/* * 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); glEnableClientState(GL_VERTEX_ARRAY); glColorPointer(3, GL_FLOAT, 24, (void*) 12); glEnableClientState(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; }