I am trying to render a simple 2d Image with the QOpenGLWidget using a quad as a texture. But no matter what I am trying, I always get a black box.
I have read many tutorials, I have a simple pixelbuffer like this
uchar* m_pData;
which stores my RGB values. This is valid, since I have it tested with glDrawPixles(). I will post the three most important functions considering the OpenGLWidget.
initializeGL() first:
void QGLImageviewer::initializeGL()
{
initializeOpenGLFunctions();
// Clear the color
float r = ((float)m_backColor.darker().red())/255.0f;
float g = ((float)m_backColor.darker().green())/255.0f;
float b = ((float)m_backColor.darker().blue())/255.0f;
glClearColor(r,g,b,1.0f);
// Set shading model.
glShadeModel(GL_SMOOTH);
// Set the viewport
glViewport(0.f, 0.f, m_origW, m_origH);
// Init. Projection Matrix
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, m_origW, m_origH,0.0,1.0,-1.0);
// Init Modelview Matrix
glClearColor(0.f, 0.f, 0.f, 1.f);
// Enable texturing
glEnable(GL_TEXTURE_2D);
// Generate texture ID
glGenTextures(1, &m_textureID);
// Bind texture ID
glBindTexture(GL_TEXTURE_2D, m_textureID);
// Set texture parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
//glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
//glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
// Generate Texture, and assign pixles to our texture ID
if (m_pData != nullptr)
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, m_origW, m_origH, 0, GL_RGB, GL_UNSIGNED_BYTE, (GLvoid*)m_pData);
}
else
{
qCritical("Buffer is empty!!");
}
// Unbind texture
glBindTexture(GL_TEXTURE_2D, NULL);
// Check for Error
GLenum error_ = glGetError();
if (error_ != GL_NO_ERROR)
{
qCritical("Error Loading Texture!");
}
}
Then paintGL():
void QGLImageviewer::paintGL()
{
makeCurrent();
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
// Clear Screen And Depth Buffer
glClear(GL_COLOR_BUFFER_BIT);
if (!(m_renderQtImg->isNull()))
{
//QImage image;
int imWidth = m_renderQtImg->width();
int imHeight = m_renderQtImg->height();
// The image has to be resized to fit the widget
if (imWidth != this->size().width() &&
imHeight != this->size().height())
{
imWidth = this->size().width();
imHeight = this->size().height();
}
else
{
//image = *m_renderQtImg;
imWidth = m_origW;
imHeight = m_origH;
}
if (m_textureID != 0)
{
glMatrixMode(GL_MODELVIEW);
// Remove any previous transformations
glLoadIdentity();
glPushMatrix();
// Move to rendering point
glTranslatef(0.f, 0.f, 0.f);
glColor3f(0.0f, 0.0f, 0.5f);
// Set texture ID
glBindTexture(GL_TEXTURE_2D, m_textureID);
glBegin(GL_QUADS);
glTexCoord2f(0.f, 0.f); glVertex2f(0.f, 0.f);
glTexCoord2f(1.f, 0.f); glVertex2f(imWidth, 0.f);
glTexCoord2f(1.f, 1.f); glVertex2f(imWidth, imHeight);
glTexCoord2f(0.f, 1.f); glVertex2f(0.f, imHeight);
glEnd();
//glDisable(GL_TEXTURE_2D);
glPopMatrix();
glFlush();
}
}
}
And last but not least resizeGL():
void QGLImageviewer::resizeGL(int width, int height)
{
makeCurrent();
glViewport(0,0,(GLint)width,(GLint)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
//gluOrtho2D(0.0, width, 0.0, height);
glOrtho(0.0, width, 0.0, height, 0.0, 1.0);
}
I am using Qt5.6 and the Microsoft Visual Studio 2015 compiler.
Damn, the problem was on
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, m_origW , m_origH, 0, GL_RGB, GL_UNSIGNED_BYTE, (float*)m_pData);
My member variables m_orgiW and m_orgiH were initialized to 0. So quite unsurprising that my code did not work.
