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I'm trying to make the gluLookAt() function so that when I press the up & down key the camera moves around the X axis
I'm trying a method I saw at: http://www.lighthouse3d.com/tutorials/glut-tutorial/keyboard-example-moving-around-the-world/
but it's not working for me. Anyone knows an easier way? and where should I put the gluLookAt() so on myDisplay() func?
#include"glut.h"
#include<cmath>
#include<iostream>
using namespace std;
float xr = 0, yr = 0; //to control the object's movement from left to right
// actual vector representing the camera's direction
float lx = 0.0f, lz = -1.0f;
// XZ position of the camera
float x = 0.0f, z = 5.0f;
GLfloat angle = 0.0f;
int refreshmill = 1;
void timer(int value) { //to control the rotation of the object
glutPostRedisplay();
glutTimerFunc(refreshmill, timer, 0);
}
void myDisplay(void) {
//Circle One
float theta;
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1, 0, 0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
glBegin(GL_POLYGON);
for (int x = 0; x < 360; x++) {
theta = x * 3.142 / 180;
glVertex2f(150 * cos(theta)+xr,150 * sin(theta)+yr);
}
glEnd();
glPopMatrix();
//Circle Two
float theta2;
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
glTranslatef(0.5f, 0.0f, 0.0f); // rotation
glRotatef(angle, 0.0f, 0.0f, -0.5f); // rotation
glBegin(GL_POLYGON);
glColor3f(0, 0, 1);
for (int x = 0; x < 360; x++) {
theta2 = x * 3.142 / 180;
glVertex2f(150 + 15 * cos(theta2) + xr, 15 * sin(theta2) + yr);
}
glutSwapBuffers();
angle += 0.2; // rotation
glEnd();
glPopMatrix();
//Draw Star
glColor3ub(119, 193, 15);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
glBegin(GL_POLYGON);
glVertex2d(15+xr, 60+yr);
glVertex2d(75+xr, 75+yr); //right peak
glVertex2d(15+xr, 90+yr);
glVertex2d(0+xr, 150+yr); //Up-peak Changed
glVertex2d(-15+xr, 90+yr);
glVertex2d(-75+xr,75+yr);
glVertex2d(-15+xr, 60+yr);
glVertex2d(0+xr,0+yr);
glEnd();
glPopMatrix();
glFlush();
glutPostRedisplay();
glutSwapBuffers();
}
void renderScene(void) {
// Clear Color and Depth Buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Reset transformations
glLoadIdentity();
// Set the camera
gluLookAt(x, 1.0f, z,
x + lx, 1.0f, z + lz,
0.0f, 1.0f, 0.0f);
// Draw ground
glColor3f(0.9f, 0.9f, 0.9f);
glBegin(GL_QUADS);
glVertex3f(-100.0f, 0.0f, -100.0f);
glVertex3f(-100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, -100.0f);
glEnd();
myDisplay();
glutSwapBuffers();
}
//Move to left or right
void keyboard(int key, int x, int y) {
float fraction = 0.1f;
switch (key) {
case GLUT_KEY_RIGHT:
xr++;
cout << x << endl;
glutPostRedisplay();
break;
case GLUT_KEY_LEFT:
xr--;
cout << x << endl;
glutPostRedisplay();
break;
case GLUT_KEY_UP:
angle -= 0.01f;
lx = sin(angle);
lz = -cos(angle);
break;
case GLUT_KEY_DOWN:
angle += 0.01f;
lx = sin(angle);
lz = -cos(angle);
break;
}
}
void init() {
glClearColor(0, 0, 0, 1);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-250, 250, -250, 250); //IMPORTANT- Define from negative to positive
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char** argv) {
// init GLUT and create window
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(500, 500);
glutInitWindowPosition(0, 0);
glutCreateWindow("Homework: Circle");
// register callbacks
glutDisplayFunc(myDisplay);
glutDisplayFunc(renderScene);
glutIdleFunc(renderScene);
glutTimerFunc(0,timer,0);
glutSpecialFunc(keyboard);
// OpenGL init
init();
// enter GLUT event processing cycle
glutMainLoop();
}
First of all there should be only 1 display call back function:
int main(int argc, char** argv) {
// [...]
