#include <assert.h> #include <stdio.h> #include <stdlib.h> #include <math.h> #include <string.h> #define GL_GLEXT_PROTOTYPES #include <GL/glut.h> static GLenum TexTarget = GL_TEXTURE_2D; static int TexWidth = 512, TexHeight = 512; static GLenum TexIntFormat = GL_RGBA; /* either GL_RGB or GL_RGBA */ static int Width = 512, Height = 512; static GLuint MyFB, TexObj; #define CheckError() assert(glGetError() == 0) GLenum doubleBuffer; static void Init(void) { fprintf(stderr, "GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER)); fprintf(stderr, "GL_VERSION = %s\n", (char *) glGetString(GL_VERSION)); fprintf(stderr, "GL_VENDOR = %s\n", (char *) glGetString(GL_VENDOR)); if (!glutExtensionSupported("GL_EXT_framebuffer_object")) { printf("GL_EXT_framebuffer_object not found!\n"); exit(0); } glGenFramebuffersEXT(1, &MyFB); glGenTextures(1, &TexObj); /* Make texture object/image */ glBindTexture(TexTarget, TexObj); glTexParameteri(TexTarget, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(TexTarget, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(TexTarget, GL_TEXTURE_BASE_LEVEL, 0); glTexParameteri(TexTarget, GL_TEXTURE_MAX_LEVEL, 0); glTexImage2D(TexTarget, 0, TexIntFormat, TexWidth, TexHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); { glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB); glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, TexTarget, TexObj, 0); glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); } } static void Reshape( int width, int height ) { glViewport( 0, 0, width, height ); glMatrixMode( GL_PROJECTION ); glLoadIdentity(); glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0); glMatrixMode( GL_MODELVIEW ); Width = width; Height = height; } static void Key(unsigned char key, int x, int y) { switch (key) { case 27: exit(1); default: return; } glutPostRedisplay(); } static void Draw( void ) { /* draw to texture image */ glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB); // glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT); // glReadBuffer(GL_COLOR_ATTACHMENT1_EXT); glViewport(0, 0, TexWidth, TexHeight); CheckError(); glClearColor(0.5, 0.5, 1.0, 0.0); glClear(GL_COLOR_BUFFER_BIT); CheckError(); if (0) { glBegin(GL_TRIANGLES); glColor3f(0,0,.7); glVertex3f( 0.9, -0.9, -30.0); glColor3f(.8,0,0); glVertex3f( 0.9, 0.9, -30.0); glColor3f(0,.9,0); glVertex3f(-0.9, 0.0, -30.0); glEnd(); } { GLubyte *buffer = malloc(Width * Height * 4); /* read from user framebuffer */ glReadPixels(0, 0, Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer); CheckError(); /* draw to window */ glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); glViewport(0, 0, Width, Height); /* Try to clear the window, but will overwrite: */ glClearColor(0.8, 0.8, 0, 0.0); glClear(GL_COLOR_BUFFER_BIT); glWindowPos2iARB(30, 30); glDrawPixels(Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer); free(buffer); } /* Bind normal framebuffer */ glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); glViewport(0, 0, Width, Height); if (0) { glBegin(GL_TRIANGLES); glColor3f(0,.7,0); glVertex3f( 0.5, -0.5, -30.0); glColor3f(0,0,.8); glVertex3f( 0.5, 0.5, -30.0); glColor3f(.9,0,0); glVertex3f(-0.5, 0.0, -30.0); glEnd(); } if (doubleBuffer) { glutSwapBuffers(); } CheckError(); } static GLenum Args(int argc, char **argv) { GLint i; doubleBuffer = GL_FALSE; for (i = 1; i < argc; i++) { if (strcmp(argv[i], "-sb") == 0) { doubleBuffer = GL_FALSE; } else if (strcmp(argv[i], "-db") == 0) { doubleBuffer = GL_TRUE; } else { fprintf(stderr, "%s (Bad option).\n", argv[i]); return GL_FALSE; } } return GL_TRUE; } int main( int argc, char *argv[] ) { GLenum type; glutInit(&argc, argv); if (Args(argc, argv) == GL_FALSE) { exit(1); } glutInitWindowPosition(100, 0); glutInitWindowSize( Width, Height ); type = GLUT_RGB; type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE; glutInitDisplayMode(type); if (glutCreateWindow(argv[0]) == GL_FALSE) { exit(1); } Init(); glutReshapeFunc(Reshape); glutKeyboardFunc(Key); glutDisplayFunc(Draw); glutMainLoop(); return 0; }