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/gl.h>
  16 #include <GL/glut.h>
  17 #include <GL/glext.h>
  18 #include "extfuncs.h"
  19 #include "shaderutil.h"
  20
  21
  22 static GLint WinWidth = 200, WinHeight = 200;
  23 static char *FragProgFile = NULL;
  24 static char *VertProgFile = NULL;
  25 static GLuint fragShader;
  26 static GLuint vertShader;
  27 static GLuint program;
  28 static GLint win = 0;
  29 static GLboolean Anim = GL_TRUE;
  30 static GLfloat PosX = 0.0, PosY = 0.0;
  31
  32
  33 static void
  34 Idle(void)
  35 {
  36    float r = (WinWidth < WinHeight) ? WinWidth : WinHeight;
  37    float a = glutGet(GLUT_ELAPSED_TIME) * 0.001;
  38    r *= 0.25;
  39    PosX = WinWidth / 2 + r * cos(a);
  40    PosY = WinHeight / 2 + r * sin(a);
  41
  42    glutPostRedisplay();
  43 }
  44
  45
  46 static void
  47 Redisplay(void)
  48 {
  49    glClear(GL_COLOR_BUFFER_BIT);
  50
  51    glPushMatrix();
  52    glTranslatef(PosX, PosY, 0.0);
  53 #if 0
  54    glBegin(GL_POLYGON);
  55    glVertex2f(-50, -50);
  56    glVertex2f( 50, -50);
  57    glVertex2f( 50,  50);
  58    glVertex2f(-50,  50);
  59    glEnd();
  60 #else
  61    glutSolidSphere(50, 20, 10);
  62 #endif
  63    glPopMatrix();
  64
  65    glutSwapBuffers();
  66 }
  67
  68
  69 static void
  70 Reshape(int width, int height)
  71 {
  72    glViewport(0, 0, width, height);
  73    glMatrixMode(GL_PROJECTION);
  74    glLoadIdentity();
  75    glOrtho(0, width, 0, height, -55, 55);
  76
  77    glMatrixMode(GL_MODELVIEW);
  78    glLoadIdentity();
  79
  80    WinWidth = width;
  81    WinHeight = height;
  82 }
  83
  84
  85 static void
  86 CleanUp(void)
  87 {
  88    glDeleteShader_func(fragShader);
  89    glDeleteShader_func(vertShader);
  90    glDeleteProgram_func(program);
  91    glutDestroyWindow(win);
  92 }
  93
  94
  95 static void
  96 Key(unsigned char key, int x, int y)
  97 {
  98   (void) x;
  99   (void) y;
 100
 101    switch(key) {
 102    case ' ':
 103    case 'a':
 104       Anim = !Anim;
 105       glutIdleFunc(Anim ? Idle : NULL);
 106       break;
 107    case 27:
 108       CleanUp();
 109       exit(0);
 110       break;
 111    }
 112    glutPostRedisplay();
 113 }
 114
 115
 116 static void
 117 Init(void)
 118 {
 119    static const char *fragShaderText =
 120       "void main() { \n"
 121       "   vec4 scale = vec4(.005, 0.005, 0.5, 1.0);\n"
 122       "   gl_FragColor = gl_FragCoord * scale; \n"
 123       "}\n";
 124    static const char *vertShaderText =
 125       "void main() {\n"
 126       "   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
 127       "}\n";
 128
 129    if (!ShadersSupported())
 130       exit(1);
 131
 132    GetExtensionFuncs();
 133
 134    vertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
 135    fragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
 136    program = LinkShaders(vertShader, fragShader);
 137
 138    glUseProgram_func(program);
 139
 140    /*assert(glGetError() == 0);*/
 141
 142    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 143
 144    printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
 145
 146    assert(glIsProgram_func(program));
 147    assert(glIsShader_func(fragShader));
 148    assert(glIsShader_func(vertShader));
 149
 150    glColor3f(1, 0, 0);
 151 }
 152
 153
 154 static void
 155 ParseOptions(int argc, char *argv[])
 156 {
 157    int i;
 158    for (i = 1; i < argc; i++) {
 159       if (strcmp(argv[i], "-fs") == 0) {
 160          FragProgFile = argv[i+1];
 161       }
 162       else if (strcmp(argv[i], "-vs") == 0) {
 163          VertProgFile = argv[i+1];
 164       }
 165    }
 166 }
 167
 168
 169 int
 170 main(int argc, char *argv[])
 171 {
 172    glutInit(&argc, argv);
 173    glutInitWindowPosition( 0, 0);
 174    glutInitWindowSize(WinWidth, WinHeight);
 175    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
 176    win = glutCreateWindow(argv[0]);
 177    glutReshapeFunc(Reshape);
 178    glutKeyboardFunc(Key);
 179    glutDisplayFunc(Redisplay);
 180    ParseOptions(argc, argv);
 181    Init();
 182    glutIdleFunc(Anim ? Idle : NULL);
 183    glutMainLoop();
 184    return 0;
 185 }