when drawing background texture, how does its orthographic projection matrix computed? it gave as below ``` static const GLfloat proj[] = { 0, -2.f/w, 0, 0, -2.f/h, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1 }; ``` but I found the orthographic projection matrix has the structure like this: [https://www.scratchapixel.com/lessons/3d-basic-rendering/perspective-and-orthographic-projection-matrix/orthographic-projection-matrix](url) ``` [ 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 ] ```