position.set( 5, 5, 0 );
 
 				// TODO: ensure RectAreaLight handles target param correctly
@@ -185,10 +185,11 @@
 				if ( param.motion ) {
 
 					update();
-					rectLightHelper.update();
 
 				}
 
+				rectLightHelper.update();
+
 				renderer.render( scene, camera );
 
 				stats.update();
@@ -197,7 +198,7 @@
 
 			function update() {
 
-				var t = ( Date.now() / 1000 );
+				var t = ( Date.now() / 2000 );
 
 				// move light in circle around center
 				// change light height with sine curve
@@ -263,13 +264,13 @@
 
 				} );
 
-				lightFolder.add( param, 'intensity', 0.0, 1000 ).onChange( function ( val ) {
+				lightFolder.add( param, 'intensity', 0.0, 400 ).onChange( function ( val ) {
 
 					rectLight.intensity = val;
 
 				} );
 
-				lightFolder.add( param, 'ambient', 0.0, 1 ).step( 0.01 ).onChange( function ( val ) {
+				lightFolder.add( param, 'ambient', 0.0, 0.2 ).step( 0.01 ).onChange( function ( val ) {
 
 					amb.intensity = val;
 

src/renderers/WebGLRenderer.js

@@ -1896,11 +1896,10 @@ function WebGLRenderer( parameters ) {
 			// RectAreaLight Texture
 			// TODO (mrdoob): Find a nicer implementation
 
-			if ( m_uniforms.ltcMat !== undefined ) m_uniforms.ltcMat.value = UniformsLib.LTC_MAT_TEXTURE;
-			if ( m_uniforms.ltcMag !== undefined ) m_uniforms.ltcMag.value = UniformsLib.LTC_MAG_TEXTURE;
+			if ( m_uniforms.ltc_1 !== undefined ) m_uniforms.ltc_1.value = UniformsLib.LTC_1;
+			if ( m_uniforms.ltc_2 !== undefined ) m_uniforms.ltc_2.value = UniformsLib.LTC_2;
 
-			WebGLUniforms.upload(
-				_gl, materialProperties.uniformsList, m_uniforms, _this );
+			WebGLUniforms.upload( _gl, materialProperties.uniformsList, m_uniforms, _this );
 
 		}
 

src/renderers/shaders/ShaderChunk/bsdfs.glsl

@@ -112,12 +112,9 @@ vec3 BRDF_Specular_GGX( const in IncidentLight incidentLight, const in Geometric
 
 // Rect Area Light
 
-// Area light computation code adapted from:
 // Real-Time Polygonal-Light Shading with Linearly Transformed Cosines
-// By: Eric Heitz, Jonathan Dupuy, Stephen Hill and David Neubelt
-// https://drive.google.com/file/d/0BzvWIdpUpRx_d09ndGVjNVJzZjA/view
-// https://eheitzresearch.wordpress.com/415-2/
-// http://blog.selfshadow.com/sandbox/ltc.html
+// by Eric Heitz, Jonathan Dupuy, Stephen Hill and David Neubelt
+// code: https://github.com/selfshadow/ltc_code/
 
 vec2 LTC_Uv( const in vec3 N, const in vec3 V, const in float roughness ) {
 
@@ -125,51 +122,40 @@ vec2 LTC_Uv( const in vec3 N, const in vec3 V, const in float roughness ) {
 	const float LUT_SCALE = ( LUT_SIZE - 1.0 ) / LUT_SIZE;
 	const float LUT_BIAS  = 0.5 / LUT_SIZE;
 
-	float theta = acos( dot( N, V ) );
+	float dotNV = saturate( dot( N, V ) );
 
-	// Parameterization of texture:
-	// sqrt(roughness) -> [0,1]
-	// theta -> [0, PI/2]
-	vec2 uv = vec2(
-		sqrt( saturate( roughness ) ),
-		saturate( theta / ( 0.5 * PI ) ) );
+	// texture parameterized by sqrt( GGX alpha ) and sqrt( 1 - cos( theta ) )
+	vec2 uv = vec2( roughness, sqrt( 1.0 - dotNV ) );
 
-	// Ensure we don't have nonlinearities at the look-up table's edges
-	// see: http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter24.html
-	//      "Shader Analysis" section
 	uv = uv * LUT_SCALE + LUT_BIAS;
 
 	return uv;
 
 }
 
-// Real-Time Area Lighting: a Journey from Research to Production
-// By: Stephen Hill & Eric Heitz
-// http://advances.realtimerendering.com/s2016/s2016_ltc_rnd.pdf
-// An approximation for the form factor of a clipped rectangle.
 float LTC_ClippedSphereFormFactor( const in vec3 f ) {
 
+	// Real-Time Area Lighting: a Journey from Research to Production (p.102)
+	// An approximation of the form factor of a horizon-clipped rectangle.
+
 	float l = length( f );
 
 	return max( ( l * l + f.z ) / ( l + 1.0 ), 0.0 );
 