For the record I will post my running code, the three most important functions of the QOpenGLWidget, hope that it will be useful to somebody with the same issue.
void QGLImageviewer::initializeGL()
{
initializeOpenGLFunctions();
float r = ((float)m_backColor.darker().red())/255.0f;
float g = ((float)m_backColor.darker().green())/255.0f;
float b = ((float)m_backColor.darker().blue())/255.0f;
glClearColor(r,g,b,1.0f);
// Generate texture ID
glGenTextures(1, &m_textureID);
// Bind texture ID
glBindTexture(GL_TEXTURE_2D, m_textureID);
if (m_pData != nullptr)
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, m_origW , m_origH, 0, GL_RGB, GL_UNSIGNED_BYTE, (float*)m_pData);
}
else
{
qCritical("Buffer is empty!!");
}
// Set texture parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); //IMPORTANT FOR NON POWER OF 2 TEXTURES
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
// Enable texturing Mapping
glEnable(GL_TEXTURE_2D);
// Enable Smooth Shading
glShadeModel(GL_SMOOTH);
// Black Background
glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
// Depth Buffer Setup
glClearDepth(1.0f);
// Enables Depth Testing
glEnable(GL_DEPTH_TEST);
// Type of depth testing to do
glDepthFunc(GL_LEQUAL);
// Really Nice Perspective Calculations
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
// Unbind Texture
glBindTexture(GL_TEXTURE_2D, NULL);
}
Now paintGL()
void QGLImageviewer::paintGL()
{
makeCurrent();
// Clear Screen And Depth Buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, m_textureID);
glBegin(GL_QUADS);
// Drawing the quad with the texture mapped on it
//
// OpenGL 2D Coordinates
// Sticking with the Coordinate Convention mentioned here
glTexCoord2f(1.0f, 0.0f); glVertex2f(m_width, 0.0f); // vertex 1
glTexCoord2f(1.0f, 1.0f); glVertex2f(m_width, m_height); // vertex 2
glTexCoord2f(0.0f, 1.0f); glVertex2f(0.0f, m_height); // vertex 3
glTexCoord2f(0.0f, 0.0f); glVertex2f(0.0f, 0.0f); // vertex 4
glEnd();
}
And resizeGL()
void QGLImageviewer::resizeGL(int width, int height)
{
makeCurrent();
m_width = width;
m_height = height;
// Compute aspect ratio of the new window
if (height == 0) height = 1; // To prevent divide by 0
GLfloat aspect = (GLfloat)width / (GLfloat)height;
// Set the viewport to cover the new window
glViewport(0, 0, width, height);
// Set the aspect ratio of the clipping area to match the viewport
glMatrixMode(GL_PROJECTION); // To operate on the Projection matrix
glLoadIdentity(); // Reset the projection matrix
glOrtho(0, m_width/ m_zoomFactor, m_height/ m_zoomFactor,0, -1, 1);
}
I am trying something quite easy, normally: applying a texture on the different surfaces of a cube.
I am able to apply it but it seems as if he just takes an average of the colors of my image.
why please?
my code:
void MyGLWidget::drawCube()
{
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
glLoadIdentity();
// glPushMatrix();
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glTranslatef( 0.5, 0, 0.0);
glRotatef(getCubeAngle(), 0.0f, 1.0f, 0.0f);
glTranslatef(0, 0, 0);
glDisable(GL_TEXTURE_GEN_S);
glDisable(GL_TEXTURE_GEN_T);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glBegin(GL_QUADS);
//back
glVertex3f(-0.1, 0.1,-0.1 );//upper left corner
glVertex3f(0.1, 0.1,-0.1); //uper right
glVertex3f(0.1,-0.1,-0.1 ); // down left
glVertex3f(-0.1,-0.1,-0.1); // down right
/* other code to create rest of the cube*/
glEnd();
glFlush();
// glPopMatrix();
}
void MyGLWidget::resizeGL(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glScalef(height *1./width, 1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
}
void MyGLWidget::myTextureMapping()
{
QImage t;
QImage b;
if(!b.load("..../myImage.bmp"))
{qDebug("error with image\n");}
t = QGLWidget::convertToGLFormat(b);
glGenTextures( 1, &texture[0] );
glBindTexture( GL_TEXTURE_2D, texture[0] );
glTexImage2D( GL_TEXTURE_2D, 0, 3, t.width(), t.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, t.bits() );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
}
void MyGLWidget::initializeGL()
{
myTextureMapping();
glEnable(GL_TEXTURE_2D);
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
glClearDepth(1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}
EDIT:
added those tex coordinates:
glTexCoord2f(-0.1, 0.1);
glVertex3f(-0.1, 0.1,0 );//upper left corner
glTexCoord2f(0.1, 0.1);
glVertex3f(0.1, 0.1,0); //uper right
glTexCoord2f(0.1, -0.1);
glVertex3f(0.1,-0.1,0 ); // down left
glTexCoord2f(-0.1, -0.1);
glVertex3f(-0.1,-0.1,0); // down right
But my image is bigger than the face of my cube:
source image : http://imgur.com/h48QARM
result in software: http://imgur.com/rxvK0Ot
You should be providing the texture co-ordinates for each vertex. What you have right now is just a position data for the Quad, texture co-ordinates are missing.
