matrix_ortho.gml

///matrix_ortho(x,y, width,height, znear,zfar)
// Thanks, mesa! 
// Source from src/mesa/math/m_matrix.c:1019

// Modified according to the formula at the bottom of 
// https://msdn.microsoft.com/en-us/library/windows/desktop/bb205347(v=vs.85).aspx

var _x,_y,w,h;
_x = argument0;
_y = argument1;
w = argument2;
h = argument3;

var m, left, right, bottom, top, nearval, farval; 
left = _x-w/2;
right = _x+w/2;
bottom = _y+h/2;
top = _y-h/2;
nearval = argument4;
farval = argument5;

// #define M(row,col)  m[col*4+row]
m[0 + 4*0] = 2.0 / (right-left);
m[0 + 4*1] = 0.0;
m[0 + 4*2] = 0.0;
m[0 + 4*3] = (left+right) / (left-right);

m[1 + 4*0] = 0.0;
m[1 + 4*1] = 2.0 / (top-bottom);
m[1 + 4*2] = 0.0;
m[1 + 4*3] = (top+bottom) / (bottom-top);

m[2 + 4*0] = 0.0;
m[2 + 4*1] = 0.0;
m[2 + 4*2] = 1 / (farval-nearval);
m[2 + 4*3] = nearval / (nearval-farval);

m[3 + 4*0] = 0.0;
m[3 + 4*1] = 0.0;
m[3 + 4*2] = 0.0;
m[3 + 4*3] = 1.0;

return m;