I was writing a program to draw a square in my XY plane and make it rotate 360 degree, but it is not working.
void setupRC()
{
glClearColor(0,0,1,1);
glColor3f(1,0,0);
}
void timerfunc(int value)
{
glutPostRedisplay();
glutTimerFunc(33, timerfunc ,1);
}
void RenderScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
static GLfloat rot = 0.0f,x =0.0f , y=10.0f , z=0.0f;
rot++;
x = 10 * cos(rot);
y = 10 * sin(rot);
glPushMatrix();
glRotatef(rot,0.0,1.0,0.0);
glBegin(GL_POLYGON);
glVertex3i(10,-10,0);
glVertex3i(10,10,0);
glVertex3i(-10,10,0);
glVertex3i(-10,-10,0);
glVertex3i(10,-10,0);
glEnd();
glPopMatrix();
glutSwapBuffers();
}
void ChangeSize(GLint w, GLint h)
{
if(h==0)
h = 1;
GLfloat aspectratio = (GLfloat)w/(GLfloat)h;
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0f, aspectratio, -1.0, 400.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
int main(int argc , char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
glutInitWindowSize(800,600);
glutInitWindowPosition(0,0);
glutCreateWindow("chelsea");
glutTimerFunc(33, timerfunc , 1);
setupRC();
glutDisplayFunc(RenderScene);
glutReshapeFunc(ChangeSize);
glutMainLoop();
return 0;
}
I get no output, just a blank screen.
gluPerspective(60.0f, aspectratio, -1.0, 400.0);
Looks wrong, the near clipping plane needs to be a positive number
You should really use glRotatef for rotating, because your code is wrong if you want a plane rotating around XY (x and y will be 0 for some values of rot and you'll get to see nothing at all).
And you should perhaps give your polygons a color using the glColor commands.
As JB said, your gluPerspective call seems wrong, too. See this link for a reference.
Related
I don't know if I did something wrong in my functions (maybe wrong parameters to glOrtho) and so the result is just wrong or if it's all normal as it would be.
In particular I have this situation:
I would like to have the green rect and all its inner content to take all the space of the window and not just a part of it (if you notice there are some empty spaces all around the main content: "the green rect").
Here there are my main functions:
#define HEXAGONAL_SHRINK 0.8655f
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(640, 480);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
glClearColor (0.0, 0.0, 0.0, 0.0);
glShadeModel (GL_FLAT);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutMainLoop();
return 0;
}
void reshape(int w, int h)
{
GLfloat aspect, dim;
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (s3hex->rows > s3hex->columns)
dim = s3hex->rows * 0.5f;
else
dim = s3hex->columns * 0.5f;
aspect = (GLfloat)w / (GLfloat)h;
if (w <= h)
glOrtho (-dim, dim, -dim/aspect, dim/aspect, 1.0, -1.0);
else
glOrtho (-dim*aspect, dim*aspect, -dim, dim, 1.0, -1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void display(void)
{
CALint i, j;
CALreal z, h, color;
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
glTranslatef(-(s3hex->columns*HEXAGONAL_SHRINK)/2.0f, s3hex->rows/2.0f, 0);
glScalef(HEXAGONAL_SHRINK, -1, 1);
for (i=0; i<s3hex->rows; i++)
for (j=0; j<s3hex->columns; j++)
{
z = calGet2Dr(s3hex,Q.z,i,j);
h = calGet2Dr(s3hex,Q.h,i,j);
if (h > 0)
{
color = (h - h_min) / (h_Max - h_min);
glColor3d(1,color,0);
glRecti(j, i, j+1, i+1);
}
else
if (z > 0)
{
color = (z - z_min) / (z_Max - z_min);
glColor3d(color,color,color);
glRecti(j, i, j+1, i+1);
}
}
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glColor3d(0,1,0);
glRectd(0,0,s3hex->columns, s3hex->rows);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glPopMatrix();
glutSwapBuffers();
}
P.S: If you need to know what's s3hex is, then you can see it as a normal matrix in which every cell contains a set of substates. Then in according to the value of these substates I set the colors for the rendering in the display func.
Everything seems normal to me.
Nothing guaranties that s3hex->columns and s3hex->rows will match your viewport size.
What you can do is to scale up the modelview to make the drawing fill your viewport.
Something along the lines of:
glScalef(viewportWidth / s3hex->columns, viewportHeight / s3hex->rows, 1);
Don't do this if s3hex->columns or s3hex->rows is zero.
I have this little program that is supposed to rotate a square in 2D. When I give it fixed vertexes, it works fine. But when I try to put it in motion, the square just starts to flash and blink and not really resemble a square at all. Everything looks good to me, so I must be missing something. Can anyone see it?
