# Orthographic Projection Issue

I have a problem with my Ortho Matrix. The engine uses the perspective projection fine but for some reason the Ortho matrix is messed up. (See screenshots below).

Can anyone understand what is happening here?

At the min I am taking the Projection matrix * Transform (Translate, rotate, scale) and passing to the Vertex shader to multiply the Vertices by it.

``````void Matrix4f::InitOrthoProjTransform(float left, float right, float top, float bottom, float zNear, float zFar)
{
m[0][0] = 2 / (right - left);
m[0][1] = 0;
m[0][2] = 0;
m[0][3] = 0;

m[1][0] = 0;
m[1][1] = 2 / (top - bottom);
m[1][2] = 0;
m[1][3] = 0;

m[2][0] = 0;
m[2][1] = 0;
m[2][2] = -1 / (zFar - zNear);
m[2][3] = 0;

m[3][0] = -(right + left) / (right - left);
m[3][1] = -(top + bottom) / (top - bottom);
m[3][2] = -zNear / (zFar - zNear);
m[3][3] = 1;
}
``````

[ATTACH=CONFIG]712[/ATTACH][ATTACH=CONFIG]713[/ATTACH]

Video: (Same scene but rotating on Y axis)

I’m not sure your ortho matrix is correct. This is what glOrtho uses:

``````
2
------------       0              0              tx
right - left

2
0         ------------        0              ty
top - bottom

-2
0              0         ------------        tz
zFar-zNear

0              0              0              1

where
tx = - (right + left) / (right - left)
ty = - (top + bottom) / (top - bottom)
tz = - (zFar + zNear) / (zFar - zNear)

``````

I’m looking specifically at:

``````
m[2][2] = -1 / (zFar - zNear);
m[3][2] = -zNear / (zFar - zNear);

``````