1/**
2 * Test GLSL gl_FragCoord fragment program attribute.
3 * Color the quad's fragments according to their window position.
4 *
5 * Brian Paul
6 * 20 Nov 2008
7 */
8
9
10#include <assert.h>
11#include <string.h>
12#include <stdio.h>
13#include <stdlib.h>
14#include <math.h>
15#include <GL/glew.h>
16#include "glut_wrap.h"
17#include "shaderutil.h"
18
19
20static GLint WinWidth = 200, WinHeight = 200;
21static char *FragProgFile = NULL;
22static char *VertProgFile = NULL;
23static GLuint fragShader;
24static GLuint vertShader;
25static GLuint program;
26static GLint win = 0;
27static GLboolean Anim = GL_TRUE;
28static GLfloat PosX = 0.0, PosY = 0.0;
29
30
31static void
32Idle(void)
33{
34   float r = (WinWidth < WinHeight) ? WinWidth : WinHeight;
35   float a = glutGet(GLUT_ELAPSED_TIME) * 0.001;
36   r *= 0.25;
37   PosX = WinWidth / 2 + r * cos(a);
38   PosY = WinHeight / 2 + r * sin(a);
39
40   glutPostRedisplay();
41}
42
43
44static void
45Redisplay(void)
46{
47   glClear(GL_COLOR_BUFFER_BIT);
48
49   glPushMatrix();
50   glTranslatef(PosX, PosY, 0.0);
51#if 0
52   glBegin(GL_POLYGON);
53   glVertex2f(-50, -50);
54   glVertex2f( 50, -50);
55   glVertex2f( 50,  50);
56   glVertex2f(-50,  50);
57   glEnd();
58#else
59   glutSolidSphere(50, 20, 10);
60#endif
61   glPopMatrix();
62
63   glutSwapBuffers();
64}
65
66
67static void
68Reshape(int width, int height)
69{
70   glViewport(0, 0, width, height);
71   glMatrixMode(GL_PROJECTION);
72   glLoadIdentity();
73   glOrtho(0, width, 0, height, -55, 55);
74
75   glMatrixMode(GL_MODELVIEW);
76   glLoadIdentity();
77
78   WinWidth = width;
79   WinHeight = height;
80}
81
82
83static void
84CleanUp(void)
85{
86   glDeleteShader(fragShader);
87   glDeleteShader(vertShader);
88   glDeleteProgram(program);
89   glutDestroyWindow(win);
90}
91
92
93static void
94Key(unsigned char key, int x, int y)
95{
96  (void) x;
97  (void) y;
98
99   switch(key) {
100   case ' ':
101   case 'a':
102      Anim = !Anim;
103      glutIdleFunc(Anim ? Idle : NULL);
104      break;
105   case 27:
106      CleanUp();
107      exit(0);
108      break;
109   }
110   glutPostRedisplay();
111}
112
113
114static void
115Init(void)
116{
117   static const char *fragShaderText =
118      "void main() { \n"
119      "   vec4 scale = vec4(.005, 0.005, 0.5, 1.0);\n"
120      "   gl_FragColor = gl_FragCoord * scale; \n"
121      "}\n";
122   static const char *vertShaderText =
123      "void main() {\n"
124      "   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
125      "}\n";
126
127   if (!ShadersSupported())
128      exit(1);
129
130   vertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
131   fragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
132   program = LinkShaders(vertShader, fragShader);
133
134   glUseProgram(program);
135
136   /*assert(glGetError() == 0);*/
137
138   glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
139
140   printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
141
142   assert(glIsProgram(program));
143   assert(glIsShader(fragShader));
144   assert(glIsShader(vertShader));
145
146   glColor3f(1, 0, 0);
147}
148
149
150static void
151ParseOptions(int argc, char *argv[])
152{
153   int i;
154   for (i = 1; i < argc; i++) {
155      if (strcmp(argv[i], "-fs") == 0) {
156         FragProgFile = argv[i+1];
157      }
158      else if (strcmp(argv[i], "-vs") == 0) {
159         VertProgFile = argv[i+1];
160      }
161   }
162}
163
164
165int
166main(int argc, char *argv[])
167{
168   glutInit(&argc, argv);
169   glutInitWindowSize(WinWidth, WinHeight);
170   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
171   win = glutCreateWindow(argv[0]);
172   glewInit();
173   glutReshapeFunc(Reshape);
174   glutKeyboardFunc(Key);
175   glutDisplayFunc(Redisplay);
176   ParseOptions(argc, argv);
177   Init();
178   glutIdleFunc(Anim ? Idle : NULL);
179   glutMainLoop();
180   return 0;
181}
182