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/*
* Exercise GL_EXT_secondary_color
*/
#define GL_GLEXT_PROTOTYPES
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
static int Width = 600;
static int Height = 200;
static GLfloat Near = 5.0, Far = 25.0;
static void Display( void )
{
GLfloat t;
glClearColor(0.2, 0.2, 0.8, 0);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
for (t = 0.0; t <= 1.0; t += 0.25) {
GLfloat x = t * 10.0 - 5.0;
GLfloat g = t;
/* top row: untextured */
glColor3f(1, 0, 0);
glPushMatrix();
glTranslatef(x, 1.2, 0);
#if defined(GL_EXT_secondary_color)
glSecondaryColor3fEXT(0, g, 0);
#endif
glBegin(GL_POLYGON);
glVertex2f(-1, -1);
glVertex2f( 1, -1);
glVertex2f( 1, 1);
glVertex2f(-1, 1);
glEnd();
glPopMatrix();
/* bottom row: textured */
glColor3f(1, 1, 1);
glEnable(GL_TEXTURE_2D);
glPushMatrix();
glTranslatef(x, -1.2, 0);
#if defined(GL_EXT_secondary_color)
glSecondaryColor3fEXT(0, g, 0);
#endif
glBegin(GL_POLYGON);
glTexCoord2f(0, 0); glVertex2f(-1, -1);
glTexCoord2f(1, 0); glVertex2f( 1, -1);
glTexCoord2f(1, 1); glVertex2f( 1, 1);
glTexCoord2f(0, 1); glVertex2f(-1, 1);
glEnd();
glPopMatrix();
glDisable(GL_TEXTURE_2D);
}
glutSwapBuffers();
}
static void Reshape( int width, int height )
{
GLfloat ar = (float) width / (float) height;
Width = width;
Height = height;
glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glFrustum( -ar, ar, -1.0, 1.0, Near, Far );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glTranslatef( 0.0, 0.0, -15.0 );
}
static void Key( unsigned char key, int x, int y )
{
(void) x;
(void) y;
switch (key) {
case 27:
exit(0);
break;
}
glutPostRedisplay();
}
static void Init( void )
{
GLubyte image[4*4][3];
GLint i;
if (!glutExtensionSupported("GL_EXT_secondary_color")) {
printf("Sorry, this program requires GL_EXT_secondary_color\n");
exit(1);
}
/* setup red texture with one back texel */
for (i = 0; i < 4*4; i++) {
if (i == 0) {
image[i][0] = 0;
image[i][1] = 0;
image[i][2] = 0;
}
else {
image[i][0] = 255;
image[i][1] = 0;
image[i][2] = 0;
}
}
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 4, 4, 0,
GL_RGB, GL_UNSIGNED_BYTE, image);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
#if defined(GL_EXT_secondary_color)
glEnable(GL_COLOR_SUM_EXT);
#endif
glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SEPARATE_SPECULAR_COLOR);
printf("Squares should be colored from red -> orange -> yellow.\n");
printf("Top row is untextured.\n");
printf("Bottom row is textured (red texture with one black texel).\n");
printf("Rows should be identical, except for lower-left texel.\n");
}
int main( int argc, char *argv[] )
{
glutInit( &argc, argv );
glutInitWindowPosition( 0, 0 );
glutInitWindowSize( Width, Height );
glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
glutCreateWindow(argv[0]);
glutReshapeFunc( Reshape );
glutKeyboardFunc( Key );
glutDisplayFunc( Display );
Init();
glutMainLoop();
return 0;
}
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