progs/glsl/vert-or-frag-only.c

   1 /**
   2  * Draw two quads, one using only a vertex shader, the other only with a
   3  * fragment shader.  They should appear the same.
   4  * 17 Dec 2008
   5  * Brian Paul
   6  */
   7
   8
   9 #include <assert.h>
  10 #include <string.h>
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <math.h>
  14 #include <GL/glew.h>
  15 #include <GL/glut.h>
  16 #include "shaderutil.h"
  17
  18
  19 static char *FragProgFile = NULL;
  20 static char *VertProgFile = NULL;
  21 static GLuint FragShader;
  22 static GLuint VertShader;
  23 static GLuint VertProgram;  /* w/out vertex shader */
  24 static GLuint FragProgram;  /* w/out fragment shader */
  25 static GLint Win = 0;
  26
  27
  28 static void
  29 DrawQuadColor(void)
  30 {
  31    glBegin(GL_QUADS);
  32    glColor3f(1, 0, 0);    glVertex2f(-1, -1);
  33    glColor3f(0, 1, 0);    glVertex2f( 1, -1);
  34    glColor3f(0, 0, 1);    glVertex2f( 1,  1);
  35    glColor3f(1, 0, 1);    glVertex2f(-1,  1);
  36    glEnd();
  37 }
  38
  39
  40 /** as above, but specify color via texcoords */
  41 static void
  42 DrawQuadTex(void)
  43 {
  44    glBegin(GL_QUADS);
  45    glTexCoord3f(1, 0, 0);    glVertex2f(-1, -1);
  46    glTexCoord3f(0, 1, 0);    glVertex2f( 1, -1);
  47    glTexCoord3f(0, 0, 1);    glVertex2f( 1,  1);
  48    glTexCoord3f(1, 0, 1);    glVertex2f(-1,  1);
  49    glEnd();
  50 }
  51
  52
  53 static void
  54 Redisplay(void)
  55 {
  56    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  57
  58    /* render with vertex shader only */
  59    glUseProgram(VertProgram);
  60    glPushMatrix();
  61    glTranslatef(-1.5, 0, 0);
  62    DrawQuadTex();
  63    glPopMatrix();
  64
  65    /* render with fragment shader only */
  66    glUseProgram(FragProgram);
  67    glPushMatrix();
  68    glTranslatef(+1.5, 0, 0);
  69    DrawQuadColor();
  70    glPopMatrix();
  71
  72    glutSwapBuffers();
  73 }
  74
  75
  76 static void
  77 Reshape(int width, int height)
  78 {
  79    glViewport(0, 0, width, height);
  80    glMatrixMode(GL_PROJECTION);
  81    glLoadIdentity();
  82    glOrtho(-4, 4, -2, 2, -1, 1);
  83    glMatrixMode(GL_MODELVIEW);
  84    glLoadIdentity();
  85 }
  86
  87
  88 static void
  89 CleanUp(void)
  90 {
  91    glDeleteShader(FragShader);
  92    glDeleteShader(VertShader);
  93    glDeleteProgram(VertProgram);
  94    glDeleteProgram(FragProgram);
  95    glutDestroyWindow(Win);
  96 }
  97
  98
  99 static void
 100 Key(unsigned char key, int x, int y)
 101 {
 102   (void) x;
 103   (void) y;
 104    switch(key) {
 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       "   gl_FragColor = gl_Color;\n"
 120       "}\n";
 121    static const char *vertShaderText =
 122       "void main() {\n"
 123       "   gl_Position = ftransform();\n"
 124       "   gl_FrontColor = gl_MultiTexCoord0;\n" /* see DrawQuadTex() */
 125       "}\n";
 126
 127    if (!ShadersSupported())
 128       exit(1);
 129
 130    if (FragProgFile)
 131       FragShader = CompileShaderFile(GL_FRAGMENT_SHADER, FragProgFile);
 132    else
 133       FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
 134
 135    if (VertProgFile)
 136       VertShader = CompileShaderFile(GL_VERTEX_SHADER, VertProgFile);
 137    else
 138       VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
 139
 140    VertProgram = LinkShaders(VertShader, 0);
 141    FragProgram = LinkShaders(0, FragShader);
 142
 143    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 144    glEnable(GL_DEPTH_TEST);
 145
 146    printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
 147
 148    assert(glIsProgram(VertProgram));
 149    assert(glIsProgram(FragProgram));
 150    assert(glIsShader(FragShader));
 151    assert(glIsShader(VertShader));
 152
 153    glColor3f(1, 0, 0);
 154 }
 155
 156
 157 static void
 158 ParseOptions(int argc, char *argv[])
 159 {
 160    int i;
 161    for (i = 1; i < argc; i++) {
 162       if (strcmp(argv[i], "-fs") == 0) {
 163          FragProgFile = argv[i+1];
 164       }
 165       else if (strcmp(argv[i], "-vs") == 0) {
 166          VertProgFile = argv[i+1];
 167       }
 168    }
 169 }
 170
 171
 172 int
 173 main(int argc, char *argv[])
 174 {
 175    glutInit(&argc, argv);
 176    glutInitWindowSize(400, 200);
 177    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 178    Win = glutCreateWindow(argv[0]);
 179    glewInit();
 180    glutReshapeFunc(Reshape);
 181    glutKeyboardFunc(Key);
 182    glutDisplayFunc(Redisplay);
 183    ParseOptions(argc, argv);
 184    Init();
 185    glutMainLoop();
 186    return 0;
 187 }