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/*
* Test glMapBuffer() and glMapBufferRange()
*
* Fill a VBO with vertex data to draw several colored quads.
* On each redraw, update the geometry for just one rect in the VBO.
*
* Brian Paul
* 4 March 2009
*/
#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/glew.h>
#include <GL/glew.h>
#include <GL/glut.h>
static GLuint Win;
static const GLuint NumRects = 10;
static GLuint BufferID;
static GLboolean Anim = GL_TRUE;
static GLboolean UseBufferRange = GL_FALSE;
static const float RectData[] = {
/* vertex */ /* color */
0, -1, 0, 1, 0, 0,
1, 0, 0, 1, 1, 0,
0, 1, 0, 0, 1, 1,
-1, 0, 0, 1, 0, 1
};
/**
* The buffer contains vertex positions (float[3]) and colors (float[3])
* for 'NumRects' quads.
* This function updates/rotates one quad in the buffer.
*/
static void
UpdateRect(int r, float angle)
{
float *rect;
int i;
assert(r < NumRects);
glBindBufferARB(GL_ARRAY_BUFFER_ARB, BufferID);
if (UseBufferRange) {
GLintptr offset = r * sizeof(RectData);
GLsizeiptr length = sizeof(RectData);
GLbitfield access = GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_RANGE_BIT;
float *buf = (float *) glMapBufferRange(GL_ARRAY_BUFFER_ARB,
offset, length, access);
rect = buf;
}
else {
/* map whole buffer */
float *buf = (float *)
glMapBufferARB(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);
rect = buf + r * 24;
}
/* set rect verts/colors */
memcpy(rect, RectData, sizeof(RectData));
/* loop over four verts, updating vertices */
for (i = 0; i < 4; i++) {
float x = 0.2 * RectData[i*6+0];
float y = 0.2 * RectData[i*6+1];
float xpos = -2.5 + 0.5 * r;
float ypos = 0.0;
/* translate and rotate vert */
rect[i * 6 + 0] = xpos + x * cos(angle) + y * sin(angle);
rect[i * 6 + 1] = ypos + x * sin(angle) - y * cos(angle);
}
glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);
}
static void
LoadBuffer(void)
{
static int frame = 0;
float angle = glutGet(GLUT_ELAPSED_TIME) * 0.001;
UpdateRect(frame % NumRects, angle);
frame++;
}
static void
Draw(void)
{
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_QUADS, 0, NumRects * 4);
if (0)
glFinish();
}
static void
Display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
Draw();
glutSwapBuffers();
}
static void
Reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-3.0, 3.0, -1.0, 1.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
static void
Idle(void)
{
LoadBuffer();
glutPostRedisplay();
}
static void
Key(unsigned char key, int x, int y)
{
(void) x;
(void) y;
if (key == 'a') {
Anim = !Anim;
glutIdleFunc(Anim ? Idle : NULL);
}
else if (key == 's') {
LoadBuffer();
}
else if (key == 27) {
glutDestroyWindow(Win);
exit(0);
}
glutPostRedisplay();
}
static void
Init(void)
{
GLuint BufferSize = NumRects * sizeof(RectData);
float *buf;
if (!glutExtensionSupported("GL_ARB_vertex_buffer_object")) {
printf("GL_ARB_vertex_buffer_object not found!\n");
exit(0);
}
UseBufferRange = glutExtensionSupported("GL_ARB_map_buffer_range");
printf("Use GL_ARB_map_buffer_range: %c\n", "NY"[UseBufferRange]);
printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
/* initially load buffer with zeros */
buf = (float *) calloc(1, BufferSize);
glGenBuffersARB(1, &BufferID);
glBindBufferARB(GL_ARRAY_BUFFER_ARB, BufferID);
glBufferDataARB(GL_ARRAY_BUFFER_ARB, BufferSize, buf, GL_DYNAMIC_DRAW_ARB);
free(buf);
}
int
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(800, 200);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
Win = glutCreateWindow(argv[0]);
glewInit();
glewInit();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Display);
glutIdleFunc(Anim ? Idle : NULL);
Init();
glutMainLoop();
return 0;
}
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