Examples: Add ground projected env map

examples/files.json

@@ -141,6 +141,7 @@
 		"webgl_materials_displacementmap",
 		"webgl_materials_envmaps",
 		"webgl_materials_envmaps_exr",
+		"webgl_materials_envmaps_ground-projected",
 		"webgl_materials_envmaps_hdr",
 		"webgl_materials_lightmap",
 		"webgl_materials_matcap",

examples/jsm/objects/GroundProjectedEnv.js

@@ -0,0 +1,186 @@
+import { Mesh, IcosahedronGeometry, ShaderMaterial, DoubleSide } from 'three';
+
+/**
+ * Ground projected env map adapted from @react-three/drei.
+ * https://github.com/pmndrs/drei/blob/master/src/core/Environment.tsx
+ */
+export class GroundProjectedEnv extends Mesh {
+
+	constructor( texture, options ) {
+
+		const isCubeMap = texture.isCubeTexture;
+		const w =
+			( isCubeMap ? texture.image[ 0 ]?.width : texture.image.width ) ?? 1024;
+		const cubeSize = w / 4;
+		const _lodMax = Math.floor( Math.log2( cubeSize ) );
+		const _cubeSize = Math.pow( 2, _lodMax );
+		const width = 3 * Math.max( _cubeSize, 16 * 7 );
+		const height = 4 * _cubeSize;
+
+		const defines = [
+			isCubeMap ? '#define ENVMAP_TYPE_CUBE' : '',
+			`#define CUBEUV_TEXEL_WIDTH ${1.0 / width}`,
+			`#define CUBEUV_TEXEL_HEIGHT ${1.0 / height}`,
+			`#define CUBEUV_MAX_MIP ${_lodMax}.0`,
+		];
+
+		const vertexShader = /* glsl */ `
+        varying vec3 vWorldPosition;
+
+        void main() 
+        {
+
+            vec4 worldPosition = ( modelMatrix * vec4( position, 1.0 ) );
+            vWorldPosition = worldPosition.xyz;
+
+            gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
+
+        }
+        `;
+		const fragmentShader = defines.join( '\n' ) + /* glsl */ `
+        #define ENVMAP_TYPE_CUBE_UV
+
+        varying vec3 vWorldPosition;
+
+        uniform float radius;
+        uniform float height;
+        uniform float angle;
+
+        #ifdef ENVMAP_TYPE_CUBE
+
+            uniform samplerCube map;
+
+        #else
+
+            uniform sampler2D map;
+
+        #endif
+
+        // From: https://www.shadertoy.com/view/4tsBD7
+        float diskIntersectWithBackFaceCulling( vec3 ro, vec3 rd, vec3 c, vec3 n, float r ) 
+        {
+
+            float d = dot ( rd, n );
+
+            if( d > 0.0 ) { return 1e6; }
+
+            vec3  o = ro - c;
+            float t = - dot( n, o ) / d;
+            vec3  q = o + rd * t;
+
+            return ( dot( q, q ) < r * r ) ? t : 1e6;
+
+        }
+
+        // From: https://www.iquilezles.org/www/articles/intersectors/intersectors.htm
+        float sphereIntersect( vec3 ro, vec3 rd, vec3 ce, float ra ) 
+        {
+
+            vec3 oc = ro - ce;
+            float b = dot( oc, rd );
+            float c = dot( oc, oc ) - ra * ra;
+            float h = b * b - c;
+
+            if( h < 0.0 ) { return -1.0; }
+
+            h = sqrt( h );
+
+            return - b + h;
+
+        }
+
+        vec3 project() 
+        {
+
+            vec3 p = normalize( vWorldPosition );
+            vec3 camPos = cameraPosition;
+            camPos.y -= height;
+
+            float intersection = sphereIntersect( camPos, p, vec3( 0.0 ), radius );
+            if( intersection > 0.0 ) {
+
+                vec3 h = vec3( 0.0, - height, 0.0 );
+                float intersection2 = diskIntersectWithBackFaceCulling( camPos, p, h, vec3( 0.0, 1.0, 0.0 ), radius );
+                p = ( camPos + min( intersection, intersection2 ) * p ) / radius;
+
+            } else {
+
+                p = vec3( 0.0, 1.0, 0.0 );
+
+            }
+
+            return p;
+
+        }
+
+        #include <common>
+        #include <cube_uv_reflection_fragment>
+
+        void main() 
+        {
+
+            vec3 projectedWorldPosition = project();
+
+            #ifdef ENVMAP_TYPE_CUBE
+
+                vec3 outcolor = textureCube( map, projectedWorldPosition ).rgb;
+
+            #else
+
+                vec3 direction = normalize( projectedWorldPosition );
+                vec2 uv = equirectUv( direction );
+                vec3 outcolor = texture2D( map, uv ).rgb;
+
+            #endif
+
+            gl_FragColor = vec4( outcolor, 1.0 );
+
+            #include <tonemapping_fragment>
+            #include <encodings_fragment>
+
+        }
+        `;
+
+		const uniforms = {
+			map: { value: texture },
+			height: { value: options?.height || 15 },
+			radius: { value: options?.radius || 100 },
+		};
+
+		const geometry = new IcosahedronGeometry( 1, 16 );
+		const material = new ShaderMaterial( {
+			uniforms,
+			fragmentShader,
+			vertexShader,
+			side: DoubleSide,
+		} );
+
+		super( geometry, material );
+
+	}
+
+	set radius( radius ) {
+
+		this.material.uniforms.radius.value = radius;
+
+	}
+
+	get radius() {
+
+		return this.material.uniforms.radius.value;
+
+	}
+
+	set height( height ) {
+
+		this.material.uniforms.height.value = height;
+
+	}
+
+	get height() {
+
+		return this.material.uniforms.height.value;
+
+	}
+
+}