1 files changed, 31 insertions, 1 deletions
diff --git a/source/math.h b/source/math.h
index fda6bf8..d2b8ed0 100644
--- a/source/math.h
+++ b/source/math.h
@@ -5,6 +5,7 @@
 #define Square(x) ((x)*(x))
 #define To_Radian(x) ((x) * PI / 180.0f)
 #define To_Degree(x) ((x) * 180.0f / PI)
+#define Ortho_Default_H 10.0f
 
 // @notes:
 // I dislike the mat4 discrepancy in the raw data. It's called buffer here while everywhere else it's called
@@ -341,7 +342,7 @@ Mat4 rotation_matrix4m(r32 angle_radians, Vec3 axis)	// generates a 4x4 rotation
 	return res;
 }
 
-Mat4 perspective_projection_matrix4m(r32 left, r32 right, r32 bottom, r32 top, r32 near, r32 far)
+Mat4 perspective_projection4m(r32 left, r32 right, r32 bottom, r32 top, r32 near, r32 far)
 {
 	Mat4 res = { 0 };
 	
@@ -377,6 +378,35 @@ Mat4 perspective4m(r32 fov, r32 aspect_ratio, r32 near, r32 far)
 	return res;
 }
 
+Mat4 orthographic_projection4m(r32 left, r32 right, r32 bottom, r32 top, r32 near, r32 far)
+{
+  // @todo: understand the derivation once I am done experimenting
+  Mat4 res = { 0 };
+  res.data[0][0] = 2.0f/(right - left);   res.data[0][3] = -(right + left)/(right - left);
+  res.data[1][1] = 2.0f/(top - bottom);   res.data[1][3] = -(top + bottom)/(top - bottom);
+  res.data[2][2] = -2.0f/(far - near);    res.data[2][3] = -(far + near)/(far - near);
+  res.data[3][3] = 1.0f;
+
+  return res;
+}
+
+// @note: takes the screen width, screen height, near and far values, and creates an orthographic projection matrix
+// height: arbitrary and depend on the user/camera creator.
+// aspect_ratio: width/height, this too is user defined.
+// near, far: values of the near and far plane
+Mat4 orthographic4m(r32 height, r32 aspect_ratio, r32 near, r32 far)
+{
+  r32 width  = height * aspect_ratio;
+
+  r32 left   = -width/2.0f;
+  r32 right  =  width/2.0f;
+
+  r32 bottom = -height/2.0f;
+  r32 top    =  height/2.0f;
+
+  return orthographic_projection4m(left, right, bottom, top, near, far);
+}
+
 Mat4 lookat4m(Vec3 up, Vec3 forward, Vec3 right, Vec3 position)
 {
 	/*