Have a look at this :
OpenGL Textured Cube Not Being Mapped Correctly
Try this :
glTexCoord2f(0, 0);
glVertex3f(-0.1, 0.1,0 );//upper left corner
glTexCoord2f(1, 0);
glVertex3f(0.1, 0.1,0); //uper right
glTexCoord2f(0, 1);
glVertex3f(-0.1,-0.1,0 ); // down left
glTexCoord2f(1, 1);
glVertex3f(0.1,-0.1,0); // down right
Isn't the texture coordinates wrong? To me it seems like you're going -0.1 to 0.1, while texture coordinates normally are defined in the interval [0,1].
Essentially, I'm rendering a raw buffer of pixels onto a texture, which is wrapped onto a quad.
My GL initiation code:
void INITOGL(int xres, int yres){
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
glClearDepth(1);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
//gluOrtho2D(0, xres, 0, yres);
}
Render loop code:
void RenderCycle(){
register MSG msg = {0};
while(1){
if(PeekMessage(&msg, 0, 0, 0, PM_REMOVE)){
TranslateMessage(&msg);
DispatchMessage(&msg);
}
glEnable(GL_TEXTURE_2D);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
//glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);//GL_LINEAR
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE/*GL_DECAL*/);
glTexImage2D( GL_TEXTURE_2D, 0, 3, 800, 600, 0, GL_RGB, GL_UNSIGNED_BYTE, framebuffer);//viewport virtual size
glClear(GL_COLOR_BUFFER_B
IT | GL_DEPTH_BUFFER_BIT);
glBegin(GL_POLYGON);
glTexCoord2f(0.0f, 1.0f);
glVertex3f(0, 0, 0.0f);
glTexCoord2f(1.0f, 1.0f);
glVertex3f( 800, 0, 0.0f);
glTexCoord2f(1.0f, 0.0f);
glVertex3f( 800, 600, 0.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f( 0, 600, 0.0f);
glEnd();
glDisable(GL_TEXTURE_2D);
SwapBuffers(hdc);
}
}
The resize function:
void ResizeViewport(int height, int width){
if(!height)height++;
//glMatrixMode(GL_MODELVIEW);
//glLoadIdentity();
//gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_PROJECTION);
glViewport(0,0,width,height);
//gluOrtho2D(0, width, 0, height);
glLoadIdentity();
}
The buffer that holds the RGB data is just set to red using a for loop, and this is the output.
Have I improperly set my viewport, not scaled something correctly, or am I just completely missing something? If you need any more information, just ask. I have given all of the opengl sided code, the rest shouldn't make a difference. In theory, it should render red to the entire screen.
I created 4 textures and attach them to FBO, named fbo_texture0 - fbo_texture3. All of them are successfully created, as given by the following screenshot:
image 1
Now, i wanted to create the 5th texture which is obtained from the previous textures (fbo_texture0 - fbo_texture3) using GLSL. For now, i just want to copy the first texture into the fifth texture. Unfortunately, here is what i got:
image 2
The question is:
How can i access these fbo textures in GLSL?
How can i create the 5th texture? (or copy from the first texture to the fifth texture?)