// glutDisplayFunc(myDisplay); <----- DELETE!!!
glutDisplayFunc(renderScene);
// glutIdleFunc(renderScene); <----- DELETE!!!
// [...]
}
Setup an an orthographic projection with an extended near and far plane. If the object is rotated around the X axis, it takes space in the 3 dimensions:
void init() {
glClearColor(0, 0, 0, 1);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-250, 250, -250, 250, -250, 250); // <----
glMatrixMode(GL_MODELVIEW);
}
Add a variable anglaX which is changed in the keyboard event:
float angleX = 0.0f;
void keyboard(int key, int x, int y) {
switch (key) {
case GLUT_KEY_RIGHT: xr++; break;
case GLUT_KEY_LEFT: xr--; break;
case GLUT_KEY_UP: angleX -= 1.0f; break;
case GLUT_KEY_DOWN: angleX += 1.0f; break;
}
}
Rotate the model, after the view was set:
gluLookAt(x, 0.0f, z, x, 0.0f, z-1.0f, 0.0f, 1.0f, 0.0f);
glRotatef(angleX, 1, 0, 0);
Don't do any calls to glutSwapBuffers(), glFlush() and glutPostRedisplay(), except at the end of renderScene:
void timer(int value) { //to control the rotation of the object
// glutPostRedisplay(); <--- DELETE
glutTimerFunc(refreshmill, timer, 0);
}
void myDisplay(void) {
//Circle One
float theta;
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1, 0, 0);
glPushMatrix();
glBegin(GL_POLYGON);
for (int x = 0; x < 360; x++) {
theta = x * 3.142 / 180;
glVertex2f(150 * cos(theta)+xr,150 * sin(theta)+yr);
}
glEnd();
glPopMatrix();
//Circle Two
float theta2;
glPushMatrix();
glTranslatef(0.5f, 0.0f, 0.0f); // rotation
glRotatef(angle, 0.0f, 0.0f, -0.5f); // rotation
glBegin(GL_POLYGON);
glColor3f(0, 0, 1);
for (int x = 0; x < 360; x++) {
theta2 = x * 3.142 / 180;
glVertex2f(150 + 15 * cos(theta2) + xr, 15 * sin(theta2) + yr);
}
angle += 0.2; // rotation
glEnd();
glPopMatrix();
//Draw Star
glColor3ub(119, 193, 15);
glPushMatrix();
glBegin(GL_POLYGON);
glVertex2d(15+xr, 60+yr);
glVertex2d(75+xr, 75+yr); //right peak
glVertex2d(15+xr, 90+yr);
glVertex2d(0+xr, 150+yr); //Up-peak Changed
glVertex2d(-15+xr, 90+yr);
glVertex2d(-75+xr,75+yr);
glVertex2d(-15+xr, 60+yr);
glVertex2d(0+xr,0+yr);
glEnd();
glPopMatrix();
}
void renderScene(void) {
// Clear Color and Depth Buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Reset transformations
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// Set the camera
gluLookAt(x, 0.0f, z, x, 0.0f, z-1.0f, 0.0f, 1.0f, 0.0f);
glRotatef(angleX, 1, 0, 0);
// Draw ground
glColor3f(0.9f, 0.9f, 0.9f);
glBegin(GL_QUADS);
glVertex3f(-100.0f, 0.0f, -100.0f);
glVertex3f(-100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, -100.0f);
glEnd();
myDisplay();
glFlush();
glutPostRedisplay();
glutSwapBuffers();
}
Further I recommend to use double buffering:
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
You can init your camera with gluLookAt at init(), then rotate it when arrow keys pressed. If you want to rotate camera around it's local x axis, assume your initial modelview matrix is V, newly happened rotation around x axis is R, you need to set modelview matrix to R*V, not V*R.
