OpenGL offscreen rendered texture not displaying on screen - opengl

Question

I am having difficulty getting a offscreen rendered texture to to be displayed. I have checked round the web and other questions and am clearly missing something.
I am new to OpenGL so may well be making some naive errors. It is part of a routine to add post processing using a shader to modify the firestor/secondlife viewer project to an equifisheye projection. My test code is based around the GLEW and GLUT framework using OpenGL 1.3 as the viewer is designed to run on older platforms.
The approach is:
set up and initialise the FBO, Render buffers and textures to draw to.
initilise various default settings for drawing the glutCube and glutTeapot :)
The display function
a) using the default framebuffer draws a rotating cube (works fine)
b) the texture is then drawn to
OUTPUT: all black and not the rotating cube.
My code is:
GLuint buffer_fbo;
GLuint bufferColtexture;
GLuint depthBuffer_rb;
typedef struct {
int width;
int height;
char* title;
float field_of_view_angle;
float z_near;
float z_far;
} glutWindow;
glutWindow win;
//
void ShutDown(void)
{
glDeleteFramebuffersEXT(1, &buffer_fbo);
glDeleteRenderbuffersEXT(1, &depthBuffer_rb);
glDeleteTextures(1,&bufferColtexture);
}
float g_potrotation = 0;
float g_potrotation_speed = 0.2f;
float xrot =0;
float yrot = 0;
float zrot = 0;
GLenum g_Drawbuffers[2] = {GL_COLOR_ATTACHMENT0_EXT };
void setupFBO(void)
{
// *********** set up scene FBO including dept buffers and their textures ****************
glGenFramebuffersEXT(1, &buffer_fbo);
// set up render buffers for depth info
glGenRenderbuffersEXT(1, &depthBuffer_rb);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthBuffer_rb);
glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, win.width, win.height);
// Genrate texture to render to
glGenTextures(1, &bufferColtexture);
glBindTexture(GL_TEXTURE_2D, bufferColtexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, win.width, win.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
// attach texture to render to to fbo
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, buffer_fbo);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, bufferColtexture, 0);
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depthBuffer_rb);
GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT); // check frame buffer
if(status != GL_FRAMEBUFFER_COMPLETE_EXT)
{
printf("FRAMEBUFFER status error %i \n",status);
exit(1);
}
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); // bind back to default
}
void initialise()
{
setupFBO();
// select projection matrix
glMatrixMode(GL_PROJECTION);
// set the viewport
glViewport(0, 0, win.width, win.height);
// set matrix mode
glMatrixMode(GL_PROJECTION);
// reset projection matrix
glLoadIdentity();
GLfloat aspect = (GLfloat) win.width / win.height;
// set up a perspective projection matrix
gluPerspective(win.field_of_view_angle, aspect, win.z_near, win.z_far);
// specify which matrix is the current matrix
glMatrixMode(GL_MODELVIEW);
glShadeModel( GL_SMOOTH );
// specify the clear value for the depth buffer
glClearDepth( 1.0f );
glEnable( GL_DEPTH_TEST );
glDepthFunc( GL_LEQUAL );
// specify implementation-specific hints
glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );
GLfloat amb_light[] = { 0.1, 0.1, 0.1, 1.0 };
GLfloat diffuse[] = { 0.6, 0.6, 0.6, 1 };
GLfloat specular[] = { 0.7, 0.7, 0.3, 1 };
glLightModelfv( GL_LIGHT_MODEL_AMBIENT, amb_light );
glLightfv( GL_LIGHT0, GL_DIFFUSE, diffuse );
glLightfv( GL_LIGHT0, GL_SPECULAR, specular );
glEnable( GL_LIGHT0 );
glEnable( GL_COLOR_MATERIAL );
glShadeModel( GL_SMOOTH );
glLightModeli( GL_LIGHT_MODEL_TWO_SIDE, GL_FALSE );
glDepthFunc( GL_LEQUAL );
glEnable( GL_DEPTH_TEST );
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glClearColor(0.5, 0.5, 0.5, 1.0);
}
void drawquad(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
glDisable(GL_LIGHTING); // This was the cause of the problem, disable lighting worked!
