正交矩阵

只需将空间坐标转换为[-1,1]之间并移到中心位置,l = left,r =right,t = top,b = bottom ,n = near, f = far。

2/(r - l) 0 0 0
0 2/(t-b) 0 0
0 0 2/(f-n) 0
0 0 0 1
*
1 0 0 -(r+l)/2
0 1 0 -(t+b)/2
0 0 1 -(f+n)/2
0 0 0 1
=
2/(r - l) 0 0 -(r+l)/(r-l)
0 2/(t - b) 0 -(t+b)/(t-b)
0 0 2/(f - n) -(f+n)/(f-n)
0 0 0 1

实现代码

/**
 * @param {number} left Left bound of the frustum
 * @param {number} right Right bound of the frustum
 * @param {number} bottom Bottom bound of the frustum
 * @param {number} top Top bound of the frustum
 * @param {number} near Near bound of the frustum
 * @param {number} far Far bound of the frustum
 * @returns {Array} out
 */
function ortho(left, right, bottom, top, near, far){
	let subRL = right - left,subTB = top - bottom,subFN = far - near;
	let addRL = right + left,addTB = top + bottom,addFN = far + near;
		
    out[0] = 2 * subRL;
    out[1] = 0;
    out[2] = 0;
    out[3] = 0;
    out[4] = 0;
    out[5] = 2 * subTB;
    out[6] = 0;
    out[7] = 0;
    out[8] = 0;
    out[9] = 0;
    out[10] = 2 * subFN;
    out[11] = 0;
    out[12] = -addRL * subRL;
    out[13] = -addTB * subTB;
    out[14] = -addFN * subFN ;
    out[15] = 1;
    return out;
}