#include <stdio.h>
#include <math.h>
#include <glut/glut.h>
#define DEG_TO_RAD 0.017453
GLsizei ww, wh;
GLfloat theta;
void display()
{
//clear window
glClear(GL_COLOR_BUFFER_BIT);
//draw unit square polygon
glBegin(GL_POLYGON);
glVertex2f(sin(DEG_TO_RAD*theta), cos(DEG_TO_RAD*theta));
glVertex2f(-sin(DEG_TO_RAD*theta), cos(DEG_TO_RAD*theta));
glVertex2f(-sin(DEG_TO_RAD*theta), -cos(DEG_TO_RAD*theta));
glVertex2f(sin(DEG_TO_RAD*theta), -cos(DEG_TO_RAD*theta));
// glVertex2f(-0.5, -0.5);
// glVertex2f(-0.5, 0.5);
// glVertex2f(0.5, 0.5);
// glVertex2f(0.5, -0.5);
glEnd();
//flush gl buffers
glFlush();
}
void init() {
//set color to black
glClearColor(0.0, 0.0, 0.0, 0.0);
//set fill color to white
glColor3f(1.0, 1.0, 1.0);
//set up standard orthogonal view with clipping
//box as cube of side2 centered at origin
//this is default view and these statements could be removed
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-1.0, 1.0, -1.0, 1.0);
}
void myreshape(GLsizei w, GLsizei h) {
//adjust clipping window
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w<=h)
gluOrtho2D(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w, 2.0 * (GLfloat) h / (GLfloat) w);
else
gluOrtho2D(-2.0 * (GLfloat) w / (GLfloat) h, 2.0 * (GLfloat) w / (GLfloat) h, -2.0, 2.0);
glMatrixMode(GL_MODELVIEW);
//adjust viewport
glViewport(0, 0, w, h);
//set global size for use by drawing routine
ww = w;
wh = h;
}
void myidle() {
theta += 2.0;
if (theta > 360.0) theta -= 360.0;
glutPostRedisplay();
}
int main(int argc, char** argv)
{
theta = 0.0;
// initialize mode and open a window in upper-left corner of screen
// window title is name of program (arg[0])
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(500, 500);//Set the window size
glutInitWindowPosition(0, 0);
glutCreateWindow("rotating square");
glutDisplayFunc(display);
init();
glutReshapeFunc(myreshape);
glutIdleFunc(myidle);
glutMainLoop();
return 0;
}
Your vertex definitions just don't produce a square. Try the following:
glVertex2f(cos(DEG_TO_RAD*(theta + 135)), sin(DEG_TO_RAD*(theta + 135)));
glVertex2f(cos(DEG_TO_RAD*(theta + 45 )), sin(DEG_TO_RAD*(theta + 45 )));
glVertex2f(cos(DEG_TO_RAD*(theta - 45 )), sin(DEG_TO_RAD*(theta - 45 )));
glVertex2f(cos(DEG_TO_RAD*(theta - 135)), sin(DEG_TO_RAD*(theta - 135)));
The comment from Andon below your question is right. You should create the geometry (the vertices) only once and then rotate them by setting the matrix to ModelView and rotate with glRotatef(...). Recreating geometries on each render cycle is a wrong aproach.
This will be my first post on stackoverflow.
So, I'm making a simple program(VISUAL STUDIO 2012), using GLUT library. I basically try to display a torus, but instead I get a black screen.
#include<gl/glut.h>
#include<math.h>
GLfloat r=8;
GLint spin=0;
GLfloat light_position[]={0.0,0.0,0.0,1.0};
GLfloat ex,ey=0, ez, upx=0, upy=0, upz=0;
void init(){
glClearColor(1.0,1.0,1.0,1.0);
glShadeModel(GL_FLAT);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
}
void display(void){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_TEST);
glPushMatrix();
double sine = (float)sin((float)spin);
double cosine = (float)cos((float)spin);
ex=r*sine;
ez=r*cosine;
gluLookAt(ex,ey,-5.0,0,0,0,upx,upy,upz);
glColor3b(1.0,0,0);
glutSolidTorus(0.275,0.85,8,15);
glPopMatrix();
glFlush();
}
void reshape(int w, int h)
{
glViewport(0,0,(GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluPerspective(40.0, (GLfloat) w/(GLfloat) h, 1.0,20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glLightfv( GL_LIGHT0, GL_POSITION, light_position);
}
void mouse(int button, int state, int x, int y)
{
switch(button)
{
case GLUT_LEFT_BUTTON:
if( state == GLUT_DOWN){
spin = (spin+15)%360;
glutPostRedisplay();
}
break;
default:
break;
}
}
void main(int argc, char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_RGBA);
glutInitWindowSize(800,600);
glutInitWindowPosition(300,300);
glutCreateWindow("Light Rotating Torus");
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutMainLoop();
}
Can somebody modify it/give a hint, so it displays something?
Thanks
The most obvious problem is your UP vector. You set upx, upy and upz. That is not a valid up vector, try changing upy to 1.0f. Because of this, your torus was probably rendered out of screen.
Also, glClear doesn't take GL_DEPTH_TEST as a parameter.
Correct call should be:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
Because of this, your screen was not cleared and stayed black (while you set glClearColor to be white).
And lastly, main function should always return int, never void (though it doesn't change anything in your case)
The program should simulate a planet rotating around another planet.
I use gltranslatef to let the planet move around the bigger planet, but the problem is that the planet should hide when is over the bigger planet, because dz is -0.5.
But if I test the program I always see the red planet over the blue one.
