Improved MatrixStack performance

include/ACGL/Scene/MatrixStack.hh

@@ -74,29 +74,42 @@ public:
     // will replace the top matrix with the given matrix
     void loadMatrix( glm::mat4 matrixToLoad )
     {
-        popMatrix();
+        if (!mStack.empty()) {
+            mStack.top() = matrixToLoad;
+        } else {
             mStack.push( matrixToLoad );
         }
+    }
 
     // the top matrix will be multiplied with the given one and
     // will then replace the top matrix
     void multMatrix( const glm::mat4 &rhs )
     {
-        mStack.push( popAndGetMatrix() * rhs );
+        if (mStack.empty()) mStack.push( glm::mat4() );
+        mStack.top() *= rhs;
+    }
+
+    // pushes the product of top and rhs
+    void pushAndMultMatrix( const glm::mat4 &rhs )
+    {
+        if (mStack.empty()) mStack.push( glm::mat4() );
+        mStack.push( mStack.top() * rhs );
     }
 
     // like glRotate rotates the top matrix around a given axis a given degree phi
     void rotate(const float phi, const float x, const float y, const float z) { rotate( phi, glm::vec3( x,y,z )); }
     void rotate(const float phi, const glm::vec3 &axis )
     {
-        mStack.push( glm::rotate( popAndGetMatrix(), phi, axis ) );
+        if (mStack.empty()) mStack.push( glm::mat4() );
+        mStack.top() = glm::rotate( mStack.top(), phi, axis );
     }
 
     // like glTranslate
     void translate(float x, float y, float z) { translate( glm::vec3(x,y,z) ); }
     void translate( glm::vec3 vector )
     {
-        mStack.push( glm::translate( popAndGetMatrix(), vector) );
+        if (mStack.empty()) mStack.push( glm::mat4() );
+        mStack.top() = glm::translate( mStack.top(), vector );
     }
 
     // like glScale
@@ -104,7 +117,8 @@ public:
     void scale( float x, float y, float z ) { scale( glm::vec3(x,y,z)); }
     void scale( const glm::vec3 &factor )
     {
-        mStack.push( glm::scale( popAndGetMatrix(), factor ) );
+        if (mStack.empty()) mStack.push( glm::mat4() );
+        mStack.top() = glm::scale( mStack.top(), factor );
     }
 
 private: