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122 lines
3.8 KiB
122 lines
3.8 KiB
import { ShaderNode,
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add, addTo, sub, mul, div, saturate, dot, pow, pow2, exp2, normalize, max, sqrt, negate,
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cond, greaterThan, and,
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transformedNormalView, positionViewDirection,
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diffuseColor, specularColor, roughness,
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PI, RECIPROCAL_PI, EPSILON
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} from '../ShaderNode.js';
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export const F_Schlick = new ShaderNode( ( inputs ) => {
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const { f0, f90, dotVH } = inputs;
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// Original approximation by Christophe Schlick '94
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// float fresnel = pow( 1.0 - dotVH, 5.0 );
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// Optimized variant (presented by Epic at SIGGRAPH '13)
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// https://cdn2.unrealengine.com/Resources/files/2013SiggraphPresentationsNotes-26915738.pdf
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const fresnel = exp2( mul( sub( mul( - 5.55473, dotVH ), 6.98316 ), dotVH ) );
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return add( mul( f0, sub( 1.0, fresnel ) ), mul( f90, fresnel ) );
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} ); // validated
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export const BRDF_Lambert = new ShaderNode( ( inputs ) => {
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return mul( RECIPROCAL_PI, inputs.diffuseColor ); // punctual light
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} ); // validated
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export const getDistanceAttenuation = new ShaderNode( ( inputs ) => {
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const { lightDistance, cutoffDistance, decayExponent } = inputs;
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return cond(
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and( greaterThan( cutoffDistance, 0 ), greaterThan( decayExponent, 0 ) ),
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pow( saturate( add( div( negate( lightDistance ), cutoffDistance ), 1.0 ) ), decayExponent ),
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1.0
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);
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} ); // validated
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//
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// STANDARD
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//
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// Moving Frostbite to Physically Based Rendering 3.0 - page 12, listing 2
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// https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
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export const V_GGX_SmithCorrelated = new ShaderNode( ( inputs ) => {
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const { alpha, dotNL, dotNV } = inputs;
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const a2 = pow2( alpha );
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const gv = mul( dotNL, sqrt( add( a2, mul( sub( 1.0, a2 ), pow2( dotNV ) ) ) ) );
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const gl = mul( dotNV, sqrt( add( a2, mul( sub( 1.0, a2 ), pow2( dotNL ) ) ) ) );
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return div( 0.5, max( add( gv, gl ), EPSILON ) );
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} ); // validated
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// Microfacet Models for Refraction through Rough Surfaces - equation (33)
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// http://graphicrants.blogspot.com/2013/08/specular-brdf-reference.html
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// alpha is "roughness squared" in Disney’s reparameterization
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export const D_GGX = new ShaderNode( ( inputs ) => {
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const { alpha, dotNH } = inputs;
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const a2 = pow2( alpha );
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const denom = add( mul( pow2( dotNH ), sub( a2, 1.0 ) ), 1.0 ); // avoid alpha = 0 with dotNH = 1
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return mul( RECIPROCAL_PI, div( a2, pow2( denom ) ) );
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} ); // validated
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// GGX Distribution, Schlick Fresnel, GGX_SmithCorrelated Visibility
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export const BRDF_Specular_GGX = new ShaderNode( ( inputs ) => {
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const { lightDirection, f0, f90, roughness } = inputs;
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const alpha = pow2( roughness ); // UE4's roughness
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const halfDir = normalize( add( lightDirection, positionViewDirection ) );
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const dotNL = saturate( dot( transformedNormalView, lightDirection ) );
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const dotNV = saturate( dot( transformedNormalView, positionViewDirection ) );
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const dotNH = saturate( dot( transformedNormalView, halfDir ) );
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const dotVH = saturate( dot( positionViewDirection, halfDir ) );
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const F = F_Schlick( { f0, f90, dotVH } );
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const V = V_GGX_SmithCorrelated( { alpha, dotNL, dotNV } );
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const D = D_GGX( { alpha, dotNH } );
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return mul( F, mul( V, D ) );
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} ); // validated
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export const RE_Direct_Physical = new ShaderNode( ( inputs ) => {
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const { lightDirection, lightColor, directDiffuse, directSpecular } = inputs;
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const dotNL = saturate( dot( transformedNormalView, lightDirection ) );
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let irradiance = mul( dotNL, lightColor );
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irradiance = mul( irradiance, PI ); // punctual light
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addTo( directDiffuse, mul( irradiance, BRDF_Lambert( { diffuseColor } ) ) );
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addTo( directSpecular, mul( irradiance, BRDF_Specular_GGX( { lightDirection, f0: specularColor, f90: 1, roughness } ) ) );
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} );
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export const PhysicalLightingModel = new ShaderNode( ( inputs/*, builder*/ ) => {
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// PHYSICALLY_CORRECT_LIGHTS <-> builder.renderer.physicallyCorrectLights === true
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RE_Direct_Physical( inputs );
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} );
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