From c4d0c4af57f3486651ae66811008618bdb9b65d6 Mon Sep 17 00:00:00 2001
From: Hannes Janetzek <hannes.janetzek@gmail.com>
Date: Sat, 11 May 2013 17:28:09 +0200
Subject: [PATCH] fix Matrix functions to use temporary array when lhs or rhs
 are same as result

---
 jni/gl/utils.c                   | 23 +++++++++++++++++++++++
 src/org/oscim/utils/Matrix4.java | 26 ++++++++++++++++++++++----
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/jni/gl/utils.c b/jni/gl/utils.c
index 02e54a95..7e3734d7 100644
--- a/jni/gl/utils.c
+++ b/jni/gl/utils.c
@@ -186,6 +186,29 @@ void JNI(smul)(JNIEnv* env, jclass* clazz, jlong ptr_r, jlong ptr_a, jlong ptr_b
   multiplyMM(matr, mata, matb);
 }
 
+void JNI(smulrhs)(JNIEnv* env, jclass* clazz, jlong ptr_r, jlong ptr_rhs)
+{
+  float* matr = CAST(ptr_r);
+  float* mata = alloca(16 * sizeof(float));
+  float* matb = CAST(ptr_rhs);
+
+  memcpy(mata, matr, 16 * sizeof(float));
+
+  multiplyMM(matr, mata, matb);
+}
+
+void JNI(smullhs)(JNIEnv* env, jclass* clazz, jlong ptr_r, jlong ptr_lhs)
+{
+  float* matr = CAST(ptr_r);
+  float* mata = CAST(ptr_lhs);
+  float* matb = alloca(16 * sizeof(float));
+
+  memcpy(matb, matr, 16 * sizeof(float));
+
+  multiplyMM(matr, mata, matb);
+}
+
+
 void JNI(strans)(JNIEnv* env, jclass* clazz, jlong ptr_r, jlong ptr_a)
 {
   float* matr = CAST(ptr_r);
diff --git a/src/org/oscim/utils/Matrix4.java b/src/org/oscim/utils/Matrix4.java
index 95712116..39cf394f 100644
--- a/src/org/oscim/utils/Matrix4.java
+++ b/src/org/oscim/utils/Matrix4.java
@@ -39,6 +39,10 @@ public class Matrix4 {
 
 	private native static void smul(long self, long rhs_ptr, long lhs_ptr);
 
+	private native static void smulrhs(long self, long rhs_ptr);
+
+	private native static void smullhs(long self, long lhs_ptr);
+
 	private native static void strans(long self, long rhs_ptr);
 
 	private native static void prj(long self, float[] vec3);
@@ -111,16 +115,30 @@ public class Matrix4 {
 	}
 
 	/**
-	 * Multiply rhs onto Matrix
+	 * Multiply rhs onto Matrix.
 	 *
 	 * @param rhs right hand side
 	 */
-	public void multiplyMM(Matrix4 rhs) {
-		smul(pointer, pointer, rhs.pointer);
+	public void multiplyRhs(Matrix4 rhs) {
+		smulrhs(pointer, rhs.pointer);
 	}
 
 	/**
-	 * Multiply rhs onto lhs and store result in Matrix
+	 * Use this matrix as rhs, multiply it on lhs and store result.
+	 *
+	 * @param lhs right hand side
+	 */
+	public void multiplyLhs(Matrix4 lhs) {
+		smullhs(pointer, lhs.pointer);
+	}
+
+	/**
+	 * Multiply rhs onto lhs and store result in Matrix.
+	 *
+	 * This matrix MUST be different from lhs and rhs!
+	 *
+	 * As you know, when combining matrices for vector projection
+	 * this has the same effect first as applying rhs then lhs.
 	 *
 	 * @param lhs left hand side
 	 * @param rhs right hand side