three
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JavaScript 3D library
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JavaScript
import { uv as getUV } from './UV.js';
import { positionView } from './Position.js';
import { normalView } from './Normal.js';
// Normal Mapping Without Precomputed Tangents
// http://www.thetenthplanet.de/archives/1180
const uv = getUV();
const q0 = positionView.dFdx();
const q1 = positionView.dFdy();
const st0 = uv.dFdx();
const st1 = uv.dFdy();
const N = normalView;
const q1perp = q1.cross( N );
const q0perp = N.cross( q0 );
const T = q1perp.mul( st0.x ).add( q0perp.mul( st1.x ) );
const B = q1perp.mul( st0.y ).add( q0perp.mul( st1.y ) );
const det = T.dot( T ).max( B.dot( B ) );
const scale = det.equal( 0.0 ).select( 0.0, det.inverseSqrt() );
/**
* Tangent vector in view space, computed dynamically from geometry and UV derivatives.
* Useful for normal mapping without precomputed tangents.
*
* Reference: http://www.thetenthplanet.de/archives/1180
*
* @tsl
* @type {Node<vec3>}
*/
export const tangentViewFrame = /*@__PURE__*/ T.mul( scale ).toVar( 'tangentViewFrame' );
/**
* Bitangent vector in view space, computed dynamically from geometry and UV derivatives.
* Complements the tangentViewFrame for constructing the tangent space basis.
*
* Reference: http://www.thetenthplanet.de/archives/1180
*
* @tsl
* @type {Node<vec3>}
*/
export const bitangentViewFrame = /*@__PURE__*/ B.mul( scale ).toVar( 'bitangentViewFrame' );