63 lines
2.1 KiB
JavaScript
63 lines
2.1 KiB
JavaScript
import { Fn, If, vec3, float, min, cameraPosition, positionWorld } from 'three/tsl';
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/**
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* @module GroundedSkybox
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* @three_import import { getGroundProjectedNormal } from 'three/addons/tsl/utils/GroundedSkybox.js';
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*/
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/**
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* Projects the world position onto a sphere whose bottom is clipped by a ground disk,
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* then returns a vector usable for sampling an environment cube map.
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*
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* @tsl
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* @function
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* @param {Node<float>} radiusNode - The radius of the projection sphere. Must be large enough to ensure the scene's camera stays inside.
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* @param {Node<float>} heightNode - The height is how far the camera that took the photo was above the ground. A larger value will magnify the downward part of the image.
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* @return {Node<vec3>} A direction vector for sampling the environment cube map.
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*/
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export const getGroundProjectedNormal = Fn( ( [ radiusNode, heightNode ] ) => {
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const p = positionWorld.sub( cameraPosition ).normalize().toConst();
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const camPos = cameraPosition.toVar();
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camPos.y.subAssign( heightNode );
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// sphereIntersect( camPos, p, vec3( 0 ), radius )
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const b = camPos.dot( p ).toConst();
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const c = camPos.dot( camPos ).sub( radiusNode.mul( radiusNode ) ).toConst();
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const h = b.mul( b ).sub( c ).toConst();
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const intersection = h.greaterThanEqual( 0 ).select( h.sqrt().sub( b ), - 1 );
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const projected = vec3( 0, 1, 0 ).toVar();
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If( intersection.greaterThan( 0 ), () => {
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// diskIntersectWithBackFaceCulling( camPos, p, diskCenter, n, radius )
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const diskCenter = vec3( 0, heightNode.negate(), 0 ).toConst();
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const n = vec3( 0, 1, 0 ).toConst();
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const d = p.dot( n ).toConst();
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const intersection2 = float( 1e6 ).toVar();
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If( d.lessThanEqual( 0 ), () => {
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const o = camPos.sub( diskCenter ).toConst();
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const t = n.dot( o ).negate().div( d ).toConst();
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const q = o.add( p.mul( t ) ).toConst();
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If( q.dot( q ).lessThan( radiusNode.mul( radiusNode ) ), () => {
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intersection2.assign( t );
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} );
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} );
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projected.assign( camPos.add( p.mul( min( intersection, intersection2 ) ) ).div( radiusNode ) );
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} );
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return projected;
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} );
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