From cf31a302f2dfdd422a0017485cdf562f063961d5 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop+git@gmail.com>
Date: Mon, 9 May 2011 17:11:07 -0400
Subject: [PATCH] add guOrtho()

---
 glslUtil/glslUtil.c | 26 ++++++++++++++++++++++++++
 glslUtil/glslUtil.h |  4 ++++
 2 files changed, 30 insertions(+)

diff --git a/glslUtil/glslUtil.c b/glslUtil/glslUtil.c
index 9341264..1a586f1 100644
--- a/glslUtil/glslUtil.c
+++ b/glslUtil/glslUtil.c
@@ -142,3 +142,29 @@ void guPerspective(guMatrix4x4 *m, GLfloat fovy, GLfloat aspect,
     mult[3][2] = -1.0;
     guMatrixMult(m, m, &mult);
 }
+
+void guOrtho(guMatrix4x4 *m,
+        GLfloat left, GLfloat right,
+        GLfloat bottom, GLfloat top,
+        GLfloat near, GLfloat far)
+{
+    int i, j;
+    guMatrix4x4 mult;
+    for (i = 0; i < 4; i++)
+    {
+        for (j = 0; j < 4; j++)
+        {
+            mult[i][j] = 0.0;
+        }
+    }
+    GLfloat rl = right - left;
+    GLfloat tb = top - bottom;
+    GLfloat fn = far - near;
+    mult[0][0] = 2 / rl;
+    mult[0][3] = - (right + left) / rl;
+    mult[1][1] = 2 / tb;
+    mult[1][3] = - (top + bottom) / tb;
+    mult[2][2] = -2 / fn;
+    mult[2][3] = - (far + near) / fn;
+    mult[3][3] = 1.0;
+}
diff --git a/glslUtil/glslUtil.h b/glslUtil/glslUtil.h
index ffc4a4f..040c977 100644
--- a/glslUtil/glslUtil.h
+++ b/glslUtil/glslUtil.h
@@ -26,6 +26,10 @@ void guMatrixFrustum(guMatrix4x4 *m,
         GLfloat near, GLfloat far);
 void guPerspective(guMatrix4x4 *m, GLfloat fovy, GLfloat aspect,
         GLfloat near, GLfloat far);
+void guOrtho(guMatrix4x4 *m,
+        GLfloat left, GLfloat right,
+        GLfloat bottom, GLfloat top,
+        GLfloat near, GLfloat far);
 
 #ifdef __cplusplus
 }