case GLUT_KEY_UP:
GLfloat temp[16];
glGetFloatv(GL_MODELVIEW_MATRIX, temp);
glLoadIdentity();
glRotate(stepAngle, 1, 0, 0); // calculate stepAngle by your self
glMultMatrixf(temp);
break;
You don need to reset modelview matrix during rendering, view part is already done, make sure you restore it after rendering the whole scene:
glPushMatrix(GL_MODELVIEW_MATRIX)
// don't call glLoadIdentity() here, you don't need to reset view part.
...
...
glPopMatrix()
I'm trying to implement camera functionality on a simple scene but the output is distored. I think it has something to do with perspective projection or maybe I'm using the gluLookAt() function wrong but I can't seem to pinpoint the problem. Whenever I press the arrow keys to more the camera the view keeps getting distorted. The camera code works fine in another example. I've used the exact same code with the display replaced for my scene. I have tried different arguments for gluLookAt() and even tried ortho projection but nothing seems to work.
Before camera implementation:
After camera implementation:
Code:
#include <Windows.h>
#include <math.h>
#include "glut.h"
float angle = 0.0f;
float lx = 0.0f, lz = -0.1f;
float x = 0.0f, z = 0.5f;
float deltaAngle = 0.0f;
float deltaMove = 0;
double rot = 0;
double doorAngle = 0;
double carMove = -0.75; //Initially car positioned at the start of road
void myInit(void)
{
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowSize(1000, 480);
glutInitWindowPosition(100, 150);
glutCreateWindow(" project part1 ");
glClearColor(0.333, 0.725, 0.905, 0);
glColor3f(0.0f, 0.0f, 0.0f);
}
void reshape(int w, int h) {
if (h == 0)
h = 1;
float ratio = w* 1.0 / h;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0, 0, w, h);
gluPerspective(45.0f, ratio, 0.1f, 20.0f);
glMatrixMode(GL_MODELVIEW);
}
void computePos(float deltaMove) //compute camera position
{
x += deltaMove * lx * 0.1f;
z += deltaMove * lz * 0.1f;
}
void computeDir(float deltaAngle)//compute camra direction
{
angle += deltaAngle;
lx = sin(angle);
lz = -cos(angle);
}
void display(void)
{
if (deltaMove)
computePos(deltaMove);
if (deltaAngle)
computeDir(deltaAngle);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
gluLookAt(x, 0.0f, z, x + lx, 0.0f, z + lz, 0.0f, 1.0f, 0.0f);
//display quads road
glPushMatrix();
glLineWidth(3.0);
glColor3f(0.474, 0.552, 0.603);
glBegin(GL_QUADS);//grey road
glTexCoord2f(0.0, 0.0);
glVertex3f(-1, 0, 0);
glTexCoord2f(0.0, 1.0);
glVertex3f(1, 0, 0);
glTexCoord2f(1.0, 1.0);
glVertex3f(1, -1, 0);
glTexCoord2f(1.0, 0.0);
glVertex3f(-1, -1, 0);
glEnd();
//green grass above
glColor3f(0.305, 0.513, 0.341);
glBegin(GL_QUADS);
glVertex3f(-1, 0, 0);
glVertex3f(1, 0, 0);
glVertex3f(1, -0.1, 0);
glVertex3f(-1, -0.1, 0);
glEnd();
//green grass below
glColor3f(0.372, 0.407, 0.070);
glBegin(GL_QUADS);
glVertex3f(-1, -1, 0);
glVertex3f(1, -1, 0);
glVertex3f(1, -0.8, 0);
glVertex3f(-1, -0.8, 0);
glEnd();
//white lines on road
glColor3f(0.929, 0.850, 0.850);
glPointSize(5.0);
int factor = 10; GLushort pattern = 0x3333;
glEnable(GL_LINE_STIPPLE);
glLineStipple(factor, pattern);
glBegin(GL_LINES);