Here's the complete code of the program (in case needed):
#include <windows.h>
#include <GL/glew.h> // Include the GLEW header file
#include <GL/glut.h> // Include the GLUT header file
#include <iostream> // Allow us to print to the console
using namespace std;
bool* keyStates = new bool[256]; // Create an array of boolean values of length 256 (0-255)
unsigned int fbo; // The frame buffer object
unsigned int fbo_depth; // The depth buffer for the frame buffer object
unsigned int fbo_texture0; // The texture object to write our frame buffer object to
unsigned int fbo_texture1;
unsigned int fbo_texture2;
unsigned int fbo_texture3;
unsigned int fbo_texture4;
GLhandleARB shaderProgram;
GLhandleARB vertexShader;
GLhandleARB fragmentShader;
int window_width = 500; // The width of our window
int window_height = 500; // The height of our window
void initFrameBufferDepthBuffer(void) {
glGenRenderbuffers(1, &fbo_depth); // Generate one render buffer and store the ID in fbo_depth
glBindRenderbuffer(GL_RENDERBUFFER, fbo_depth); // Bind the fbo_depth render buffer
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, window_width, window_height); // Set the render buffer storage to be a depth component, with a width and height of the window
glBindRenderbuffer(GL_RENDERBUFFER, 0); // Unbind the render buffer
}
void initFrameBufferTextures(void) {
glGenTextures(1, &fbo_texture0); // Generate one ture
glBindTexture(GL_TEXTURE_2D, fbo_texture0); // Bind the ture fbo_texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
glGenTextures(1, &fbo_texture1); // Generate one ture
glBindTexture(GL_TEXTURE_2D, fbo_texture1); // Bind the ture fbo_texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
glGenTextures(1, &fbo_texture2); // Generate one ture
glBindTexture(GL_TEXTURE_2D, fbo_texture2); // Bind the ture fbo_texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
glGenTextures(1, &fbo_texture3); // Generate one ture
glBindTexture(GL_TEXTURE_2D, fbo_texture3); // Bind the ture fbo_texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
glGenTextures(1, &fbo_texture4); // Generate one ture
glBindTexture(GL_TEXTURE_2D, fbo_texture4); // Bind the ture fbo_texture
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, window_width, window_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); // Create a standard ture with the width and height of our window
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
}
void printInfoLog(GLhandleARB obj)
{
int infologLength = 0;
int charsWritten = 0;
char* infoLog;
glGetObjectParameterivARB(obj, GL_OBJECT_INFO_LOG_LENGTH_ARB, &infologLength);
if (infologLength > 0)
{
infoLog = (char*)malloc(infologLength);
glGetInfoLogARB(obj, infologLength, &charsWritten, infoLog);
printf("%s\n",infoLog);
free(infoLog);
}
}
void initFrameBuffer(void) {
initFrameBufferDepthBuffer(); // Initialize our frame buffer depth buffer
initFrameBufferTextures(); // Initialize our frame buffer ture
glGenFramebuffers(1, &fbo); // Generate one frame buffer and store the ID in fbo
glBindFramebuffer(GL_FRAMEBUFFER, fbo); // Bind our frame buffer
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fbo_texture0, 0);// Attach the ture fbo_texturen to the color buffer in our frame buffer
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, fbo_texture1, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_2D, fbo_texture2, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT3, GL_TEXTURE_2D, fbo_texture3, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT4, GL_TEXTURE_2D, fbo_texture4, 0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, fbo_depth); // Attach the depth buffer fbo_depth to our frame buffer
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER); // Check that status of our generated frame buffer
if (status != GL_FRAMEBUFFER_COMPLETE) // If the frame buffer does not report back as complete
{
cout << "Couldn't create frame buffer" << endl; // Output an error to the console
exit(0); // Exit the application
}
