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/gl.h>
  17 #include <GL/glut.h>
  18 #include <GL/glext.h>
  19 #include "extfuncs.h"
  20 #include "shaderutil.h"
  21
  22
  23 static GLint WinWidth = 200, WinHeight = 200;
  24 static char *FragProgFile = NULL;
  25 static char *VertProgFile = NULL;
  26 static GLuint fragShader;
  27 static GLuint vertShader;
  28 static GLuint program;
  29 static GLint win = 0;
  30 static GLboolean Anim = GL_TRUE;
  31 static GLfloat PosX = 0.0, PosY = 0.0;
  32
  33
  34 static void
  35 Idle(void)
  36 {
  37    float r = (WinWidth < WinHeight) ? WinWidth : WinHeight;
  38    float a = glutGet(GLUT_ELAPSED_TIME) * 0.001;
  39    r *= 0.25;
  40    PosX = WinWidth / 2 + r * cos(a);
  41    PosY = WinHeight / 2 + r * sin(a);
  42
  43    glutPostRedisplay();
  44 }
  45
  46
  47 static void
  48 Redisplay(void)
  49 {
  50    glClear(GL_COLOR_BUFFER_BIT);
  51
  52    glPushMatrix();
  53    glTranslatef(PosX, PosY, 0.0);
  54 #if 0
  55    glBegin(GL_POLYGON);
  56    glVertex2f(-50, -50);
  57    glVertex2f( 50, -50);
  58    glVertex2f( 50,  50);
  59    glVertex2f(-50,  50);
  60    glEnd();
  61 #else
  62    glutSolidSphere(50, 20, 10);
  63 #endif
  64    glPopMatrix();
  65
  66    glutSwapBuffers();
  67 }
  68
  69
  70 static void
  71 Reshape(int width, int height)
  72 {
  73    glViewport(0, 0, width, height);
  74    glMatrixMode(GL_PROJECTION);
  75    glLoadIdentity();
  76    glOrtho(0, width, 0, height, -55, 55);
  77
  78    glMatrixMode(GL_MODELVIEW);
  79    glLoadIdentity();
  80
  81    WinWidth = width;
  82    WinHeight = height;
  83 }
  84
  85
  86 static void
  87 CleanUp(void)
  88 {
  89    glDeleteShader_func(fragShader);
  90    glDeleteShader_func(vertShader);
  91    glDeleteProgram_func(program);
  92    glutDestroyWindow(win);
  93 }
  94
  95
  96 static void
  97 Key(unsigned char key, int x, int y)
  98 {
  99   (void) x;
 100   (void) y;
 101
 102    switch(key) {
 103    case ' ':
 104    case 'a':
 105       Anim = !Anim;
 106       glutIdleFunc(Anim ? Idle : NULL);
 107       break;
 108    case 27:
 109       CleanUp();
 110       exit(0);
 111       break;
 112    }
 113    glutPostRedisplay();
 114 }
 115
 116
 117 static void
 118 Init(void)
 119 {
 120    static const char *fragShaderText =
 121       "void main() { \n"
 122       "   vec4 scale = vec4(.005, 0.005, 0.5, 1.0);\n"
 123       "   gl_FragColor = gl_FragCoord * scale; \n"
 124       "}\n";
 125    static const char *vertShaderText =
 126       "void main() {\n"
 127       "   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
 128       "}\n";
 129
 130    if (!ShadersSupported())
 131       exit(1);
 132
 133    GetExtensionFuncs();
 134
 135    vertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
 136    fragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
 137    program = LinkShaders(vertShader, fragShader);
 138
 139    glUseProgram_func(program);
 140
 141    /*assert(glGetError() == 0);*/
 142
 143    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 144
 145    printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
 146
 147    assert(glIsProgram_func(program));
 148    assert(glIsShader_func(fragShader));
 149    assert(glIsShader_func(vertShader));
 150
 151    glColor3f(1, 0, 0);
 152 }
 153
 154
 155 static void
 156 ParseOptions(int argc, char *argv[])
 157 {
 158    int i;
 159    for (i = 1; i < argc; i++) {
 160       if (strcmp(argv[i], "-fs") == 0) {
 161          FragProgFile = argv[i+1];
 162       }
 163       else if (strcmp(argv[i], "-vs") == 0) {
 164          VertProgFile = argv[i+1];
 165       }
 166    }
 167 }
 168
 169
 170 int
 171 main(int argc, char *argv[])
 172 {
 173    glutInit(&argc, argv);
 174    glutInitWindowPosition( 0, 0);
 175    glutInitWindowSize(WinWidth, WinHeight);
 176    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
 177    win = glutCreateWindow(argv[0]);
 178    glewInit();
 179    glutReshapeFunc(Reshape);
 180    glutKeyboardFunc(Key);
 181    glutDisplayFunc(Redisplay);
 182    ParseOptions(argc, argv);
 183    Init();
 184    glutIdleFunc(Anim ? Idle : NULL);
 185    glutMainLoop();
 186    return 0;
 187 }