Choosing RGBA vs Color Index Mode Most of the time RGBA is the obvious choice Advanced OGL features (lighting, texturing, fog ....)  are supported  Certain circumstances may encourage CI mode Limited HW visuals (fewer shades of a single component) Color map animation

	Switching  between CI and RGB mode Unfortunately, you can't  A window is bound to a visual during initalization Separate windows may be specified however ...

Specifying Color The current color is an OpenGL state variable   set_color(RED);  draw_item(A);  draw_item(B);  set_color(GREEN);  set_color(BLUE);  draw_item(C);  RGBA Mode:   void glColor3{b s i f d ub us ui} (TYPEr, TYPEg, TYPEb);  void glColor4{b s i f d ub us ui} (TYPEr, TYPEg, TYPEb, TYPEa);  void glColor3{b s i f d ub us ui}v (const TYPE*v);  void glColor4{b s i f d ub us ui}v (const TYPE*v);  Color Index Mode   void glIndex{sifd ub}(TYPE c);  void glIndex{sifd ub}v(const TYPE *c); Clear color: void glClearIndex(GLfloat cindex); NOTE!  There are NO OpenGL commands to load colormap table values (this is a function of the window manager).  The GLUT API provides glutSetColor() to interface with the WM.

	Specifying a Shading Model How an object is colored is specified with glShadeModel ( GL_SMOOTH| GL_FLAT)  Smooth shading will interpolate the vertex values across the polygon with Gouraud shading This can be problimatic for CI mode (choose your colormap carefully!) Flat shading will color the entire primitive the same color Image from: http://www.cognivis.com/book/rend.htm

	Homework Modify the glutSpin application to render the color of each vertex based on its height   Extra credit:   carefully choose colors which enhance the perception of the shape of the surface Modify the color array to determine your ability to discriminate shades

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