glBindFramebuffer(GL_FRAMEBUFFER, 0); // Unbind our frame buffer
}
void init(void) {
//glEnable(GL_TEXTURE_2D); // Enable turing so we can bind our frame buffer ture
glEnable(GL_DEPTH_TEST); // Enable depth testing
initFrameBuffer(); // Create our frame buffer object
}
void keyOperations (void) {
if (keyStates['a']) { // If the a key has been pressed
// Perform 'a' key operations
}
}
void renderTextures(void) {
glBindFramebuffer(GL_FRAMEBUFFER, fbo); // Bind our frame buffer for rendering
glPushAttrib(GL_VIEWPORT_BIT | GL_ENABLE_BIT); // Push our glEnable and glViewport states
glViewport(0, 0, window_width, window_height); // Set the size of the frame buffer view port
glDrawBuffer(GL_COLOR_ATTACHMENT0);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set the clear colour
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
glLoadIdentity();// Reset the modelview matrix
glTranslatef(0.0f, 0.0f, -5.0f);
//Add ambient light
GLfloat ambientColor[] = {0.2f, 0.2f, 0.2f, 1.0f}; //Color(0.2, 0.2, 0.2)
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor);
//Add positioned light
GLfloat lightColor0[] = {0.5f, 0.5f, 0.5f, 1.0f}; //Color (0.5, 0.5, 0.5)
GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 1.0f}; //Positioned at (4, 0, 8)
glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0);
glLightfv(GL_LIGHT0, GL_POSITION, lightPos0);
//Add directed light
GLfloat lightColor1[] = {0.5f, 0.2f, 0.2f, 1.0f}; //Color (0.5, 0.2, 0.2)
//Coming from the direction (-1, 0.5, 0.5)
GLfloat lightPos1[] = {-1.0f, 0.5f, 0.5f, 0.0f};
glLightfv(GL_LIGHT1, GL_DIFFUSE, lightColor1);
glLightfv(GL_LIGHT1, GL_POSITION, lightPos1);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_LIGHT1);
glEnable(GL_DEPTH_TEST);
glutSolidTeapot(2.0);
glColor3f(0.1,0.2,0.7);
glDrawBuffer(GL_COLOR_ATTACHMENT1);
glClearColor(0.5f, 0.5f, 0.0f, 1.0f); // Set the clear colour
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
glLoadIdentity();// Reset the modelview matrix
glTranslatef(0.0f, 0.0f, -5.0f);
glutSolidTorus(0.80, 1.6, 50, 100);
glColorMaterial ( GL_FRONT_AND_BACK, GL_EMISSION ) ;
glEnable ( GL_COLOR_MATERIAL ) ;
glDrawBuffer(GL_COLOR_ATTACHMENT2);
glClearColor(0.5f, 0.0f, 0.0f, 1.0f); // Set the clear colour
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
glLoadIdentity();// Reset the modelview matrix
glTranslatef(0.0f, 0.0f, -2.0f);
glutSolidTetrahedron();
glColorMaterial ( GL_FRONT_AND_BACK, GL_EMISSION ) ;
glEnable ( GL_COLOR_MATERIAL ) ;
glDrawBuffer(GL_COLOR_ATTACHMENT3);
glClearColor(0.5f, 0.0f, 0.3f, 1.0f); // Set the clear colour
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear the depth and colour buffers
glLoadIdentity();// Reset the modelview matrix
glTranslatef(0.0f, 0.0f, -2.0f);
glutSolidOctahedron();
glColorMaterial ( GL_FRONT_AND_BACK, GL_EMISSION ) ;
glEnable ( GL_COLOR_MATERIAL ) ;
glBindFramebuffer(GL_FRAMEBUFFER, 0); // Unbind our ture
glActiveTexture(GL_TEXTURE0);
//glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, fbo_texture0);
glUniform1i(glGetUniformLocation(shaderProgram, "tex0"), 0);
glActiveTexture(GL_TEXTURE1);
//glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, fbo_texture1);
glUniform1i(glGetUniformLocation(shaderProgram, "tex1"), 1);
glActiveTexture(GL_TEXTURE2);
//glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, fbo_texture2);
glUniform1i(glGetUniformLocation(shaderProgram, "tex2"), 2);
glActiveTexture(GL_TEXTURE3);
//glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, fbo_texture3);
glUniform1i(glGetUniformLocation(shaderProgram, "tex3"), 3);
glPopAttrib(); // Restore our glEnable and glViewport states
glutSwapBuffers();
}
static char* textFileRead(const char *fileName) {
char* text;
if (fileName != NULL) {
FILE *file = fopen(fileName, "rt");
if (file != NULL) {
fseek(file, 0, SEEK_END);
int count = ftell(file);
rewind(file);
if (count > 0) {
text = (char*)malloc(sizeof(char) * (count + 1));
count = fread(text, sizeof(char), count, file);
text[count] = '\0';
}
fclose(file);
}
}
return text;
}