 }
 
-// Real-Time Polygonal-Light Shading with Linearly Transformed Cosines
-// also Real-Time Area Lighting: a Journey from Research to Production
-// http://advances.realtimerendering.com/s2016/s2016_ltc_rnd.pdf
-// Normalization by 2*PI is incorporated in this function itself.
-// theta/sin(theta) is approximated by rational polynomial
 vec3 LTC_EdgeVectorFormFactor( const in vec3 v1, const in vec3 v2 ) {
 
 	float x = dot( v1, v2 );
 
 	float y = abs( x );
-	float a = 0.86267 + (0.49788 + 0.01436 * y ) * y;
-	float b = 3.45068 + (4.18814 + y) * y;
+
+	// rational polynomial approximation to theta / sin( theta ) / 2PI
+	float a = 0.8543985 + ( 0.4965155 + 0.0145206 * y ) * y;
+	float b = 3.4175940 + ( 4.1616724 + y ) * y;
 	float v = a / b;
 
-	float theta_sintheta = (x > 0.0) ? v : 0.5 * inversesqrt( 1.0 - x * x ) - v;
+    float theta_sintheta = ( x > 0.0 ) ? v : 0.5 * inversesqrt( max( 1.0 - x * x, 1e-7 ) ) - v;
 
 	return cross( v1, v2 ) * theta_sintheta;
 
@@ -188,7 +174,7 @@ vec3 LTC_Evaluate( const in vec3 N, const in vec3 V, const in vec3 P, const in m
 	// construct orthonormal basis around N
 	vec3 T1, T2;
 	T1 = normalize( V - N * dot( V, N ) );
-	T2 = - cross( N, T1 ); // negated from paper; possibly due to a different assumed handedness of world coordinate system
+	T2 = - cross( N, T1 ); // negated from paper; possibly due to a different handedness of world coordinate system
 
 	// compute transform
 	mat3 mat = mInv * transposeMat3( mat3( T1, T2, N ) );
@@ -214,9 +200,28 @@ vec3 LTC_Evaluate( const in vec3 N, const in vec3 V, const in vec3 P, const in m
 	vectorFormFactor += LTC_EdgeVectorFormFactor( coords[ 3 ], coords[ 0 ] );
 
 	// adjust for horizon clipping
-	vec3 result = vec3( LTC_ClippedSphereFormFactor( vectorFormFactor ) );
+	float result = LTC_ClippedSphereFormFactor( vectorFormFactor );
+
+/*
+	// alternate method of adjusting for horizon clipping (see referece)
+	// refactoring required
+	float len = length( vectorFormFactor );
+	float z = vectorFormFactor.z / len;
+
+	const float LUT_SIZE  = 64.0;
+	const float LUT_SCALE = ( LUT_SIZE - 1.0 ) / LUT_SIZE;
+	const float LUT_BIAS  = 0.5 / LUT_SIZE;
+
+	// tabulated horizon-clipped sphere, apparently...
+	vec2 uv = vec2( z * 0.5 + 0.5, len );
+	uv = uv * LUT_SCALE + LUT_BIAS;
+
+	float scale = texture2D( ltc_2, uv ).w;
+
+	float result = len * scale;
+*/
 
-	return result;
+	return vec3( result );
 
 }
 

src/renderers/shaders/ShaderChunk/lights_pars.glsl

@@ -132,8 +132,8 @@ vec3 getAmbientLightIrradiance( const in vec3 ambientLightColor ) {
 
 	// Pre-computed values of LinearTransformedCosine approximation of BRDF
 	// BRDF approximation Texture is 64x64
-	uniform sampler2D ltcMat; // RGBA Float
-	uniform sampler2D ltcMag; // Alpha Float (only has w component)
+	uniform sampler2D ltc_1; // RGBA Float
+	uniform sampler2D ltc_2; // RGBA Float
 
 	uniform RectAreaLight rectAreaLights[ NUM_RECT_AREA_LIGHTS ];
 

src/renderers/shaders/ShaderChunk/lights_physical_pars_fragment.glsl

@@ -42,19 +42,22 @@ float clearCoatDHRApprox( const in float roughness, const in float dotNL ) {
 
 		vec2 uv = LTC_Uv( normal, viewDir, roughness );
 
-		float norm = texture2D( ltcMag, uv ).a;
-
-		vec4 t = texture2D( ltcMat, uv );
+		vec4 t1 = texture2D( ltc_1, uv );
+		vec4 t2 = texture2D( ltc_2, uv );
 
 		mat3 mInv = mat3(
-			vec3(   1,   0, t.y ),
-			vec3(   0, t.z,   0 ),
-			vec3( t.w,   0, t.x )
+			vec3( t1.x, 0, t1.y ),
+			vec3(    0, 1,    0 ),
+			vec3( t1.z, 0, t1.w )
 		);
 
-		reflectedLight.directSpecular += lightColor * material.specularColor * norm * LTC_Evaluate( normal, viewDir, position, mInv, rectCoords ); // no fresnel
+		// LTC Fresnel Approximation by Stephen Hill
+		// http://blog.selfshadow.com/publications/s2016-advances/s2016_ltc_fresnel.pdf
+		vec3 fresnel = ( material.specularColor * t2.x + ( vec3( 1.0 ) - material.specularColor ) * t2.y );
+
+		reflectedLight.directSpecular += lightColor * fresnel * LTC_Evaluate( normal, viewDir, position, mInv, rectCoords );
 
-		reflectedLight.directDiffuse += lightColor * material.diffuseColor * LTC_Evaluate( normal, viewDir, position, mat3( 1 ), rectCoords );
+		reflectedLight.directDiffuse += lightColor * material.diffuseColor * LTC_Evaluate( normal, viewDir, position, mat3( 1.0 ), rectCoords );
 
 	}