src/tests/blendminmax.c

   1 /*
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  14  * Software.
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  24
  25 /**
  26  * \file blendminmax.c
  27  *
  28  * Simple test of GL_EXT_blend_minmax functionality.  Four squares are drawn
  29  * with different blending modes, but all should be rendered with the same
  30  * final color.
  31  *
  32  * \author Ian Romanick <idr@us.ibm.com>
  33  */
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <GL/glut.h>
  38
  39 static int Width = 400;
  40 static int Height = 200;
  41 static const GLfloat Near = 5.0, Far = 25.0;
  42
  43
  44 static void Display( void )
  45 {
  46    glClearColor(0.2, 0.2, 0.8, 0);
  47    glClear( GL_COLOR_BUFFER_BIT );
  48
  49    glPushMatrix();
  50
  51    /* This is the "reference" square.
  52     */
  53
  54    glTranslatef(-4.5, 0, 0);
  55    glBlendEquation( GL_FUNC_ADD );
  56    glBlendFunc( GL_ONE, GL_ZERO );
  57    glBegin(GL_QUADS);
  58    glColor3f( 0.5, 0.5, 0.5 );
  59    glVertex2f(-1, -1);
  60    glVertex2f( 1, -1);
  61    glVertex2f( 1,  1);
  62    glVertex2f(-1,  1);
  63    glEnd();
  64
  65
  66    /* GL_MIN and GL_MAX are supposed to ignore the blend function setting.
  67     * To test that, we set the blend function to GL_ZERO for both color and
  68     * alpha each time GL_MIN or GL_MAX is used.
  69     *
  70     * Apple ships an extension called GL_ATI_blend_weighted_minmax (supported
  71     * on Mac OS X 10.2 and later).  I believe the difference with that
  72     * extension is that it uses the blend function.  However, I have no idea
  73     * what the enums are for it.  The extension is listed at Apple's developer
  74     * site, but there is no documentation.
  75     *
  76     * http://developer.apple.com/opengl/extensions.html
  77     */
  78
  79    glTranslatef(3.0, 0, 0);
  80    glBlendEquation( GL_FUNC_ADD );
  81    glBlendFunc( GL_ONE, GL_ZERO );
  82    glBegin(GL_QUADS);
  83    glColor3f( 0.5, 0.5, 0.5 );
  84    glVertex2f(-1, -1);
  85    glVertex2f( 1, -1);
  86    glVertex2f( 1,  1);
  87    glVertex2f(-1,  1);
  88    glEnd();
  89
  90    glBlendEquation( GL_MAX );
  91    glBlendFunc( GL_ZERO, GL_ZERO );
  92    glBegin(GL_QUADS);
  93    glColor3f( 0.2, 0.2, 0.2 );
  94    glVertex2f(-1, -1);
  95    glVertex2f( 1, -1);
  96    glVertex2f( 1,  1);
  97    glVertex2f(-1,  1);
  98    glEnd();
  99
 100
 101    glTranslatef(3.0, 0, 0);
 102    glBlendEquation( GL_FUNC_ADD );
 103    glBlendFunc( GL_ONE, GL_ZERO );
 104    glBegin(GL_QUADS);
 105    glColor3f( 0.5, 0.5, 0.5 );
 106    glVertex2f(-1, -1);
 107    glVertex2f( 1, -1);
 108    glVertex2f( 1,  1);
 109    glVertex2f(-1,  1);
 110    glEnd();
 111
 112    glBlendEquation( GL_MIN );
 113    glBlendFunc( GL_ZERO, GL_ZERO );
 114    glBegin(GL_QUADS);
 115    glColor3f( 0.8, 0.8, 0.8 );
 116    glVertex2f(-1, -1);
 117    glVertex2f( 1, -1);
 118    glVertex2f( 1,  1);
 119    glVertex2f(-1,  1);
 120    glEnd();
 121
 122
 123    glTranslatef(3.0, 0, 0);
 124    glBlendEquation( GL_FUNC_ADD );
 125    glBlendFunc( GL_ONE, GL_ZERO );
 126    glBegin(GL_QUADS);
 127    glColor3f( 0.8, 0.8, 0.8 );
 128    glVertex2f(-1, -1);
 129    glVertex2f( 1, -1);
 130    glVertex2f( 1,  1);
 131    glVertex2f(-1,  1);
 132    glEnd();
 133
 134    glBlendEquation( GL_MIN );
 135    glBlendFunc( GL_ZERO, GL_ZERO );
 136    glBegin(GL_QUADS);
 137    glColor3f( 0.5, 0.5, 0.5 );
 138    glVertex2f(-1, -1);
 139    glVertex2f( 1, -1);
 140    glVertex2f( 1,  1);
 141    glVertex2f(-1,  1);
 142    glEnd();
 143
 144    glPopMatrix();
 145
 146    glutSwapBuffers();
 147 }
 148
 149
 150 static void Reshape( int width, int height )
 151 {
 152    GLfloat ar = (float) width / (float) height;
 153    Width = width;
 154    Height = height;
 155    glViewport( 0, 0, width, height );
 156    glMatrixMode( GL_PROJECTION );
 157    glLoadIdentity();
 158    glFrustum( -ar, ar, -1.0, 1.0, Near, Far );
 159    glMatrixMode( GL_MODELVIEW );
 160    glLoadIdentity();
 161    glTranslatef( 0.0, 0.0, -15.0 );
 162 }
 163
 164
 165 static void Key( unsigned char key, int x, int y )
 166 {
 167    (void) x;
 168    (void) y;
 169    switch (key) {
 170       case 27:
 171          exit(0);
 172          break;
 173    }
 174    glutPostRedisplay();
 175 }
 176
 177
 178 static void Init( void )
 179 {
 180    const char * const ver_string = (const char * const)
 181        glGetString( GL_VERSION );
 182
 183    printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
 184    printf("GL_VERSION = %s\n", ver_string);
 185
 186    if ( !glutExtensionSupported("GL_ARB_imaging") && !glutExtensionSupported("GL_EXT_blend_minmax")) {
 187       printf("Sorry, this program requires either GL_ARB_imaging or GL_EXT_blend_minmax.\n");
 188       exit(1);
 189    }
 190
 191    printf("\nAll 4 squares should be the same color.\n");
 192    glEnable( GL_BLEND );
 193 }
 194
 195
 196 int main( int argc, char *argv[] )
 197 {
 198    glutInit( &argc, argv );
 199    glutInitWindowPosition( 0, 0 );
 200    glutInitWindowSize( Width, Height );
 201    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
 202    glutCreateWindow( "GL_EXT_blend_minmax test" );
 203    glutReshapeFunc( Reshape );
 204    glutKeyboardFunc( Key );
 205    glutDisplayFunc( Display );
 206    Init();
 207    glutMainLoop();
 208    return 0;
 209 }