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/gl.h>
  15 #include <GL/glut.h>
  16 #include <GL/glext.h>
  17 #include "extfuncs.h"
  18 #include "shaderutil.h"
  19
  20
  21 static char *FragProgFile = NULL;
  22 static char *VertProgFile = NULL;
  23 static GLuint FragShader;
  24 static GLuint VertShader;
  25 static GLuint VertProgram;  /* w/out vertex shader */
  26 static GLuint FragProgram;  /* w/out fragment shader */
  27 static GLint Win = 0;
  28
  29
  30 static void
  31 DrawQuadColor(void)
  32 {
  33    glBegin(GL_QUADS);
  34    glColor3f(1, 0, 0);    glVertex2f(-1, -1);
  35    glColor3f(0, 1, 0);    glVertex2f( 1, -1);
  36    glColor3f(0, 0, 1);    glVertex2f( 1,  1);
  37    glColor3f(1, 0, 1);    glVertex2f(-1,  1);
  38    glEnd();
  39 }
  40
  41
  42 /** as above, but specify color via texcoords */
  43 static void
  44 DrawQuadTex(void)
  45 {
  46    glBegin(GL_QUADS);
  47    glTexCoord3f(1, 0, 0);    glVertex2f(-1, -1);
  48    glTexCoord3f(0, 1, 0);    glVertex2f( 1, -1);
  49    glTexCoord3f(0, 0, 1);    glVertex2f( 1,  1);
  50    glTexCoord3f(1, 0, 1);    glVertex2f(-1,  1);
  51    glEnd();
  52 }
  53
  54
  55 static void
  56 Redisplay(void)
  57 {
  58    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  59
  60    /* render with vertex shader only */
  61    glUseProgram_func(VertProgram);
  62    glPushMatrix();
  63    glTranslatef(-1.5, 0, 0);
  64    DrawQuadTex();
  65    glPopMatrix();
  66
  67    /* render with fragment shader only */
  68    glUseProgram_func(FragProgram);
  69    glPushMatrix();
  70    glTranslatef(+1.5, 0, 0);
  71    DrawQuadColor();
  72    glPopMatrix();
  73
  74    glutSwapBuffers();
  75 }
  76
  77
  78 static void
  79 Reshape(int width, int height)
  80 {
  81    glViewport(0, 0, width, height);
  82    glMatrixMode(GL_PROJECTION);
  83    glLoadIdentity();
  84    glOrtho(-4, 4, -2, 2, -1, 1);
  85    glMatrixMode(GL_MODELVIEW);
  86    glLoadIdentity();
  87 }
  88
  89
  90 static void
  91 CleanUp(void)
  92 {
  93    glDeleteShader_func(FragShader);
  94    glDeleteShader_func(VertShader);
  95    glDeleteProgram_func(VertProgram);
  96    glDeleteProgram_func(FragProgram);
  97    glutDestroyWindow(Win);
  98 }
  99
 100
 101 static void
 102 Key(unsigned char key, int x, int y)
 103 {
 104   (void) x;
 105   (void) y;
 106    switch(key) {
 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       "   gl_FragColor = gl_Color;\n"
 122       "}\n";
 123    static const char *vertShaderText =
 124       "void main() {\n"
 125       "   gl_Position = ftransform();\n"
 126       "   gl_FrontColor = gl_MultiTexCoord0;\n" /* see DrawQuadTex() */
 127       "}\n";
 128
 129    if (!ShadersSupported())
 130       exit(1);
 131
 132    GetExtensionFuncs();
 133
 134    if (FragProgFile)
 135       FragShader = CompileShaderFile(GL_FRAGMENT_SHADER, FragProgFile);
 136    else
 137       FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
 138
 139    if (VertProgFile)
 140       VertShader = CompileShaderFile(GL_VERTEX_SHADER, VertProgFile);
 141    else
 142       VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
 143
 144    VertProgram = LinkShaders(VertShader, 0);
 145    FragProgram = LinkShaders(0, FragShader);
 146
 147    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 148    glEnable(GL_DEPTH_TEST);
 149
 150    printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
 151
 152    assert(glIsProgram_func(VertProgram));
 153    assert(glIsProgram_func(FragProgram));
 154    assert(glIsShader_func(FragShader));
 155    assert(glIsShader_func(VertShader));
 156
 157    glColor3f(1, 0, 0);
 158 }
 159
 160
 161 static void
 162 ParseOptions(int argc, char *argv[])
 163 {
 164    int i;
 165    for (i = 1; i < argc; i++) {
 166       if (strcmp(argv[i], "-fs") == 0) {
 167          FragProgFile = argv[i+1];
 168       }
 169       else if (strcmp(argv[i], "-vs") == 0) {
 170          VertProgFile = argv[i+1];
 171       }
 172    }
 173 }
 174
 175
 176 int
 177 main(int argc, char *argv[])
 178 {
 179    glutInit(&argc, argv);
 180    glutInitWindowPosition( 0, 0);
 181    glutInitWindowSize(400, 200);
 182    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 183    Win = glutCreateWindow(argv[0]);
 184    glutReshapeFunc(Reshape);
 185    glutKeyboardFunc(Key);
 186    glutDisplayFunc(Redisplay);
 187    ParseOptions(argc, argv);
 188    Init();
 189    glutMainLoop();
 190    return 0;
 191 }