for convenience: support matrix-vector multiplication directly in the dense matrix classes

include/mitsuba/core/matrix.h

@@ -412,6 +412,15 @@ public:
 		target.m[1][0] = -m[1][0] * invDet;
 		return true;
 	}
+
+	/// Matrix-vector multiplication
+    inline Vector2 operator*(const Vector2 &v) const {
+		return Vector2(
+			m[0][0] * v.x + m[0][1] * v.y,
+			m[1][0] * v.x + m[1][1] * v.y
+		);
+	}
+
 };
 
 /**
@@ -448,6 +457,14 @@ public:
 			  - (m[0][1] * (m[1][0] * m[2][2] - m[1][2] * m[2][0]))
 			  + (m[0][2] * (m[1][0] * m[2][1] - m[1][1] * m[2][0])));
 	}
+
+	/// Matrix-vector multiplication
+    inline Vector operator*(const Vector &v) const {
+		return Vector(
+			m[0][0] * v.x + m[0][1] * v.y + m[0][2] * v.z,
+			m[1][0] * v.x + m[1][1] * v.y + m[1][2] * v.z,
+			m[2][0] * v.x + m[2][1] * v.y + m[2][2] * v.z);
+	}
 };
 
 
@@ -487,6 +504,16 @@ struct MTS_EXPORT_CORE Matrix4x4 : public Matrix<4, 4, Float> {
 			  - (m[0][1] * (m[1][0] * m[2][2] - m[1][2] * m[2][0]))
 			  + (m[0][2] * (m[1][0] * m[2][1] - m[1][1] * m[2][0])));
 	}
+
+	/// Matrix-vector multiplication
+    inline Vector4 operator*(const Vector4 &v) const {
+		return Vector4(
+			m[0][0] * v.x + m[0][1] * v.y + m[0][2] * v.z + m[0][3] * v.w,
+			m[1][0] * v.x + m[1][1] * v.y + m[1][2] * v.z + m[1][3] * v.w,
+			m[2][0] * v.x + m[2][1] * v.y + m[2][2] * v.z + m[2][3] * v.w,
+			m[3][0] * v.x + m[3][1] * v.y + m[3][2] * v.z + m[3][3] * v.w
+		);
+	}
 };
 
 MTS_NAMESPACE_END