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/*
* Test glMapBuffer() call immediately after glDrawArrays().
* See details below.
*
* NOTE: Do not use freeglut with this test! It calls the Display()
* callback twice right away instead of just once.
*
* Brian Paul
* 27 Feb 2009
*/
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <GL/glut.h>
static GLuint BufferID;
static GLuint Win;
/*
* Create VBO (position and color) and load with data.
*/
static void
SetupBuffers(void)
{
static const GLfloat data[] = {
/* vertex */ /* color */
0, -1, 0, 1, 1, 0,
1, 0, 0, 1, 1, 0,
0, 1, 0, 1, 1, 0,
-1, 0, 0, 1, 1, 0
};
glGenBuffersARB(1, &BufferID);
glBindBufferARB(GL_ARRAY_BUFFER_ARB, BufferID);
glBufferDataARB(GL_ARRAY_BUFFER_ARB, sizeof(data), data,
GL_STATIC_DRAW_ARB);
}
static void
Draw(void)
{
static int count = 1;
printf("Draw Frame %d\n", count);
count++;
glBindBufferARB(GL_ARRAY_BUFFER_ARB, BufferID);
glVertexPointer(3, GL_FLOAT, 24, 0);
glEnable(GL_VERTEX_ARRAY);
glColorPointer(3, GL_FLOAT, 24, (void*) 12);
glEnable(GL_COLOR_ARRAY);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
if (0)
glFinish();
/* Immediately map the color buffer and change something.
* This should not effect the first glDrawArrays above, but the
* next time we draw we should see a black vertex.
*/
if (1) {
GLfloat *m = (GLfloat *) glMapBufferARB(GL_ARRAY_BUFFER_ARB,
GL_WRITE_ONLY_ARB);
m[3] = m[4] = m[5] = 0.0f; /* black vertex */
glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);
}
}
static void Display( void )
{
glClear( GL_COLOR_BUFFER_BIT );
Draw();
glutSwapBuffers();
}
static void Reshape( int width, int height )
{
float ar = (float) width / (float) height;
glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glFrustum( -ar, ar, -1.0, 1.0, 5.0, 25.0 );
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;
if (key == 27) {
glutDestroyWindow(Win);
exit(0);
}
glutPostRedisplay();
}
static void Init( void )
{
if (!glutExtensionSupported("GL_ARB_vertex_buffer_object")) {
printf("GL_ARB_vertex_buffer_object not found!\n");
exit(0);
}
printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
SetupBuffers();
}
int main( int argc, char *argv[] )
{
glutInit( &argc, argv );
glutInitWindowPosition( 0, 0 );
glutInitWindowSize( 300, 300 );
glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
Win = glutCreateWindow(argv[0]);
glewInit();
glutReshapeFunc( Reshape );
glutKeyboardFunc( Key );
glutDisplayFunc( Display );
Init();
glutMainLoop();
return 0;
}
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