glVertex3f(1, -0.45, 0);
glVertex3f(-1, -0.45, 0);
glEnd();
glDisable(GL_LINE_STIPPLE);
glColor3f(0.929, 0.850, 0.850);
glPointSize(5.0);
glBegin(GL_LINES);
glVertex3f(1, -0.75, 0);
glVertex3f(-1, -0.75, 0);
glVertex3f(1, -0.15, 0);
glVertex3f(-1, -0.15, 0);
glEnd();
glPushMatrix();
glTranslatef(-0.8, 0.4, 0);
glScalef(0.5, 0.45, 0);
building(0, 0.17, 0.394);
glPopMatrix();
glPushMatrix();
glTranslatef(-0.35, 0.27, 0);
glScalef(0.55, 0.3, 0);
building(0.552, 0.266, 0.505);
glPopMatrix();
glPushMatrix();
//glLoadIdentity();
glTranslatef(0.2, 0.45, 0);
glScalef(1.2, 0.5, 0);
building(0.294, 0.337, 0.584);
glPopMatrix();
glPushMatrix();
glTranslatef(0.75, 0.27, 0);
glScalef(0.55, 0.3, 0);
building(0.309, 0.396, 0.427);
glPopMatrix();
//building bases
//car1
glPushMatrix();
glTranslatef(carMove, -0.2, 0);
glScalef(0.5, 0.5, 0.5);
car(0.65, 0, 0);
glPopMatrix();
glutSwapBuffers();
}
void pressKey(int key, int xx, int yy) {
switch (key) {
case GLUT_KEY_LEFT:
if (deltaAngle > 30)
break;
deltaAngle = -0.01f;
glutPostRedisplay();
break;
case GLUT_KEY_RIGHT: deltaAngle = 0.01f; break;
case GLUT_KEY_UP: deltaMove = 0.05f; break;
case GLUT_KEY_DOWN: deltaMove = -0.05f; break;
}
}
void releaseKey(int key, int x, int y) {
switch (key) {
case GLUT_KEY_LEFT:
case GLUT_KEY_RIGHT: deltaAngle = 0.0f; break;
case GLUT_KEY_UP:
case GLUT_KEY_DOWN: deltaMove = 0; break;
}
}
void main(int argc, char **argv)
{
glutInit(&argc, argv);
myInit();
glutDisplayFunc(display);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutIdleFunc(display);
glutSpecialFunc(pressKey);
glutSpecialUpFunc(releaseKey);
glEnable(GL_DEPTH_TEST);
glutMainLoop();
}
Note:
The texture mapping car and building code have been excluded for being too large but they work fine and I don't think that they're the problem. If you require the full working code then kindly let me know and I'll upload it. I've been stuck at this problem a while. Any help is appreciated
The issue is a Z-fighting issue.
To solve you issue you have to disable the Depth Test and draw the objects form the back to the front:
glEnable(GL_DEPTH_TEST)
Or you have to draw the object with a different z coordinates, which define the z order of the object.
Note, in view space the z axis points out of the viewport. So if the z coordinate of an object is greater than that of an other object, then the object is in front of the other object.
A perspective effect can only be achieved if the depth of the objects is different, so that object in the behind appear smaller, than that object which are closer to the point of view (eye position).
But you have to ensure that the objects are not clipped.
This mean the (view space) z distance of the object to the eye position (first 3 parameters of gluLookAt) has to be in between the near and far plane (last 2 parameters of gluPerspective).
gluUnProject find wrong coordinates. I have greed drawing on black background with cell dimension 1x1. I try to detect click in cells and I getting wrong coordinates (not 1 - 1).
I know that is OpenGL 1.1 old, bud I must use it. I don't good with it, most time I use 2.1 or 3.1.