Another problem I have: the planet rotates too fast, how do I slow it?
#include <OpenGL/OpenGL.h>
#include <GLUT/GLUT.h>
#include "utility.h"
GLfloat dx=0.0;
GLfloat dz=-0.5;
bool plus=true;
void init()
{
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glLoadIdentity();
glOrtho(-1, 1, -1, 1, -1, 1);
glEnable(GLUT_DEPTH);
}
void render()
{
glClearColor(BLACK);
glClear(GL_COLOR_BUFFER_BIT);
glColor4f(BLUE);
glutWireSphere(0.25, 100, 100);
glPushMatrix();
glLoadIdentity();
glTranslatef(-0.5+dx, 0.0, -dz);
glColor4f(RED);
glutWireSphere(0.05, 100, 100);
glPopMatrix();
glFlush();
}
void idle()
{
if(plus)
{
dx+=0.05;
}
else
{
dx-=0.05;
}
if(dx>=1.0)
{
dx=0.5;
plus=false;
}
else if(dx<=-0.0)
{
dx=0.0;
plus=true;
}
glutPostRedisplay();
}
int main(int argc, const char * argv[])
{
glutInit(&argc, (char**)argv);
glutInitWindowSize(500, 500);
glutInitWindowPosition(150, 150);
glutInitWindowPosition(0, 0);
glutCreateWindow("Simple");
glutIdleFunc(idle);
init();
glutDisplayFunc(render);
glutMainLoop();
return 0;
}
I haven't understood well how does the idle function work, why it gets called so many times? Can't I choose a time interval with which the idle function gets called?
More info: RED and BLUE are RGB floats, defined in the utility.h header file.
plus is a bool that is used to know if I have to decrease or increase dx.
Give this a shot:
#include <GL/glut.h>
double GetSeconds()
{
return glutGet(GLUT_ELAPSED_TIME) / 1000.0f;
}
void render()
{
glClearColor(0,0,0,0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glColor3ub(0,0,255);
glutWireSphere(0.25, 100, 100);
glPushMatrix();
glLoadIdentity();
static double prv = GetSeconds();
double cur = GetSeconds();
double delta = cur - prv;
prv = cur;
const float DEG_PER_SEC = 60.0f;
static float angle = 0.0f;
angle += DEG_PER_SEC * delta;
while( angle > 360 ) angle -= 360;
glPushMatrix();
glRotatef( angle, 0, 1, 0 );
glTranslatef( 0.5, 0, 0);
glColor3ub(255,0,0);
glutWireSphere(0.05, 100, 100);
glPopMatrix();
glutSwapBuffers();
}
void reshape(int w, int h)
{
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1, 1, -1, 1, -1, 1);
}
void timer(int extra)
{
glutPostRedisplay();
glutTimerFunc(16, timer, 0);
}
int main(int argc, const char * argv[])
{
glutInit(&argc, (char**)argv);
glutInitWindowSize(500, 500);
glutInitWindowPosition(150, 150);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow("Simple");
glutReshapeFunc(reshape);
glutTimerFunc(0, timer, 0);
glutDisplayFunc(render);
glEnable( GL_DEPTH_TEST );
glutMainLoop();
return 0;
}
Important parts:
Explicit glMatrixMode() calls
Calling glutInitDisplayMode() before glutCreateWindow()
Double-buffering requires glutSwapBuffers()
Clearing the depth buffer via GL_DEPTH_BUFFER_BIT
glEnable( GL_DEPTH_TEST )
glRotatef() for planet rotation
Timer-based animation
I'm trying to simulate a particle system using OpenGl but I can't get it to work, this is what I have so far:
#include <GL/glut.h>
int main (int argc, char **argv){
// data allocation, various non opengl stuff
............
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE );
glutInitWindowPosition(100,100);
glutInitWindowSize(size, size);
glPointSize (4);
glutCreateWindow("test gl");
............
// initial state, not opengl
............
glViewport(0,0,size,size);
glutDisplayFunc(display);
glutIdleFunc(compute);
glutMainLoop();
}
void compute (void) {
// change state not opengl
glutPostRedisplay();
}
void display (void) {
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_POINTS);
for(i = 0; i<nparticles; i++) {
// two types of particles
if (TYPE(particle[i]) == 1) glColor3f(1,0,0);
else glColor3f(0,0,1);
glVertex2f(X(particle[i]),Y(particle[i]));
}
glEnd();
glFlush();
glutSwapBuffers();
}
I get a black window after a couple of seconds (the window has just the title bar before that). Where do I go wrong?
LE: the x and y coordinates of each particle are within the interval (0,size)
Try to make these changes in your code:
move the Main function at the end of the file
glPoinSize call belongs to the Display function
then you should provide a function to handle resizing of the window glutReshapeFunc(reshape), something like this
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, (GLdouble) w, 0.0, (GLdouble) h);
}
glFlush is called from glutSwapBuffers function so you don't need it there
insert this code (after glutCreateWindow call) to set the initial position for the projection
glClearColor(0.2, 0.0, 0.0, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 10, 0.0, 10, -1.0, 1.0);