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diff --git a/hw6/src/bumpMap.cpp b/hw6/src/bumpMap.cpp
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+/******************************************************************/
+/* This file is part of the homework assignments for CSCI-427/527 */
+/* at The College of William & Mary and authored by Pieter Peers. */
+/* No part of this file, whether altered or in original form, can */
+/* be distributed or used outside the context of CSCI-427/527     */
+/* without consent of either the College of William & Mary or     */
+/* Pieter Peers.                                                  */
+/******************************************************************/
+#include <cassert>
+#include <algorithm>
+#include "bumpMap.h"
+#include "coordinateTransform.h"
+
+//////////////////
+// Constructors //
+//////////////////
+bumpMap::bumpMap(const std::shared_ptr<const texture_base>& map, float scale, unsigned int channel, const std::shared_ptr<const shader_base>& shader)
+  : shadingFrameTransformation(shader)
+{
+  _map = map;
+  _scale = scale;
+  _channel = std::max(channel, 2u);
+}
+
+/////////////
+// Methods //
+/////////////
+transformation3d bumpMap::_transformation(const vec2d& textureCoord) const
+{
+  // get derivative in X and Y direction
+  assert(_map);
+  float dx = (*_map)(textureCoord)[_channel] - (*_map)(textureCoord + vec2d(1.0f/_map->width(), 0.0f))[_channel];
+  float dy = (*_map)(textureCoord)[_channel] - (*_map)(textureCoord + vec2d(0.0f, 1.0f/_map->height()))[_channel];
+
+  // get desired local normal = (1.0, 0.0, dx) cross (0.0, 1.0, dy)
+  vec3d normal(-dx, -dy, 1.0f / _scale);
+  normal.normalize();
+
+  // create coordinate system. Keep U aligned as close as possible to the X axis.
+  return coordinateTransformation(normal, vec3d(1.0f, 0.0, 0.0));
+}
+
+
+void bumpMap::_print(std::ostream& s) const
+{
+  s << "bumpMap (" << _scale << " x " << *_map << "[" << _channel << "]) -> {" << *_shader << "}";
+}
+