/* LetterL.c
 *
 * define display lists that draw the 3D letter L 
 */

#include <windows.h>
#include <stdio.h>

#include <GL/gl.h>

#define FLAT_L   1
#define SMOOTH_L 2

#define NPOINTS   12
#define NPOLYGONS 10

extern void getNormals();

void createDisplayLists() {

	int face, pt, pindex;

	/* Define the geometry */

	GLdouble point[NPOINTS][3] = 
	{{0.0, 0.0, 1.0},
	{2.0, 0.0, 1.0},
	{2.0, 1.0, 1.0},
	{1.0, 1.0, 1.0},
	{1.0, 3.0, 1.0},
	{0.0, 3.0, 1.0},
	{0.0, 0.0, 0.0},
	{2.0, 0.0, 0.0},
	{2.0, 1.0, 0.0},
	{1.0, 1.0, 0.0},
	{1.0, 3.0, 0.0},
	{0.0, 3.0, 0.0}};

	int polygon[NPOLYGONS][4] = 
	{{0, 1, 2, 3}, /* front faces */
	{0, 3, 4, 5},
	{9, 8, 7, 6}, /* back faces */
	{11, 10, 9, 6},
	{0, 5, 11, 6}, /* side faces */
	{1, 0, 6, 7},
	{2, 1, 7, 8},
	{3, 2, 8, 9},
	{4, 3, 9, 10},
	{5, 4, 10, 11}};

	/* Generate the normals for the letter */

	GLdouble face_normals[NPOLYGONS][3];
	GLdouble point_normals[NPOINTS][3];

	getNormals (point, NPOINTS, polygon, NPOLYGONS, face_normals, point_normals);

	/* Create a display list for flat shading */

	glNewList (FLAT_L, GL_COMPILE);
	for (face = 0; face < NPOLYGONS; face++) {
		glBegin(GL_POLYGON);
		glNormal3dv(face_normals[face]);
		for (pt = 0; pt < 4; pt++)  /* draw all points on the face */
			glVertex3dv (point[polygon[face][pt]]);
		glEnd();
	}
	glEndList();

	/* Create a display list for smooth shading */

	glNewList (SMOOTH_L, GL_COMPILE);
	for (face = 0; face < NPOLYGONS; face++) {
		glBegin(GL_POLYGON);
		for (pt = 0; pt < 4; pt++) { /* draw all points on the face */
			pindex = polygon[face][pt];
			glNormal3dv (point_normals[pindex]);
			glVertex3dv (point[pindex]);
		}
		glEnd();
	}
	glEndList();
}