quads.c revision 32001f49 
1/**
2 * Draw colored quads.
3 */
4
5
6#include <stdio.h>
7#include <stdlib.h>
8#include <math.h>
9#include <GL/glew.h>
10#include "glut_wrap.h"
11
12#define NUM_QUADS 20
13
14
15static int Win;
16static GLfloat Xrot = 40, Yrot = 0, Zrot = 0;
17static GLboolean Anim = GL_TRUE;
18static GLuint Vbuffer = 0;
19
20#if 1
21#else
22static GLfloat buf[NUM_QUADS * 6 * 4];
23#endif
24
25static GLboolean doSwapBuffers = GL_TRUE;
26
27static GLint Frames = 0, T0 = 0;
28
29
30static void
31Idle(void)
32{
33   Xrot += 3.0;
34   Yrot += 4.0;
35   Zrot += 2.0;
36   glutPostRedisplay();
37}
38
39
40static void
41Draw(void)
42{
43   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
44
45   glPushMatrix();
46   glRotatef(Xrot, 1, 0, 0);
47   glRotatef(Yrot, 0, 1, 0);
48   glRotatef(Zrot, 0, 0, 1);
49
50   glDrawArrays(GL_QUADS, 0, NUM_QUADS*4);
51
52   glPopMatrix();
53
54   if (doSwapBuffers)
55      glutSwapBuffers();
56   /*
57   else
58      glFinish();
59   */
60
61   {
62      GLint t = glutGet(GLUT_ELAPSED_TIME);
63      Frames++;
64      if (t - T0 >= 5000) {
65         GLfloat seconds = (t - T0) / 1000.0;
66         GLfloat fps = Frames / seconds;
67         printf("%d frames in %6.3f seconds = %6.3f FPS\n",
68                Frames, seconds, fps);
69         T0 = t;
70         Frames = 0;
71      }
72   }
73}
74
75
76static void
77Reshape(int width, int height)
78{
79   glViewport(0, 0, width, height);
80   glMatrixMode(GL_PROJECTION);
81   glLoadIdentity();
82   glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
83   glMatrixMode(GL_MODELVIEW);
84   glLoadIdentity();
85   glTranslatef(0.0, 0.0, -8.0);
86}
87
88
89static void
90Key(unsigned char key, int x, int y)
91{
92   const GLfloat step = 3.0;
93   (void) x;
94   (void) y;
95   switch (key) {
96      case 's':
97         doSwapBuffers = !doSwapBuffers;
98         break;
99      case 'a':
100         Anim = !Anim;
101         if (Anim)
102            glutIdleFunc(Idle);
103         else
104            glutIdleFunc(NULL);
105         break;
106      case 'z':
107         Zrot -= step;
108         break;
109      case 'Z':
110         Zrot += step;
111         break;
112      case 27:
113         glutDestroyWindow(Win);
114         exit(0);
115         break;
116   }
117   glutPostRedisplay();
118}
119
120
121static void
122SpecialKey(int key, int x, int y)
123{
124   const GLfloat step = 3.0;
125   (void) x;
126   (void) y;
127   switch (key) {
128      case GLUT_KEY_UP:
129         Xrot -= step;
130         break;
131      case GLUT_KEY_DOWN:
132         Xrot += step;
133         break;
134      case GLUT_KEY_LEFT:
135         Yrot -= step;
136         break;
137      case GLUT_KEY_RIGHT:
138         Yrot += step;
139         break;
140   }
141   glutPostRedisplay();
142}
143
144
145static void
146quad(float x, float y, float z, float *v)
147{
148   int k = 0;
149
150   /* color */
151   v[k++] = x * 0.5 + 0.5;
152   v[k++] = y * 0.5 + 0.5;
153   v[k++] = z * 0.5 + 0.5;
154   /* vert */
155   v[k++] = x;
156   v[k++] = y;
157   v[k++] = z;
158
159   /* color */
160   v[k++] = -x * 0.5 + 0.5;
161   v[k++] = -y * 0.5 + 0.5;
162   v[k++] = z * 0.5 + 0.5;
163   /* vert */
164   v[k++] = -x;
165   v[k++] = -y;
166   v[k++] = z;
167
168   /* color */
169   v[k++] = -x * 0.5 + 0.5;
170   v[k++] = -y * 0.5 + 0.5;
171   v[k++] = -z * 0.5 + 0.5;
172   /* vert */
173   v[k++] = -x;
174   v[k++] = -y;
175   v[k++] = -z;
176
177   /* color */
178   v[k++] = x * 0.5 + 0.5;
179   v[k++] = y * 0.5 + 0.5;
180   v[k++] = -z * 0.5 + 0.5;
181   /* vert */
182   v[k++] = x;
183   v[k++] = y;
184   v[k++] = -z;
185}
186
187static void
188gen_quads(GLfloat *buf)
189{
190   float *v = buf;
191   float r = 1.0;
192   int i;
193
194   for (i = 0; i < NUM_QUADS; i++) {
195      float angle = i / (float) NUM_QUADS * M_PI;
196      float x = r * cos(angle);
197      float y = r * sin(angle);
198      float z = 1.10;
199      quad(x, y, z, v);
200      v += 24;
201   }
202
203   if (0) {
204      float *p = buf;
205      for (i = 0; i < NUM_QUADS * 4 * 2; i++) {
206         printf("%d: %f %f %f\n", i, p[0], p[1], p[2]);
207         p += 3;
208      }
209   }
210}
211
212
213static void
214Init(void)
215{
216   int bytes = NUM_QUADS * 4 * 2 * 3 * sizeof(float);
217   GLfloat *f;
218
219#if 1
220   glGenBuffers(1, &Vbuffer);
221   glBindBuffer(GL_ARRAY_BUFFER, Vbuffer);
222   glBufferData(GL_ARRAY_BUFFER_ARB, bytes, NULL, GL_STATIC_DRAW_ARB);
223   f = (float *) glMapBuffer(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);
224   gen_quads(f);
225   glUnmapBuffer(GL_ARRAY_BUFFER_ARB);
226   glColorPointer(3, GL_FLOAT, 6*sizeof(float), (void *) 0);
227   glVertexPointer(3, GL_FLOAT, 6*sizeof(float), (void *) 12);
228#else
229   f = buf;
230   gen_quads(f);
231   glColorPointer(3, GL_FLOAT, 6*sizeof(float), buf);
232   glVertexPointer(3, GL_FLOAT, 6*sizeof(float), buf + 3);
233#endif
234
235   glEnableClientState(GL_COLOR_ARRAY);
236   glEnableClientState(GL_VERTEX_ARRAY);
237
238   glEnable(GL_DEPTH_TEST);
239
240   glClearColor(0.5, 0.5, 0.5, 0.0);
241}
242
243
244int
245main(int argc, char *argv[])
246{
247   glutInit(&argc, argv);
248   glutInitWindowPosition(0, 0);
249   glutInitWindowSize(600, 600);
250   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
251   Win = glutCreateWindow(argv[0]);
252   glewInit();
253   glutReshapeFunc(Reshape);
254   glutKeyboardFunc(Key);
255   glutSpecialFunc(SpecialKey);
256   glutDisplayFunc(Draw);
257   if (Anim)
258      glutIdleFunc(Idle);
259   Init();
260   glutMainLoop();
261   return 0;
262}
263