Render code:
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluPerspective(45.0f, width() / (float)height(), 0.1f, 100.0f);
gluLookAt(m_camera->getX(), m_camera->getY(), m_camera->getZ(),
m_camera->getX(), m_camera->getY(), m_camera->getZ() - 1.0f,
0.0f, 1.0f, 0.0f);
glPushMatrix();
int i;
/*
* Render grid
*/
for(i = 0; i <= m_mapProperties->getWidth(); i++)
{
glm::vec3 position(i * m_mapProperties->getGridWidth(), 0.0f, 0.0f);
glm::vec3 scale(0.05f, m_mapProperties->getHeight() * m_mapProperties->getGridHeight(), 0.0f);
RenderUtil::render(position, scale);
}
for(i = 0; i <= m_mapProperties->getHeight(); i++)
{
glm::vec3 position(0.0f, i * m_mapProperties->getGridHeight(), 0.0f);
glm::vec3 scale(m_mapProperties->getWidth() * m_mapProperties->getGridWidth(), 0.05f, 0.0f);
RenderUtil::render(position, scale);
}
for(i = 0; i < m_width * m_height; i++)
if(m_map[i])
m_map[i]->render();
glPopMatrix();
Click code:
QPoint cursorPos = event->pos();
GLint viewport[4];
GLdouble modelview[16];
GLdouble projection[16];
glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
glGetDoublev(GL_PROJECTION_MATRIX, projection);
glGetIntegerv(GL_VIEWPORT, viewport);
GLfloat winX, winY, winZ = 0.0f;
GLdouble x, y, z;
winX = (float)cursorPos.x();
winY = (float)viewport[3] - (float)cursorPos.y();
glReadPixels(winX, winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ);
winZ = 0.0f;
winZ = -m_camera->getZ();
gluUnProject(winX, winY, winZ, modelview, projection, viewport, &x, &y, &z);
qDebug() << x
<< y;
glPopMatrix() is discarding your last matrix. glGetxxx() will return another matrix.
Having trouble drawing a heptagon in my OpenGL program. I want to draw a heptagon within a rectangle, so far I can draw the red rectangle but the heptagon isn't showing up.
I don't think I need to convert to degrees unless I wanted to rotate it right? Here is my code:
void CChildView::OnGLDraw(CDC* pDC)
{
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
int width, height;
GetSize(width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, // left
1.0, // right
0.0, // bottom
GLdouble(height) / GLdouble(width), // top
1.0, // near
-1.0); // far
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glColor3d(1., 0., 0.);
glBegin(GL_POLYGON); // Rectangle
glVertex2d(0.25, 0.25);
glVertex2d(0.75, 0.25);
glVertex2d(0.75, 0.75);
glVertex2d(0.25, 0.75);
glEnd();
glColor3d(1., 1., 1.);
int numPoints = 7; // Heptagon
double x, y;
double radius = 0;
double centerx = 0;
double centery = 0;
glBegin(GL_POLYGON);
for (int i = 0; i < numPoints; i++)
{
x = centerx + radius * sin(2.0*M_PI*i / numPoints);
y = centery + radius * cos(2.0*M_PI*i / numPoints);
glVertex2d(x, y);
}
glEnd();
glColor3d(0., 1., 0.);
glBegin(GL_LINES);
glVertex2d(m_linefmx, m_linefmx);
glVertex2d(m_linetox, m_linetoy);
glEnd();
}
The issue is that radius is initialized to 0 and never changed, so all points are calculated as (0,0).
I'm using code to draw text as textures in OpenGL (Qt4.8.3 + Linux (debian-like)).
Code was ported from 2D project, where it is working good.
2D project was using gluOrtho2D, now I use gluLookAt for 3D.
The issue is that instead of text I'm seing colored rectangle.
If I turn on GL_DEPTH_TEST I see artifacts instead of text. BTW artifacts change if I move camera, which is quite strange.
