shaders/StereographicShader.js

/**
 * Stereographic projection shader
 * based on http://notlion.github.io/streetview-stereographic
 * @author pchen66
 */

import * as THREE from 'three';

/**
 * @description Stereograhpic Shader
 * @module StereographicShader
 * @property {object} uniforms
 * @property {THREE.Texture} uniforms.tDiffuse diffuse map
 * @property {number} uniforms.resolution image resolution
 * @property {THREE.Matrix4} uniforms.transform transformation matrix
 * @property {number} uniforms.zoom image zoom factor
 * @property {number} uniforms.opacity image opacity
 * @property {string} vertexShader vertex shader
 * @property {string} fragmentShader fragment shader
 */
const StereographicShader = {

    uniforms: {

        'tDiffuse': { value: new THREE.Texture() },
        'resolution': { value: 1.0 },
        'transform': { value: new THREE.Matrix4() },
        'zoom': { value: 1.0 },
        'opacity': { value: 1.0 }

    },

    vertexShader: `

        varying vec2 vUv;

        void main() {

            vUv = uv;
            gl_Position = vec4( position, 1.0 );

        }

    `,

    fragmentShader: `

        uniform sampler2D tDiffuse;
        uniform float resolution;
        uniform mat4 transform;
        uniform float zoom;
        uniform float opacity;

        varying vec2 vUv;

        const float PI = 3.141592653589793;

        void main(){

            vec2 position = -1.0 +  2.0 * vUv;

            position *= vec2( zoom * resolution, zoom * 0.5 );

            float x2y2 = position.x * position.x + position.y * position.y;
            vec3 sphere_pnt = vec3( 2. * position, x2y2 - 1. ) / ( x2y2 + 1. );

            sphere_pnt = vec3( transform * vec4( sphere_pnt, 1.0 ) );

            vec2 sampleUV = vec2(
                (atan(sphere_pnt.y, sphere_pnt.x) / PI + 1.0) * 0.5,
                (asin(sphere_pnt.z) / PI + 0.5)
            );

            gl_FragColor = texture2D( tDiffuse, sampleUV );
            gl_FragColor.a *= opacity;

        }
    `
};

export { StereographicShader };