progs/trivial/fs-tri.c

   1 /* Test fragment shader */
   2
   3 #include <assert.h>
   4 #include <string.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <math.h>
   8 #include <GL/glew.h>
   9 #include <GL/glut.h>
  10
  11
  12 static GLuint fragShader;
  13 static GLuint vertShader;
  14 static GLuint program;
  15 static GLint win = 0;
  16 static GLfloat xpos = 0, ypos = 0;
  17
  18
  19 static void
  20 Redisplay(void)
  21 {
  22    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  23
  24    glPushMatrix();
  25    glTranslatef(xpos, ypos, 0);
  26
  27    glBegin(GL_TRIANGLES);
  28    glColor3f(1, 0, 0);
  29    glVertex2f(-0.9, -0.9);
  30    glColor3f(0, 1, 0);
  31    glVertex2f( 0.9, -0.9);
  32    glColor3f(0, 0, 1);
  33    glVertex2f( 0,  0.9);
  34    glEnd();
  35
  36    glPopMatrix();
  37
  38    glutSwapBuffers();
  39 }
  40
  41
  42 static void
  43 Reshape(int width, int height)
  44 {
  45    glViewport(0, 0, width, height);
  46    glMatrixMode(GL_PROJECTION);
  47    glLoadIdentity();
  48    glOrtho(-1, 1, -1, 1, -1, 1);
  49    glMatrixMode(GL_MODELVIEW);
  50    glLoadIdentity();
  51 }
  52
  53
  54 static void
  55 CleanUp(void)
  56 {
  57    glDeleteShader(fragShader);
  58    glDeleteShader(vertShader);
  59    glDeleteProgram(program);
  60    glutDestroyWindow(win);
  61 }
  62
  63
  64 static void
  65 Key(unsigned char key, int x, int y)
  66 {
  67   (void) x;
  68   (void) y;
  69
  70    switch(key) {
  71    case 27:
  72       CleanUp();
  73       exit(0);
  74       break;
  75    }
  76    glutPostRedisplay();
  77 }
  78
  79
  80 static void
  81 SpecialKey(int key, int x, int y)
  82 {
  83    const GLfloat step = 0.1;
  84
  85   (void) x;
  86   (void) y;
  87
  88    switch(key) {
  89    case GLUT_KEY_UP:
  90       ypos += step;
  91       break;
  92    case GLUT_KEY_DOWN:
  93       ypos -= step;
  94       break;
  95    case GLUT_KEY_LEFT:
  96       xpos -= step;
  97       break;
  98    case GLUT_KEY_RIGHT:
  99       xpos += step;
 100       break;
 101    }
 102    glutPostRedisplay();
 103 }
 104
 105
 106 static void
 107 LoadAndCompileShader(GLuint shader, const char *text)
 108 {
 109    GLint stat;
 110
 111    glShaderSource(shader, 1, (const GLchar **) &text, NULL);
 112
 113    glCompileShader(shader);
 114
 115    glGetShaderiv(shader, GL_COMPILE_STATUS, &stat);
 116    if (!stat) {
 117       GLchar log[1000];
 118       GLsizei len;
 119       glGetShaderInfoLog(shader, 1000, &len, log);
 120       fprintf(stderr, "fslight: problem compiling shader:\n%s\n", log);
 121       exit(1);
 122    }
 123 }
 124
 125
 126 static void
 127 CheckLink(GLuint prog)
 128 {
 129    GLint stat;
 130    glGetProgramiv(prog, GL_LINK_STATUS, &stat);
 131    if (!stat) {
 132       GLchar log[1000];
 133       GLsizei len;
 134       glGetProgramInfoLog(prog, 1000, &len, log);
 135       fprintf(stderr, "Linker error:\n%s\n", log);
 136    }
 137 }
 138
 139
 140 static void
 141 Init(void)
 142 {
 143    /* fragment color is a function of fragment position: */
 144    static const char *fragShaderText =
 145       "void main() {\n"
 146       "   gl_FragColor = gl_FragCoord * vec4(0.005); \n"
 147       "   //gl_FragColor = gl_Color; \n"
 148       "   //gl_FragColor = vec4(1, 0, 0.5, 0); \n"
 149       "}\n";
 150 #if 0
 151    static const char *vertShaderText =
 152       "varying vec3 normal;\n"
 153       "void main() {\n"
 154       "   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
 155       "   normal = gl_NormalMatrix * gl_Normal;\n"
 156       "}\n";
 157 #endif
 158    const char *version;
 159
 160    version = (const char *) glGetString(GL_VERSION);
 161    if (version[0] != '2' || version[1] != '.') {
 162       printf("This program requires OpenGL 2.x, found %s\n", version);
 163       exit(1);
 164    }
 165
 166    fragShader = glCreateShader(GL_FRAGMENT_SHADER);
 167    LoadAndCompileShader(fragShader, fragShaderText);
 168
 169 #if 0
 170    vertShader = glCreateShader(GL_VERTEX_SHADER);
 171    LoadAndCompileShader(vertShader, vertShaderText);
 172 #endif
 173
 174    program = glCreateProgram();
 175    glAttachShader(program, fragShader);
 176 #if 0
 177    glAttachShader(program, vertShader);
 178 #endif
 179    glLinkProgram(program);
 180    CheckLink(program);
 181    glUseProgram(program);
 182
 183    assert(glGetError() == 0);
 184
 185    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 186
 187    printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
 188 }
 189
 190
 191 int
 192 main(int argc, char *argv[])
 193 {
 194    glutInit(&argc, argv);
 195    glutInitWindowPosition( 0, 0);
 196    glutInitWindowSize(200, 200);
 197    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 198    win = glutCreateWindow(argv[0]);
 199    glewInit();
 200    glutReshapeFunc(Reshape);
 201    glutKeyboardFunc(Key);
 202    glutSpecialFunc(SpecialKey);
 203    glutDisplayFunc(Redisplay);
 204    Init();
 205    glutMainLoop();
 206    return 0;
 207 }
 208
 209