Here's the code:
void GLWidget::paintGL() {
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); //Set blending function.
glEnable(GL_BLEND); //Enable blending.
glShadeModel(GL_SMOOTH);
glEnable(GL_MULTISAMPLE);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glPushMatrix();
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
gluPerspective( 60.0f, (GLdouble) width() / (GLdouble) height(), 0.001f, 10000.0f );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
// Set up current camera
gluLookAt( cameraDistance * sin(cameraTheta * M_PI / 180) * cos(cameraPhi * M_PI / 180),
cameraDistance * sin(cameraTheta * M_PI / 180) * sin(cameraPhi * M_PI / 180),
cameraDistance * cos(cameraTheta * M_PI / 180),
0.0, 0.0, 0.0,
0.0, 0.0, 1.0);
glTranslatef(-4.5355, -4.5355, 0.0);
glPushMatrix();
// draw text labels
drawLabel(1, 0, 90, "1");
drawLabel(2, 0, 90, "2");
drawLabel(3, 0, 90, "3");
drawLabel(4, 0, 90, "4");
drawLabel(5, 0, 90, "5");
glPopMatrix();
glGetIntegerv(GL_VIEWPORT, viewport);
glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
glGetDoublev(GL_PROJECTION_MATRIX, projection);
glPopMatrix();
}
void GLWidget::drawLabel(float xpos, float ypos, float angle, char *txt) {
float labelHeight = 0.3;
float labelWidth = labelHeight / 2;
float margin = labelWidth / 10;
float len = (float) strlen(txt);
glPushMatrix();
glRotatef(-angle, 0, 0, -1);
glTranslatef(xpos, ypos, 0.0f);
glRotatef(angle, 0, 0, -1);
glScalef(1.0, -1.0, 1.0);
glTranslatef(- len * labelWidth / 2, -labelHeight / 2 + margin, 0.0f);
// background
glColor3f(0.0f, 0.0f, 0.0f);
glBegin(GL_QUADS);
glVertex3f(-margin, -margin, 0);
glVertex3f(len * labelWidth + margin, -margin, 0);
glVertex3f(len * labelWidth + margin, labelHeight + margin, 0);
glVertex3f(-margin, labelHeight + margin, 0);
glEnd();
// text
glColor3f(0.5f, 0.5f, 0.5f);
glEnable(GL_TEXTURE_2D);
glBindTexture( GL_TEXTURE_2D, glFont->getTextureID() );
glFont->drawText(labelWidth, labelHeight, txt);
glBindTexture(GL_TEXTURE_2D, 0);
glDisable(GL_TEXTURE_2D);
glPopMatrix();
}
void oglFont::drawText(GLfloat cw, GLfloat ch, char *txt)
{
glBegin(GL_QUADS);
//character location and dimensions
GLfloat cx = 0.0f;
GLfloat cy = 0.0f;
//calculate how wide each character is in term of texture coords
GLfloat dtx = float(c_width) / float(m_width);
GLfloat dty = float(c_height) / float(m_height);
for (char * c = txt; *c != 0; c++, cx += cw) {
int index = getCharIndex(c);
int row = index / c_per_row;
int col = index % c_per_row;
if (index < 0) {
//qDebug() << "glFont: Character outside of font! char: " << c;
}
// find the texture coords
GLfloat tx = float(col * c_width) / float(m_width);
GLfloat ty = float(row * c_height) / float(m_height);
glTexCoord2f(0, 0);
glVertex2f(cx, cy);
glTexCoord2f(1, 0);
glVertex2f(cx + cw, cy);
glTexCoord2f(1, 1);
glVertex2f(cx + cw, cy + ch);
glTexCoord2f(0, 1);
glVertex2f(cx, cy + ch);
}
glEnd();
}
The reason for the artifacts is Z fighting.
This problem can be solved by increasing the depth buffer precision OR by making the different objects further apart from each-other (the ones from drawlable ).
Also make sure that your generated text doesn't get culled by the far plane / near plane (maybe you generate the geometry very near the edges ? ).
It turns out that because texture was loaded in QGLWidget constructor, context was either not created or not set.
I moved texture loading in initializeGL() method and it works great.