From 2cadec3bed920cd72f50f56d793eebf4623a424d Mon Sep 17 00:00:00 2001
From: Caspian Rychlik-Prince <cprince@puppygames.net>
Date: Sat, 24 Aug 2002 21:35:20 +0000
Subject: [PATCH] Determinants

---
 src/java/org/lwjgl/vector/Matrix3f.java | 19 ++++++++++++----
 src/java/org/lwjgl/vector/Matrix4f.java | 30 ++++++++++++++++++++++++-
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/src/java/org/lwjgl/vector/Matrix3f.java b/src/java/org/lwjgl/vector/Matrix3f.java
index 9cf4bd47..809abf06 100644
--- a/src/java/org/lwjgl/vector/Matrix3f.java
+++ b/src/java/org/lwjgl/vector/Matrix3f.java
@@ -288,10 +288,10 @@ public class Matrix3f {
 	 * @return the transposed matrix
 	 */
 	public Matrix3f transpose(Matrix3f dest) {
-		
+
 		if (dest == null)
 			dest = new Matrix3f();
-		
+
 		if (this != dest) {
 			m00 = dest.m00;
 			m01 = dest.m10;
@@ -304,9 +304,20 @@ public class Matrix3f {
 			m22 = dest.m22;
 		} else
 			transpose();
-		
+
 		return this;
-		
+
+	}
+
+	/**
+	 * @return the determinant of the matrix
+	 */
+	public float determinant() {
+		float f =
+			m00 * (m11 * m22 - m12 * m21)
+				+ m01 * (m12 * m20 - m10 * m22)
+				+ m02 * (m10 * m21 - m11 * m20);
+		return f;
 	}
 
 	/**
diff --git a/src/java/org/lwjgl/vector/Matrix4f.java b/src/java/org/lwjgl/vector/Matrix4f.java
index dc9ebd8f..73480bfa 100644
--- a/src/java/org/lwjgl/vector/Matrix4f.java
+++ b/src/java/org/lwjgl/vector/Matrix4f.java
@@ -395,9 +395,37 @@ public class Matrix4f {
 			m33 = dest.m33;
 		} else
 			transpose();
-		
+
 		return dest;
 	}
+
+	/**
+	 * @return the determinant of the matrix
+	 */
+	public float determinant() {
+		float f =
+			m00
+				* ((m11 * m22 * m33 + m12 * m23 * m31 + m13 * m21 * m32)
+					- m13 * m22 * m31
+					- m11 * m23 * m32
+					- m12 * m21 * m33);
+		f -= m01
+			* ((m10 * m22 * m33 + m12 * m23 * m30 + m13 * m20 * m32)
+				- m13 * m22 * m30
+				- m10 * m23 * m32
+				- m12 * m20 * m33);
+		f += m02
+			* ((m10 * m21 * m33 + m11 * m23 * m30 + m13 * m20 * m31)
+				- m13 * m21 * m30
+				- m10 * m23 * m31
+				- m11 * m20 * m33);
+		f -= m03
+			* ((m10 * m21 * m32 + m11 * m22 * m30 + m12 * m20 * m31)
+				- m12 * m21 * m30
+				- m10 * m22 * m31
+				- m11 * m20 * m32);
+		return f;
+	}
 		
 
 	/**