openGL rendering glulookat - opengl

I rendered a triangle in the scene but now that I'm adding mouse navigation nothing seems to work anymore. So I deleted all the navigation stuff again to see what was wrong with my use of gluLookAt(). But even in a very simple case I dont see anything:
void GLScene::paintGL() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
//m_navigation.UpdateCamera();
gluLookAt(0 ,0 ,20,
0,0,-1,
0, -1, 0 );
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1,0,0);
glBegin(GL_POLYGON);
glVertex3f(0,0,0);
glVertex3f(0,100,0);
glVertex3f(100,0,0);
glEnd();
}

you messed up your object transformation matrices
correct code (untested)
void GLScene::paintGL() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0 ,0 ,20,
0,0,-1,
0, -1, 0 );
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1,0,0);
glBegin(GL_POLYGON);
glVertex3f(0,0,0);
glVertex3f(0,100,0);
glVertex3f(100,0,0);
glEnd();
}

Related

Create rotating sphere with longitude lines c++ opengl

I've started using OpenGL and I'm trying to create a wired sphere with colored longitude lines (like timezones) that rotates.
I'm trying to draw them using gluDisk-s and apply shifting in glRotatef func but I get following result (shown on images)
How can I fix it?
May be there is better way to do this?
The code I'm using:
void CreateDisk(int shift) {
quad = gluNewQuadric();
gluQuadricDrawStyle(quad, GLU_LINE);
glPushMatrix ();
glTranslatef (0., 0., 1.);
glRotatef(shift, 0, 1, 0);
glRotatef(count, 0, 1, 0);
gluDisk (quad, 0.5, .5, 50, 1);
glPopMatrix ();
}
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(30, aspect, .5, 50);
glMatrixMode(GL_MODELVIEW); //select the modelview matrix.
glLoadIdentity ();
gluLookAt(0,0,4,
0,0,0,
0,1,0);
glPushMatrix();
glColor3f(1, 0, 1);
CreateDisk(20);
glColor3f(1, 0, 0);
CreateDisk(60);
glPopMatrix();
glutSwapBuffers();
}
Currently it's creating two disks, that's for testing.
First screen Second screen

Unhandled exception on openGL text display

I am trying to draw text using openGL which will be displayed in a window, over a kinect camera image. The program can draw squares and other shapes fine, but when I call the method to draw the text, it crashes. It seems to be crashing on the
glutStrokeCharacter(font, c);
Everything else works and when I comment out just this line the program still runs fine. Below is a code snippet of how I try and draw the text.
void Button::DrawSquare(bool selected)
{
glEnable( GL_POINT_SMOOTH );
glLineWidth(7);
if (selected == true) glColor3f(0,1,0);
else glColor3f((123.0/255.0f),(205/255.0f),(237.0/255.0f));
glBegin(GL_LINE_LOOP);
glVertex2f(X, Y);
glVertex2f(X+length, Y);
glVertex2f(X+length, Y+width);
glVertex2f(X, Y+width);
glEnd();
glLineWidth(3);
glColor3f(0,0,0);
glBegin(GL_LINE_LOOP);
glVertex2f(X, Y);
glVertex2f(X+length, Y);
glVertex2f(X+length, Y+width);
glVertex2f(X, Y+width);
glEnd();
glLineWidth(4);
//Start drawing text
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
if (selected == true) glColor3f(0,1,0);
else glColor3f(1,1,0);
void *font = GLUT_BITMAP_TIMES_ROMAN_10;
glRasterPos2i(this->X+15,this->Y+35);
string s(*this->trackname);
for (string::iterator i = s.begin(); i != s.end(); ++i)
{
char c = *i;
glutStrokeCharacter(font, c);// <<-- Line that gives error
}
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glColor3f(255,255,255);
}
The drawing of the squares just before the text works fine.
Here is a minimal working example of how to render text using glutBitmapCharacter:
static const std::string text_to_render = "testing 1 2 3 4";
void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode( GL_PROJECTION );
glPushMatrix();
glLoadIdentity();
glMatrixMode( GL_MODELVIEW );
glPushMatrix();
glLoadIdentity();
glDisable( GL_DEPTH_TEST ); // disable to render text in front of anything else
glRasterPos2f(0, 0); // center of screen
glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
GLvoid * font = GLUT_BITMAP_TIMES_ROMAN_10;
glColor3f(1.0f, 0.0f, 0.0f);
for(char chr : text_to_render)
{
glutBitmapCharacter(font, chr);
}
glEnable(GL_DEPTH_TEST); // re-enable depth test
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glutSwapBuffers();
}
The only difference here is that I'm disabling OpenGL's GL_DEPTH_TEST and I'm loading the identity matrices after pushing the current matrices.
Let me know if this is of any help.