void initShader(){
char* vsSource = textFileRead("./shader/multitexture.vs");
char* fsSource = textFileRead("./shader/multitexture.fs");
printf("%s\n",fsSource);
vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, (const GLchar **)(&vsSource), NULL);
glCompileShader(vertexShader);
printInfoLog(vertexShader);
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, (const GLchar **)(&fsSource), NULL);
glCompileShader(fragmentShader);
printInfoLog(fragmentShader);
delete [] vsSource;
delete [] fsSource;
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
}
void display (void) {
keyOperations(); // Perform any key presses
glUseProgram(0);
renderTextures(); // Render our teapot scene into our frame buffer
GLsync s = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
glUseProgram(shaderProgram);
glClearColor(0.0f, 1.0f, 0.0f, 1.0f); // Clear the background of our window to red
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Clear the colour buffer (more buffers later on)
glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations
glTranslatef(-4.7f, 1.0f, -4.0f);
glWaitSync(s, 0, GL_TIMEOUT_IGNORED);
glDeleteSync(s);
glBindTexture(GL_TEXTURE_2D, fbo_texture0); // Bind our frame buffer ture
glBegin(GL_QUADS);
glColor4f(1, 1, 1, 1);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
glTexCoord2f(1.0f, 1.0f);
glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
glTexCoord2f(1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
glEnd();
glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures
glLoadIdentity();
glTranslatef(-2.5f, 1.0f, -4.0f);
glBindTexture(GL_TEXTURE_2D, fbo_texture1); // Bind our frame buffer ture
glBegin(GL_QUADS);
glColor4f(1, 1, 1, 1);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
glTexCoord2f(1.0f, 1.0f);
glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
glTexCoord2f(1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
glEnd();
glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures
glLoadIdentity();
glTranslatef(-0.3f, 1.0f, -4.0f);
glBindTexture(GL_TEXTURE_2D, fbo_texture2); // Bind our frame buffer ture
glBegin(GL_QUADS);
glColor4f(1, 1, 1, 1);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
glTexCoord2f(1.0f, 1.0f);
glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
glTexCoord2f(1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
glEnd();
glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures
glLoadIdentity();
glTranslatef(1.9f, 1.0f, -4.0f);
glBindTexture(GL_TEXTURE_2D, fbo_texture3); // Bind our frame buffer ture
glBegin(GL_QUADS);
glColor4f(1, 1, 1, 1);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
glTexCoord2f(1.0f, 1.0f);
glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
glTexCoord2f(1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
glEnd();
glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures
glLoadIdentity();
glTranslatef(4.1f, 1.0f, -4.0f);
glBindTexture(GL_TEXTURE_2D, fbo_texture4); // Bind our frame buffer ture
glBegin(GL_QUADS);
glColor4f(1, 1, 1, 1);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
glTexCoord2f(1.0f, 1.0f);
glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
glTexCoord2f(1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
glEnd();
glBindTexture(GL_TEXTURE_2D, 0); // Unbind any tures
glutSwapBuffers();
}
void reshape (int width, int height) {
glViewport(0, 0, (GLsizei)width, (GLsizei)height); // Set our viewport to the size of our window
glMatrixMode(GL_PROJECTION); // Switch to the projection matrix so that we can manipulate how our scene is viewed
glLoadIdentity(); // Reset the projection matrix to the identity matrix so that we don't get any artifacts (cleaning up)
gluPerspective(60, (GLfloat)width / (GLfloat)height, 1.0, 100.0); // Set the Field of view angle (in degrees), the aspect ratio of our window, and the new and far planes
glMatrixMode(GL_MODELVIEW); // Switch back to the model view matrix, so that we can start drawing shapes correctly
}
void keyPressed (unsigned char key, int x, int y) {
