image converter from 'cross format' to multi image

[jeromeetienne]

there is a nice converter of skybox image in webgl_shaders_ocean.html which convert skybox in 'cross' format into multi image ones (the one understood by three.js)

• the image https://github.com/mrdoob/three.js/blob/master/examples/textures/skyboxsun25degtest.png
• the code to convert https://github.com/mrdoob/three.js/blob/master/examples/webgl_shaders_ocean.html#L131

                var loader = new THREE.ImageLoader();
                loader.load( 'textures/skyboxsun25degtest.png', function ( image ) {

                    var getSide = function ( x, y ) {

                        var size = 1024;

                        var canvas = document.createElement( 'canvas' );
                        canvas.width = size;
                        canvas.height = size;

                        var context = canvas.getContext( '2d' );
                        context.drawImage( image, - x * size, - y * size );

                        return canvas;

                    };

                    cubeMap.image[ 0 ] = getSide( 2, 1 ); // px
                    cubeMap.image[ 1 ] = getSide( 0, 1 ); // nx
                    cubeMap.image[ 2 ] = getSide( 1, 0 ); // py
                    cubeMap.image[ 3 ] = getSide( 1, 2 ); // ny
                    cubeMap.image[ 4 ] = getSide( 1, 1 ); // pz
                    cubeMap.image[ 5 ] = getSide( 3, 1 ); // nz
                    cubeMap.needsUpdate = true;

                } );

                var cubeShader = THREE.ShaderLib['cube'];
                cubeShader.uniforms['tCube'].value = cubeMap;

                var skyBoxMaterial = new THREE.ShaderMaterial( {
                    fragmentShader: cubeShader.fragmentShader,
                    vertexShader: cubeShader.vertexShader,
                    uniforms: cubeShader.uniforms,
                    depthWrite: false,
                    side: THREE.BackSide
                });

                var skyBox = new THREE.Mesh(
                    new THREE.BoxGeometry( 1000000, 1000000, 1000000 ),
                    skyBoxMaterial
                );

                scene.add( skyBox );

[jeromeetienne]

It may be interesting to put that somewhere in the module