OpenGL Drawing Axis in Corner

I've been searching on how to draw an Indicator-Axis in my OpenGL scene. The project's nested in a Qt OpenGL widget, but I think the problem is independent of Qt.
I have found on here and forums from years ago that suggest storing the viewport and data, loading new ones for the botttom corner, apply my rotations and draw, then restore the matrices. This seems the most beneficial to me, but I'm guessing I'm still missing some critical info in my OpenGL knowledge.
For now I just have it drawing a red line from -x to x, so I expected to have a red square in the bottom left of the screen:
void GLWidget::drawAxis()
{
float tempPro[16];
float tempMod[16];
glGetFloatv(GL_PROJECTION_MATRIX, &tempPro[0]);
glGetFloatv(GL_MODELVIEW_MATRIX, &tempMod[0]);
glViewport(0, 0, 50, 50);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f, 1.0f, 0.1f, 20.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
glBegin(GL_LINES);
glColor3f(1.0f, 0.0f, 0.0f);
glEnable( GL_LINE_SMOOTH );
glLineWidth( 1.5 );
glVertex3f(-1000, 0, 0);
glVertex3f(1000, 0, 0);
glEnd();
glPopMatrix();
glViewport(0, 0, 960, 600);
glMatrixMode(GL_PROJECTION);
glLoadMatrixf(tempPro);
gluPerspective(45.0f, (960.0/600.0), 0.1f, 400.0f);
glMatrixMode(GL_MODELVIEW);
glLoadMatrixf(tempMod);
}
Instead I get nothing, just a large empty scene, and I'm unsure how to proceed. My paintGL is essentially:
void GLWidget::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
Camera.Render();
glTranslatef(0.0, 0.0, 0.0);
glBegin(GL_QUADS);
glColor3f(1.0f, 1.0f, 1.0f);
glVertex3f(50.0f, 0.0f, 50.0f);
glVertex3f(50.0f, 0.0f, -50.0f);
glVertex3f(-50.0f, 0.0f, -50.0f);
glVertex3f(-50.0f, 0.0f, 50.0f);
glEnd();
drawAxis();
}
Not calling the draw-axis function still gives me my plane, with it, I get a large blank scene. Am I missing something in how I'm implementing the drawAxis? Should I setup another camera for the function or something like that?
You can use glPushMatrix() and glPopMatrix() to save and restore the state of your Projection and ModelView matrices.
Your not setting up your ModelView matrix to anything useful.
Try something like this:
void GLWidget::drawAxis()
{
glViewport(0, 0, 50, 50);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
gluPerspective(45.0f, 1.0f, 0.1f, 20.0f);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
//This really has to come from your camera....
gluLookAt(10.0f,10.0f,10.0f, 0.0f,0.0f,0.0f, 0.0f,0.1f,0.0f);
glColor3f(1.0f, 0.0f, 0.0f);
glEnable( GL_LINE_SMOOTH );
glLineWidth( 1.5 );
glBegin(GL_LINES);
glVertex3f(-1000, 0, 0);
glVertex3f(1000, 0, 0);
glEnd();
//Restore View
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glViewport(0, 0, 960, 600);
}

