progs/glsl/fragcoord.c

   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 <GL/glut.h>
  17 #include "shaderutil.h"
  18
  19
  20 static GLint WinWidth = 200, WinHeight = 200;
  21 static char *FragProgFile = NULL;
  22 static char *VertProgFile = NULL;
  23 static GLuint fragShader;
  24 static GLuint vertShader;
  25 static GLuint program;
  26 static GLint win = 0;
  27 static GLboolean Anim = GL_TRUE;
  28 static GLfloat PosX = 0.0, PosY = 0.0;
  29
  30
  31 static void
  32 Idle(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
  44 static void
  45 Redisplay(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
  67 static void
  68 Reshape(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
  83 static void
  84 CleanUp(void)
  85 {
  86    glDeleteShader(fragShader);
  87    glDeleteShader(vertShader);
  88    glDeleteProgram(program);
  89    glutDestroyWindow(win);
  90 }
  91
  92
  93 static void
  94 Key(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
 114 static void
 115 Init(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
 150 static void
 151 ParseOptions(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
 165 int
 166 main(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 }