I'm trying to use glutKeyboardFunc in OpenGL. But when I use this function in main it's giving me an error that No matching function for call to 'glutKeyboardFunc'. Why is it so?
#include<GLUT/glut.h>
#include<OpenGL/OpenGL.h>
#include<iostream>
using namespace std;
static void display(){
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-1.0, 1.0, -1.0, 1.0);
glClearColor(0.0, 0.0, 0.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.6, 1, 0.4);
glFlush();
}
void mykeypressed(char key, int x,int y){
}
int main(int argc, char * argv[]){
glutInit(&argc, argv);
glutInitWindowPosition(300, 300);
glutInitWindowSize(500, 500);
glutCreateWindow("ps4_1");
glutDisplayFunc(display);
glutKeyboardFunc(mykeypressed);
glutTimerFunc(10000, exit, 0);
glutMainLoop();
return 0;
}
The signature of glutKeyboardFunc is
void glutKeyboardFunc(void (*func)(unsigned char key, int x, int y));
// ^^^^^^^^
Your mykeypressed()'s first parameter is a char, not unsigned char. The two types are different.
Related
I have written the following code to print the Koch curve using OpenGL. But I am getting an inverted output. What modifications are required to invert the output in OpenGL? Also, is there any other formula to find the vertex coordinates of the equilateral triangle of the Koch curve?
#include<iostream>
#include<GL/glut.h>
#define COS 0.5
#define SIN 0.866
int x1=10,x2=550,y1=200,y2=200;
void myinit()
{
glClearColor(0.0,1.0,0.0,1.0);
glColor3f(0.0,0.0,1.0);
glPointSize(3.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0,640,0,480);
}
void koch(int x1, int y1, int x2, int y2, int m)
{
int x[5],y[5],xx,yy,lx,ly;
lx=(x2-x1)/3;
ly=(y2-y1)/3;
x[0]=x1;
y[0]=y1;
x[4]=x2;
y[4]=y2;
x[1]=x[0]+lx;
y[1]=y[0]+ly;
x[3]=x[0]+2*lx;
y[3]=y[0]+2*ly;
xx=x[3]-x[1];
yy=y[3]-y[1];
x[2]=xx*(COS)+yy*(SIN);
y[2]=-xx*(SIN)+yy*(COS);
x[2]=x[1]+x[2];
y[2]=y[1]+y[2];
if(m>0)
{
koch(x[0],y[0],x[1],y[1],m-1);
koch(x[1],y[1],x[2],y[2],m-1);
koch(x[2],y[2],x[3],y[3],m-1);
koch(x[3],y[3],x[4],y[4],m-1);
}
else
{
glBegin(GL_LINES);
glVertex2d(x[0],y[0]);
glVertex2d(x[1],y[1]);
glEnd();
glBegin(GL_LINES);
glVertex2d(x[1],y[1]);
glVertex2d(x[2],y[2]);
glEnd();
glBegin(GL_LINES);
glVertex2d(x[2],y[2]);
glVertex2d(x[3],y[3]);
glEnd();
glBegin(GL_LINES);
glVertex2d(x[3],y[3]);
glVertex2d(x[4],y[4]);
glEnd();
}
}
void display()
{
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_LINES);
koch(x1,y1,x2,y2,2);
glEnd();
glFlush();
}
int main(int argc, char ** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(640,480);
glutInitWindowPosition(10,10);
glutCreateWindow("Grllp");
glutDisplayFunc(display);
myinit();
glutMainLoop();
}
My operating system is mac. However, when I put this code into the Xcode compiler and run it. The console says "no matching function for call to 'glutDisplayFunc'".
#include "GLUT/glut.h"
void init(void)
{
glClearColor(1.0, 1.0, 1.0, 0.0);
glMatrixMode(GL_PROJECTION);
gluOrtho2D(0.0, 200.0, 0.0, 150.0);
}
void lineSegement(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINE);
glVertex2i(180, 15);
glVertex2i(10, 145);
glEnd();
glFlush();
}
int main (int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowPosition(50, 100);
glutInitWindowSize(400, 300);
glutCreateWindow("An Example OpenGL program");
init();
glutDisplayFunc(lineSegement());
glutMainLoop();
return 1;
}
glutDisplayFunc takes a function pointer as its argument. The syntax you are trying to use does not match that:
glutDisplayFunc(lineSegement());
In this statement, lineSegment() is a call to the lineSegment function, with the return value (which is void) being passed to glutDisplayFunc.
To pass the function pointer, you simply write the name of the function for glutDisplayFunc argument:
glutDisplayFunc(lineSegement);
I am trying this sample open gl program on my codelite ide.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/glut.h>
GLenum doubleBuffer;
GLint thing1, thing2;
static void Init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glClearAccum(0.0, 0.0, 0.0, 0.0);
thing1 = glGenLists(1);
glNewList(thing1, GL_COMPILE);
glColor3f(1.0, 0.0, 0.0);
glRectf(-1.0, -1.0, 1.0, 0.0);
glEndList();
thing2 = glGenLists(1);
glNewList(thing2, GL_COMPILE);
glColor3f(0.0, 1.0, 0.0);
glRectf(0.0, -1.0, 1.0, 1.0);
glEndList();
}
static void Reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
static void Key(unsigned char key, int x, int y)
{
switch (key) {
case '1':
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glutPostRedisplay();
break;
case '2':
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glutPostRedisplay();
break;
case 27:
exit(0);
}
}
static void Draw(void)
{
glPushMatrix();
glScalef(0.8, 0.8, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glCallList(thing1);
glAccum(GL_LOAD, 0.5);
glClear(GL_COLOR_BUFFER_BIT);
glCallList(thing2);
glAccum(GL_ACCUM, 0.5);
glAccum(GL_RETURN, 1.0);
glPopMatrix();
if (doubleBuffer) {
glutSwapBuffers();
} else {
glFlush();
}
}
static void Args(int argc, char **argv)
{
GLint i;
doubleBuffer = GL_FALSE;
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-sb") == 0) {
doubleBuffer = GL_FALSE;
} else if (strcmp(argv[i], "-db") == 0) {
doubleBuffer = GL_TRUE;
}
}
}
int main(int argc, char **argv)
{
GLenum type;
glutInit(&argc, argv);
Args(argc, argv);
type = GLUT_RGB | GLUT_ACCUM;
type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
glutInitDisplayMode(type);
glutInitWindowSize(300, 300);
glutCreateWindow("Accum Test");
Init();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Draw);
glutMainLoop();
}
Program compiles fine on my machine, when tried to run it just output press any key to continue and program exits after key is pressed.
What I am missing ?
What command line arguments have you passed? You have no choice but to use -db for reasons I will explain.
In Windows 7, you cannot draw a single-buffered window because the window manager makes a copy of the framebuffer when you swap buffers and that is what it displays (composites). Without swapping buffers, nothing will ever be displayed. This modern window system design prevents painting partially completed frames, but it mandates double-buffered rendering.
In fact, you should re-write your software so that it defaults to double-buffered rendering unless you specify a command line argument instead of the other way around. This issue affects other platforms besides modern Windows (Vista and newer).
I'm a complete novice in OpenGL and have started following a book on this topic. The first program that they demonstrate is the Sierpinski Gasket program. Here's what the code looks like in the book:
#include<GL/glut.h>
#include<stdlib.h>
void myinit()
{
//attributes
glClearColor(1.0,1.0,1.0,1.0);
glColor3f(1.0,0.0,0.0); //draw in red
//set up viewing
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,50.0,0.0,50.0);
glMatrixMode(GL_MODELVIEW);
}
void display()
{
GLfloat vertices[3][2]={{0.0,0.0},{25.0,50.0},{50.0,0.0}}; //triangle
GLfloat p[2]={7.5,5.0}; //arbitrary point
glClear(GL_COLOR_BUFFER_BIT); //clear the window
glBegin(GL_POINTS);
//Gasket Program
for(int i=0;i<5000;i++){
int j=rand()%3;
//compute points halfway between random vertex and arbitrary point
p[0]=(vertices[j][0]+p[0])/2;
p[1]=(vertices[j][1]+p[1])/2;
//plot the point
glVertex2fv(p);
}
glEnd();
glFlush();
}
int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(500,500);
glutInitWindowPosition(0,0);
glutCreateWindow("Sierpinski Gasket");
glutDisplayFunc(display);
myinit();
glutMainLoop();
return 0;
}
However, when I compile the program it only displays a window completely filled with white and nothing else. Why isn't the above code working the way it should?
Swap glFlush() for glutSwapBuffers():
#include<GL/glut.h>
void display()
{
glClearColor(1.0,1.0,1.0,1.0);
glClear(GL_COLOR_BUFFER_BIT); //clear the window
//set up viewing
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,50.0,0.0,50.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
GLfloat vertices[3][2]={{0.0,0.0},{25.0,50.0},{50.0,0.0}}; //triangle
GLfloat p[2]={7.5,5.0}; //arbitrary point
glColor3f(1.0,0.0,0.0); //draw in red
glBegin(GL_POINTS);
//Gasket Program
for(int i=0;i<5000;i++)
{
int j=rand()%3;
//compute points halfway between random vertex and arbitrary point
p[0]=(vertices[j][0]+p[0])/2;
p[1]=(vertices[j][1]+p[1])/2;
//plot the point
glVertex2fv(p);
}
glEnd();
glutSwapBuffers();
}
int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
glutInitWindowSize(500,500);
glutCreateWindow("Sierpinski Gasket");
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
glFlush() won't actually swap the back/front buffers requested by GLUT_DOUBLE. You need glutSwapBuffers() for that.
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);