How to draw multiple cubes in OpenGL

I want to draw several cubes using glutSolidCube in some points in space. The examples I have found just call glutSolidCube and it works, but the only way a cube gets drawn for me is if the line is enclosed in glBegin(GL_POLYGON), which isn't required in the examples I've seen, and I only get one cube instead of several. What I have is:
glColor3f(1, 0, 0);
glLoadIdentity();
glTranslatef(5,2,1);
glutSolidCube(1);
glLoadIdentity();
glTranslatef(10,8,0);
glutSolidCube(1);
glLoadIdentity();
glTranslatef(3,7,9);
glutSolidCube(1);
glLoadIdentity();
glTranslatef(1,4,6);
glutSolidCube(1);
When I run this nothing happens. I know there's not a problem with the points being outside my view because if I draw vertices at the same points, I can see them. As far as I can tell from the examples and documentation I've read, I'm not doing anything incorrect. Can someone tell me what I'm doing wrong or give me a snippet of code that draws multiple cubes?
Try this:
glColor3f(1, 0, 0);
glPushMatrix();
glTranslatef(5,2,1);
glutSolidCube(1);
glPopMatrix();
glPushMatrix();
glTranslatef(10,8,0);
glutSolidCube(1);
glPopMatrix();
glPushMatrix();
glTranslatef(3,7,9);
glutSolidCube(1);
glPopMatrix();
glPushMatrix();
glTranslatef(1,4,6);
glutSolidCube(1);
glPopMatrix();
Without re-setting the model view matrix with glLoadIdentity(). Note that to start with you need to call glOrtho() or glPerspective() to set the camera once.
#include <GL/glut.h>
void init()
{
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_COLOR_MATERIAL);
}
void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
double aspect = (double)viewport[2] / (double)viewport[3];
gluPerspective(60, aspect, 1, 100);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// move back a bit
glTranslatef( 0, 0, -35 );
static float angle = 0;
angle += 1.0f;
glPushMatrix();
glTranslatef(0,0,0);
glRotatef(angle, 0.1, 0.2, 0.5);
glColor3ub(255,0,255);
glutSolidCube(5);
glPopMatrix();
glPushMatrix();
glTranslatef(10,-10,0);
glRotatef(angle, 0.1, 0.2, 0.5);
glColor3ub(255,0,0);
glutSolidCube(5);
glPopMatrix();
glPushMatrix();
glTranslatef(10,10,0);
glRotatef(angle, 0.1, 0.2, 0.5);
glColor3ub(0,255,0);
glutSolidCube(5);
glPopMatrix();
glPushMatrix();
glTranslatef(-10,10,0);
glRotatef(angle, 0.1, 0.2, 0.5);
glColor3ub(0,0,255);
glutSolidCube(5);
glPopMatrix();
glPushMatrix();
glTranslatef(-10,-10,0);
glRotatef(angle, 0.1, 0.2, 0.5);
glColor3ub(255,255,0);
glutSolidCube(5);
glPopMatrix();
glutSwapBuffers();
}
void reshape(int w, int h)
{
glViewport(0, 0, w, h);
}
void timer(int extra)
{
glutPostRedisplay();
glutTimerFunc(16, timer, 0);
}
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitWindowSize(640,480);
glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
glutCreateWindow("CUBES");
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutTimerFunc(0, timer, 0);
init();
glutMainLoop();
return 0;
}

Opengl: 2d HUD over 3D

I have looked at some questions posted here on the matter and still cant work out why my 2d HUD appears but makes my 3d Rendered world disappear.
EDIT: It seems that the 2d scene is taking control of the entire screen so every now and then I can see the 3d scene glitching through the 2d scene. So even though I its only ment to be rendering a quad thats 10 x 10 pixels it renders this then blanks out the rest of the screen.
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(40.0,(GLdouble)x/(GLdouble)y,0.5,20.0);
glMatrixMode(GL_MODELVIEW);
glViewport(0,0,x,y);
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glTranslatef(0.0,-0.5,-6.0);
glPushMatrix();
..Draw some 3d stuff...
glPopMatrix();
// Start 2d
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, SCREEN_WIDTH, SCREEN_HEIGHT, 0, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glColor3f(0.0f, 255.0f, 1.0f);
glBegin(GL_QUADS);
glVertex2f(0.0, 0.0);
glVertex2f(10.0, 0.0);
glVertex2f(10.0, 10.0);
glVertex2f(0.0, 10.0);
glEnd();
Then I swap buffers
Here is the order of my code. Its like it makes the 3d space then makes the 2d space which in turn cancels out the 3d space.
Took a little while to figure it out, so just in case others have the same issues:
...After Drawing 3d Stuff...
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0.0, SCREEN_WIDTH, SCREEN_HEIGHT, 0.0, -1.0, 10.0);
glMatrixMode(GL_MODELVIEW);
//glPushMatrix(); ----Not sure if I need this
glLoadIdentity();
glDisable(GL_CULL_FACE);
glClear(GL_DEPTH_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0);
glVertex2f(0.0, 0.0);
glVertex2f(10.0, 0.0);
glVertex2f(10.0, 10.0);
glVertex2f(0.0, 10.0);
glEnd();
// Making sure we can render 3d again
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
//glPopMatrix(); ----and this?
...Then swap buffers...
:)
If you're overlaying a 2D ortho projection over 3D, you generally want to get the depth buffer out of the equation:
glDepthMask(GL_FALSE); // disable writes to Z-Buffer
glDisable(GL_DEPTH_TEST); // disable depth-testing
Of course, you'll want to reset these to their original values before doing your next 3D pass.
glViewport(0, 0, x, y); //You need to do this only once on viewport resize
//Setup for 3D
glMatrixMode(GL_PROJECTION);
glLoadIdentity;
gluPerspective(40.0, (GLdouble)x/(GLdouble)y, 0.5, 20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity;
glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BIT);
// ... Render 3D ...
//Setup for 2D
glMatrixMode(GL_PROJECTION);
glLoadIdentity;
glOrtho(0, SCREEN_WIDTH, SCREEN_HEIGHT, 0, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity;
glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BIT);
// ... Render 2D ...
SwapBuffers;
Note that there's no need to handle Push/Pop of matrixes if you render 2D completely on top of 3D.