47 lines
1.3 KiB
JavaScript
47 lines
1.3 KiB
JavaScript
import { uv as getUV } from './UV.js';
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import { positionView } from './Position.js';
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import { normalView } from './Normal.js';
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// Normal Mapping Without Precomputed Tangents
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// http://www.thetenthplanet.de/archives/1180
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const uv = getUV();
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const q0 = positionView.dFdx();
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const q1 = positionView.dFdy();
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const st0 = uv.dFdx();
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const st1 = uv.dFdy();
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const N = normalView;
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const q1perp = q1.cross( N );
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const q0perp = N.cross( q0 );
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const T = q1perp.mul( st0.x ).add( q0perp.mul( st1.x ) );
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const B = q1perp.mul( st0.y ).add( q0perp.mul( st1.y ) );
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const det = T.dot( T ).max( B.dot( B ) );
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const scale = det.equal( 0.0 ).select( 0.0, det.inverseSqrt() );
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/**
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* Tangent vector in view space, computed dynamically from geometry and UV derivatives.
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* Useful for normal mapping without precomputed tangents.
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*
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* Reference: http://www.thetenthplanet.de/archives/1180
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*
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* @tsl
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* @type {Node<vec3>}
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*/
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export const tangentViewFrame = /*@__PURE__*/ T.mul( scale ).toVar( 'tangentViewFrame' );
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/**
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* Bitangent vector in view space, computed dynamically from geometry and UV derivatives.
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* Complements the tangentViewFrame for constructing the tangent space basis.
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*
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* Reference: http://www.thetenthplanet.de/archives/1180
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*
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* @tsl
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* @type {Node<vec3>}
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*/
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export const bitangentViewFrame = /*@__PURE__*/ B.mul( scale ).toVar( 'bitangentViewFrame' );
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