# all files / src/vr/ CardboardDistorter.js

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2.41% Lines 2/83

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     // https://github.com/googlevr/webvr-polyfill/blob/master/src/cardboard-distorter.js

    // Use webvr may have scale problem.
    // https://github.com/googlevr/webvr-polyfill/issues/140
    // https://github.com/googlevr/webvr-polyfill/search?q=SCALE&type=Issues&utf8=%E2%9C%93
    // https://github.com/googlevr/webvr-polyfill/issues/147

    import Mesh from '../Mesh';
    import Material from '../Material';
    import Geometry from '../Geometry';
    import Shader from '../Shader';
    import Base from '../core/Base';
    import PerspectiveCamera from '../camera/Perspective';

    import outputEssl from './output.glsl.js';

    Shader.import(outputEssl);

    function lerp (a, b, t) {
        return a * (1 - t) + b * t;
    }

    var CardboardDistorter = Base.extend(function () {
        return {

            clearColor: [0, 0, 0, 1],

            _mesh: new Mesh({
                geometry: new Geometry({
                    dynamic: true
                }),
                culling: false,
                material: new Material({
                    // FIXME Why disable depthMask will be wrong
                    // depthMask: false,
                    depthTest: false,
                    shader: new Shader({
                        vertex: Shader.source('clay.vr.disorter.output.vertex'),
                        fragment: Shader.source('clay.vr.disorter.output.fragment')
                    })
                })
            }),
            _fakeCamera: new PerspectiveCamera()
        };
    }, {

        render: function (renderer, sourceTexture) {
            var clearColor = this.clearColor;
            var gl = renderer.gl;
            gl.clearColor(clearColor[0], clearColor[1], clearColor[2], clearColor[3]);
            gl.clear(gl.COLOR_BUFFER_BIT);

            gl.disable(gl.BLEND);

            this._mesh.material.set('texture', sourceTexture);

            // Full size?
            renderer.saveViewport();
            renderer.setViewport(0, 0, renderer.getWidth(), renderer.getHeight());
            renderer.renderPass([this._mesh], this._fakeCamera);
            renderer.restoreViewport();
            // this._mesh.material.shader.bind(renderer);
            // this._mesh.material.bind(renderer);
            // this._mesh.render(renderer.gl);
        },

        updateFromVRDisplay: function (vrDisplay) {

            // FIXME
            if (vrDisplay.deviceInfo_) {
                // Hardcoded mesh size
                this._updateMesh(20, 20, vrDisplay.deviceInfo_);
            }
            else {
                console.warn('Cant get vrDisplay.deviceInfo_, seems code changed');
            }
        },

        _updateMesh: function (width, height, deviceInfo) {

            var positionAttr = this._mesh.geometry.attributes.position;
            var texcoordAttr = this._mesh.geometry.attributes.texcoord0;
            positionAttr.init(2 * width * height);
            texcoordAttr.init(2 * width * height);

            var lensFrustum = deviceInfo.getLeftEyeVisibleTanAngles();
            var noLensFrustum = deviceInfo.getLeftEyeNoLensTanAngles();
            var viewport = deviceInfo.getLeftEyeVisibleScreenRect(noLensFrustum);
            var vidx = 0;

            var pos = [];
            var uv = [];

            // Vertices
            for (var e = 0; e < 2; e++) {
                for (var j = 0; j < height; j++) {
                    for (var i = 0; i < width; i++, vidx++) {
                        var u = i / (width - 1);
                        var v = j / (height - 1);

                        // Grid points regularly spaced in StreoScreen, and barrel distorted in
                        // the mesh.
                        var s = u;
                        var t = v;
                        var x = lerp(lensFrustum[0], lensFrustum[2], u);
                        var y = lerp(lensFrustum[3], lensFrustum[1], v);
                        var d = Math.sqrt(x * x + y * y);
                        var r = deviceInfo.distortion.distortInverse(d);
                        var p = x * r / d;
                        var q = y * r / d;
                        u = (p - noLensFrustum[0]) / (noLensFrustum[2] - noLensFrustum[0]);
                        v = (q - noLensFrustum[3]) / (noLensFrustum[1] - noLensFrustum[3]);

                        // Convert u,v to mesh screen coordinates.
                        var aspect = deviceInfo.device.widthMeters / deviceInfo.device.heightMeters;

                        // FIXME: The original Unity plugin multiplied U by the aspect ratio
                        // and didn't multiply either value by 2, but that seems to get it
                        // really close to correct looking for me. I hate this kind of "Don't
                        // know why it works" code though, and wold love a more logical
                        // explanation of what needs to happen here.
                        u = (viewport.x + u * viewport.width - 0.5) * 2.0; //* aspect;
                        v = (viewport.y + v * viewport.height - 0.5) * 2.0;

                        pos[0] = u;
                        pos[1] = v;
                        pos[2] = 0;

                        uv[0] = s * 0.5 + e * 0.5;
                        uv[1] = t;

                        positionAttr.set(vidx, pos);
                        texcoordAttr.set(vidx, uv);
                    }
                }

                var w = lensFrustum[2] - lensFrustum[0];
                lensFrustum[0] = -(w + lensFrustum[0]);
                lensFrustum[2] = w - lensFrustum[2];
                w = noLensFrustum[2] - noLensFrustum[0];
                noLensFrustum[0] = -(w + noLensFrustum[0]);
                noLensFrustum[2] = w - noLensFrustum[2];
                viewport.x = 1 - (viewport.x + viewport.width);
            }

            // Indices
            var indices = new Uint16Array(2 * (width - 1) * (height - 1) * 6);
            var halfwidth = width / 2;
            var halfheight = height / 2;
            var vidx = 0;
            var iidx = 0;
            for (var e = 0; e < 2; e++) {
                for (var j = 0; j < height; j++) {
                    for (var i = 0; i < width; i++, vidx++) {
                        if (i === 0 || j === 0) {
                            continue;
                        }
                        // Build a quad.  Lower right and upper left quadrants have quads with
                        // the triangle diagonal flipped to get the vignette to interpolate
                        // correctly.
                        if ((i <= halfwidth) == (j <= halfheight)) {
                            // Quad diagonal lower left to upper right.
                            indices[iidx++] = vidx;
                            indices[iidx++] = vidx - width - 1;
                            indices[iidx++] = vidx - width;
                            indices[iidx++] = vidx - width - 1;
                            indices[iidx++] = vidx;
                            indices[iidx++] = vidx - 1;
                        }
                        else {
                            // Quad diagonal upper left to lower right.
                            indices[iidx++] = vidx - 1;
                            indices[iidx++] = vidx - width;
                            indices[iidx++] = vidx;
                            indices[iidx++] = vidx - width;
                            indices[iidx++] = vidx - 1;
                            indices[iidx++] = vidx - width - 1;
                        }
                    }
                }
            }

            this._mesh.geometry.indices = indices;

            this._mesh.geometry.dirty();
        }
    });

    export default CardboardDistorter;