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/gl.h>
  16 #include <GL/glut.h>
  17 #include <GL/glext.h>
  18 #include "extfuncs.h"
  19 #include "shaderutil.h"
  20
  21
  22 static char *FragProgFile = NULL;
  23 static char *VertProgFile = NULL;
  24 static GLuint FragShader;
  25 static GLuint VertShader;
  26 static GLuint VertProgram;  /* w/out vertex shader */
  27 static GLuint FragProgram;  /* w/out fragment shader */
  28 static GLint Win = 0;
  29
  30
  31 static void
  32 DrawQuadColor(void)
  33 {
  34    glBegin(GL_QUADS);
  35    glColor3f(1, 0, 0);    glVertex2f(-1, -1);
  36    glColor3f(0, 1, 0);    glVertex2f( 1, -1);
  37    glColor3f(0, 0, 1);    glVertex2f( 1,  1);
  38    glColor3f(1, 0, 1);    glVertex2f(-1,  1);
  39    glEnd();
  40 }
  41
  42
  43 /** as above, but specify color via texcoords */
  44 static void
  45 DrawQuadTex(void)
  46 {
  47    glBegin(GL_QUADS);
  48    glTexCoord3f(1, 0, 0);    glVertex2f(-1, -1);
  49    glTexCoord3f(0, 1, 0);    glVertex2f( 1, -1);
  50    glTexCoord3f(0, 0, 1);    glVertex2f( 1,  1);
  51    glTexCoord3f(1, 0, 1);    glVertex2f(-1,  1);
  52    glEnd();
  53 }
  54
  55
  56 static void
  57 Redisplay(void)
  58 {
  59    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  60
  61    /* render with vertex shader only */
  62    glUseProgram_func(VertProgram);
  63    glPushMatrix();
  64    glTranslatef(-1.5, 0, 0);
  65    DrawQuadTex();
  66    glPopMatrix();
  67
  68    /* render with fragment shader only */
  69    glUseProgram_func(FragProgram);
  70    glPushMatrix();
  71    glTranslatef(+1.5, 0, 0);
  72    DrawQuadColor();
  73    glPopMatrix();
  74
  75    glutSwapBuffers();
  76 }
  77
  78
  79 static void
  80 Reshape(int width, int height)
  81 {
  82    glViewport(0, 0, width, height);
  83    glMatrixMode(GL_PROJECTION);
  84    glLoadIdentity();
  85    glOrtho(-4, 4, -2, 2, -1, 1);
  86    glMatrixMode(GL_MODELVIEW);
  87    glLoadIdentity();
  88 }
  89
  90
  91 static void
  92 CleanUp(void)
  93 {
  94    glDeleteShader_func(FragShader);
  95    glDeleteShader_func(VertShader);
  96    glDeleteProgram_func(VertProgram);
  97    glDeleteProgram_func(FragProgram);
  98    glutDestroyWindow(Win);
  99 }
 100
 101
 102 static void
 103 Key(unsigned char key, int x, int y)
 104 {
 105   (void) x;
 106   (void) y;
 107    switch(key) {
 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       "   gl_FragColor = gl_Color;\n"
 123       "}\n";
 124    static const char *vertShaderText =
 125       "void main() {\n"
 126       "   gl_Position = ftransform();\n"
 127       "   gl_FrontColor = gl_MultiTexCoord0;\n" /* see DrawQuadTex() */
 128       "}\n";
 129
 130    if (!ShadersSupported())
 131       exit(1);
 132
 133    GetExtensionFuncs();
 134
 135    if (FragProgFile)
 136       FragShader = CompileShaderFile(GL_FRAGMENT_SHADER, FragProgFile);
 137    else
 138       FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
 139
 140    if (VertProgFile)
 141       VertShader = CompileShaderFile(GL_VERTEX_SHADER, VertProgFile);
 142    else
 143       VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
 144
 145    VertProgram = LinkShaders(VertShader, 0);
 146    FragProgram = LinkShaders(0, FragShader);
 147
 148    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 149    glEnable(GL_DEPTH_TEST);
 150
 151    printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
 152
 153    assert(glIsProgram_func(VertProgram));
 154    assert(glIsProgram_func(FragProgram));
 155    assert(glIsShader_func(FragShader));
 156    assert(glIsShader_func(VertShader));
 157
 158    glColor3f(1, 0, 0);
 159 }
 160
 161
 162 static void
 163 ParseOptions(int argc, char *argv[])
 164 {
 165    int i;
 166    for (i = 1; i < argc; i++) {
 167       if (strcmp(argv[i], "-fs") == 0) {
 168          FragProgFile = argv[i+1];
 169       }
 170       else if (strcmp(argv[i], "-vs") == 0) {
 171          VertProgFile = argv[i+1];
 172       }
 173    }
 174 }
 175
 176
 177 int
 178 main(int argc, char *argv[])
 179 {
 180    glutInit(&argc, argv);
 181    glutInitWindowPosition( 0, 0);
 182    glutInitWindowSize(400, 200);
 183    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 184    Win = glutCreateWindow(argv[0]);
 185    glewInit();
 186    glutReshapeFunc(Reshape);
 187    glutKeyboardFunc(Key);
 188    glutDisplayFunc(Redisplay);
 189    ParseOptions(argc, argv);
 190    Init();
 191    glutMainLoop();
 192    return 0;
 193 }