glLoadIdentity(); // Reset The View
glTranslatef(0.0f,0.0f,-5.0f);
glTranslatef(0.0f,0.0f,-5.0f);
glRotatef(xrot,1.0f,0.0f,0.0f);
glRotatef(yrot,0.0f,1.0f,0.0f);
glRotatef(zrot,0.0f,0.0f,1.0f);
glBindTexture(GL_TEXTURE_2D, bufferColtexture);
glBegin(GL_QUADS);
// Front Face
glTexCoord2f(0.0f, 0.0f); glVertex2f(-1.0f, -1.0f);
glTexCoord2f(1.0f, 0.0f); glVertex2f( 1.0f, -1.0f);
glTexCoord2f(1.0f, 1.0f); glVertex2f( 1.0f, 1.0f);
glTexCoord2f(0.0f, 1.0f); glVertex2f(-1.0f, 1.0f);
glEnd();
xrot+=0.3f;
yrot+=0.2f;
zrot+=0.4f;
glEnable(GL_LIGHTING); // now reenabling the lighting. after adding to fix code.
}
void display(void)
{
// set red background
// draw to fbo
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT,0);
// Clear Screen and Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_TEXTURE_2D);
// set drawing a rotating cube as per default
glLoadIdentity();
// Define a viewing transformation
gluLookAt( 3,1,0, 0,0,0, 0,1,0);
// Push and pop the current matrix stack.
// This causes that translations and rotations on this matrix wont influence others.
glPushMatrix();
glColor3f(0,1,0);
glTranslatef(0,0,0);
glRotatef(g_potrotation,0,1,0);
glRotatef(90,0,1,0);
// Draw the solid cube
glutSolidCube(1);
glPopMatrix();
// draw teapot to fbo
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, buffer_fbo);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT,depthBuffer_rb);
// Clear Screen and Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
// Define a viewing transformation
gluLookAt( 4,2,0, 0,0,0, 0,1,0);
// Push and pop the current matrix stack.
// This causes that translations and rotations on this matrix wont influence others.
glPushMatrix();
glColor3f(1,0,0);
glTranslatef(0,0,0);
glRotatef(g_potrotation,0,1,0);
glRotatef(90,0,1,0);
// Draw the teapot
glutSolidTeapot(1);
glPopMatrix();
g_potrotation += g_potrotation_speed;
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT,0); // reset to default Frame and Render buffer
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT,0);
drawquad();
glutSwapBuffers();
}
// informs OpenGL that window size has changed.
void reshape(int width, int height)
{
}
void idle(void)
{
glutPostRedisplay();
}
int checkglewOK()
{
if (GLEW_ARB_vertex_shader && GLEW_ARB_fragment_shader)
printf("Ready for GLSL\n");
else {
printf("Not totally ready :( \n");
exit(1);
};
}
void keyboard (unsigned char key, int mousePositionX, int mousePositionY)
{
switch (key)
{
case KEY_ESCAPE:
exit (0);
break;
default:
break;
}
}
int main(int argc, char** argv)
{
// set window values
win.width = 640;
win.height = 480;
win.title = "Shader Test";
win.field_of_view_angle = 45;
win.z_near = 1.0f;
win.z_far = 500.0f;
////////////////////////////////////////////////////////
// Initialise and Create Window
////////////////////////////////////////////////////////
glutInit(&argc, argv);
// set modes RGB-Alpha, doble bufferedd (prevent flickering)
// has a depth buffer to ensure that 3D object overlp OK
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH); // set display mode
// define window size
glutInitWindowSize(win.width, win.height);
glutCreateWindow(win.title); // create the window
glewInit(); // Glew Init occurs after Create Window !!!
checkglewOK();
glutDisplayFunc(display); // register display function
//glutReshapeFunc(reshape); // register resize function
glutIdleFunc(idle); // register idel function
glutKeyboardFunc(keyboard);
initialise();
glutMainLoop(); // run glut main loop
ShutDown();
return EXIT_SUCCESS;
}