projection.js

SolvespaceCamera.prototype.updateProjectionMatrix = function() {
    temp = new THREE.Matrix4();
    offset = new THREE.Matrix4().makeTranslation(this.offset.x, this.offset.y, this.offset.z);
    n = new THREE.Vector3().crossVectors(this.right, this.up);
    rotate = new THREE.Matrix4().makeBasis(this.right, this.up, n);
    /* TODO: If we want perspective, we need an additional matrix
    here which will modify w for perspective divide. */
    scale = new THREE.Matrix4().makeScale(2*this.zoom_scale, 2*this.zoom_scale, this.zoom_scale);

    /* FIXME: Where did the negative sign in the zScale come from?
    It's not in Solvespace, but it's required here to prevent the depth buffer
    from being reversed. */
    render_correct = new THREE.Matrix4()
                          .makeScale(1/this.render_width, 1/this.render_height,
                          -1/30000.0);

    /* FIXME: This adds a (negative, thanks to scaling) bias to the
    z coordinate to push certain layers (edges) closer to the front of the
    screen. Biases don't match solvespace because solvespace uses Open GL
    1.0's glDepthRange to change the offset/normalization. We do it manually
    here. Solvespace uses a depth_bias of 2/60000 for edges. This also works
    here, but it looks bad. */
    depth_correct = new THREE.Matrix4().makeTranslation(0, 0, this.depth_bias);
    temp.multiply( offset );
    temp.multiply( rotate );
    temp.multiply( scale );
    temp.multiply( render_correct );
    temp.multiply( depth_correct );


    this.projectionMatrix.copy( temp );
};