--- a/include/material.h	Sat May 10 14:29:37 2008 +0200
+++ b/include/material.h	Thu May 15 00:07:25 2008 +0200
@@ -110,7 +110,7 @@
 	TextureMap(const Vector &acenter, const Float &size):
 		center(acenter), invsize(1.0f/size) {};
 	virtual ~TextureMap() {};
-	virtual void map(const Vector &point, Float &u, Float &v) = 0;
+	virtual void map(const Vector &point, Float &u, Float &v) const = 0;
 };
 
 /**
@@ -121,7 +121,7 @@
 public:
 	PlanarMap(const Vector &acenter, const Float &size):
 		TextureMap(acenter, size) {};
-	void map(const Vector &point, Float &u, Float &v)
+	void map(const Vector &point, Float &u, Float &v) const
 	{
 		const Vector p = point - center;
 		u = p.x*invsize;
@@ -137,7 +137,7 @@
 public:
 	CubicMap(const Vector &acenter, const Float &size):
 		TextureMap(acenter, size) {};
-	void map(const Vector &point, Float &u, Float &v)
+	void map(const Vector &point, Float &u, Float &v) const
 	{
 		const Vector p = point - center;
 		if (fabs(p.x) > fabs(p.y))
@@ -191,7 +191,7 @@
 public:
 	CylinderMap(const Vector &acenter, const Float &size):
 		TextureMap(acenter, size) {};
-	void map(const Vector &point, Float &u, Float &v)
+	void map(const Vector &point, Float &u, Float &v) const
 	{
 		const Vector p = point - center;
 		u = ( PI + atan2(p.z, p.x) ) * invsize;
@@ -207,7 +207,7 @@
 public:
 	SphereMap(const Vector &acenter, const Float &size):
 		TextureMap(acenter, size) {};
-	void map(const Vector &point, Float &u, Float &v)
+	void map(const Vector &point, Float &u, Float &v) const
 	{
 		const Vector p = point - center;
 		u = ( PI + atan2(p.z, p.x) ) * invsize;
@@ -221,9 +221,9 @@
 class Texture2D: public Texture
 {
 protected:
-	TextureMap *map;
+	const TextureMap *map;
 public:
-	Texture2D(TextureMap *amap): map(amap) {};
+	Texture2D(const TextureMap *amap): map(amap) {};
 };
 
 /**
@@ -231,9 +231,9 @@
  */
 class ImageTexture: public Texture2D
 {
-	Pixmap *pixmap;
+	const Pixmap *pixmap;
 public:
-	ImageTexture(TextureMap *tmap, Pixmap *image):
+	ImageTexture(const TextureMap *tmap, const Pixmap *image):
 		Texture2D(tmap), pixmap(image) {};
 	Colour evaluate(const Vector &point)
 	{