keyStates[key] = true; // Set the state of the current key to pressed
}
void keyUp (unsigned char key, int x, int y) {
keyStates[key] = false; // Set the state of the current key to not pressed
}
int main (int argc, char **argv) {
glutInit(&argc, argv); // Initialize GLUT
glutInitDisplayMode (GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA); // Set up a basic display buffer (only single buffered for now)
glutInitWindowSize (1280, 500); // Set the width and height of the window
glutInitWindowPosition (100, 100); // Set the position of the window
glutCreateWindow ("OpenGL FBO"); // Set the title for the window
if (GLEW_OK != glewInit()) {
std::cout << "Couldn't initialize GLEW" << std::endl;
exit(0);
}
initShader();
init();
glutDisplayFunc(display); // Tell GLUT to use the method "display" for rendering
glutIdleFunc(display); // Tell GLUT to use the method "display" for rendering
glutReshapeFunc(reshape); // Tell GLUT to use the method "reshape" for reshaping
glutKeyboardFunc(keyPressed); // Tell GLUT to use the method "keyPressed" for key presses
glutKeyboardUpFunc(keyUp); // Tell GLUT to use the method "keyUp" for key up events
glutMainLoop(); // Enter GLUT's main loop
}
Here is the vertex shader:
void main(void)
{
gl_TexCoord[0] = gl_MultiTexCoord0;
gl_Position = ftransform();
}
And here is the fragment shader:
uniform sampler2D tex0;
uniform sampler2D tex1;
uniform sampler2D tex2;
uniform sampler2D tex3;
void main(void)
{
gl_FragColor = texture2D(tex0, gl_TexCoord[0].st);
}
EDIT #1
After modifying the code as suggested by #Damon (the code has been edited as well) , here's the screenshot of the result:
image 3
Now, I don't really know what the problem actually is. I tried to change the fragment shader to access another texture e.g. gl_FragColor = texture2D(tex2, gl_TexCoord[0].st); but i still got the same display as above. So i think it is definitely not the modelview/projection problem.
EDIT #2
The problem still left unclear. However, I tried to give only one glActiveTexture(GL_TEXTUREn); command at the program, and comment out other glActiveTexture command (without shader modification), and got the following result:
image 4 Only glActiveTexture(GL_TEXTURE0);activated.
image 5 Only glActiveTexture(GL_TEXTURE1);activated.
image 6 Only glActiveTexture(GL_TEXTURE2);activated.
image 7 Only glActiveTexture(GL_TEXTURE3);activated.
When at least 2 glActiveTexture(GL_TEXTUREn); activated, i got the same result as image 5. That left me wondering what the problem actually is.
initShader compiles and links a shader. You seem to be binding the textures to texture units within renderTextures in an OK manner, too (after unbinding the FBO, which is important to sync). So far so good, but I can't find glUseProgram anywhere in the code. That would mean the rendering falls back to fixed function, which does not have any textures bound at that time.
The fragment shader reads only from tex0, so of course you wouldn't expect to see tex1-tex3 anyway (but I guess that's just the minimum working example code).
Other than that, it looks OK from what I can see by reading over the code in 5 mins.
(As a sidenote: init calls glEnable(GL_TEXTURE_2D), this is not strictly wrong, but useless as soon as you use a shader, see this.)
How about this:
glBindFramebuffer(GL_FRAMEBUFFER, fbo); // Bind our frame buffer for rendering
glDrawBuffer(GL_COLOR_ATTACHMENT4);
glBindTexture(GL_TEXTURE_2D, fbo_texture0); // bind texture that is rendered in 0-th attachment
glBegin(GL_QUADS);
glColor4f(1, 1, 1, 1);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, 0.0f); // The bottom left corner
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 0.0f); // The top left corner
glTexCoord2f(1.0f, 1.0f);
glVertex3f(1.0f, 1.0f, 0.0f); // The top right corner
glTexCoord2f(1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f); // The bottom right corner
glEnd();
glBindFramebuffer(GL_FRAMEBUFFER, 0);
You just render into 4th attachment with binded texture from 0-th attachment.