Understanding opengl's (glut) resize - c

I'm reading the sample code for the bezier curve on the online version of opengl's tutorial.
I'm curious about how is resize being handled in the example cause I figure I might use it on my own version of this program , I placed my questions on its comments:
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h); // what's GLsizei? Why is it called inside glViewPort?
glMatrixMode(GL_PROJECTION); // is it necessary to reset the projection matrix?
glLoadIdentity();
if (w <= h) // is this calculation universal, could I use it on another program?
glOrtho(-5.0, 5.0, -5.0*(GLfloat)h/(GLfloat)w,
5.0*(GLfloat)h/(GLfloat)w, -5.0, 5.0);
else
glOrtho(-5.0*(GLfloat)w/(GLfloat)h,
5.0*(GLfloat)w/(GLfloat)h, -5.0, 5.0, -5.0, 5.0);
glMatrixMode(GL_MODELVIEW); // why do I set to GL_MODELVIEW at the end?
glLoadIdentity(); // why does it get a reset?
}
Full code:
#include <stdlib.h>
#include <GL/glut.h>
GLfloat ctrlpoints[4][3] = {
{ -4.0, -4.0, 0.0}, { -2.0, 4.0, 0.0},
{2.0, -4.0, 0.0}, {4.0, 4.0, 0.0}};
void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glShadeModel(GL_FLAT);
glMap1f(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, 4, &ctrlpoints[0][0]);
glEnable(GL_MAP1_VERTEX_3);
}
void display(void)
{
int i;
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_LINE_STRIP);
for (i = 0; i <= 30; i++)
glEvalCoord1f((GLfloat) i/30.0);
glEnd();
/* The following code displays the control points as dots. */
glPointSize(5.0);
glColor3f(1.0, 1.0, 0.0);
glBegin(GL_POINTS);
for (i = 0; i < 4; i++)
glVertex3fv(&ctrlpoints[i][0]);
glEnd();
glFlush();
}
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h); // what's GLsizei? Why is it called inside glViewPort?
glMatrixMode(GL_PROJECTION); // is it necessary to reset the projection matrix?
glLoadIdentity();
if (w <= h) // is this calculation universal, could I use it on another program?
glOrtho(-5.0, 5.0, -5.0*(GLfloat)h/(GLfloat)w,
5.0*(GLfloat)h/(GLfloat)w, -5.0, 5.0);
else
glOrtho(-5.0*(GLfloat)w/(GLfloat)h,
5.0*(GLfloat)w/(GLfloat)h, -5.0, 5.0, -5.0, 5.0);
glMatrixMode(GL_MODELVIEW); // why do I set to GL_MODELVIEW at the end?
glLoadIdentity(); // why does it get a reset?
}
void keyboard(unsigned char key, int x, int y)
{
switch (key) {
case 27:
exit(0);
break;
}
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (500, 500);
glutInitWindowPosition (100, 100);
glutCreateWindow (argv[0]);
init ();
glutDisplayFunc(display);
glutReshapeFunc(reshape); // el reshape funciona correctamente
glutKeyboardFunc (keyboard);
glutMainLoop();
return 0;
}

GLsizei is a type, not a function. Therefore, it's not being called; its being casted; it's converting an int into a GLsizei. It's basically an int, but it makes it clear that you're using it for a size (I think). (I'm a Python programmer, so this is a guess)
glMatrixMode(...);
This does not reset the matrix, unless it is followed by a glLoadIdentity() call. Instead, it sets the current target of OpenGL's matrix operations to the matrix specified. This way, OpenGL knows what matrix you're trying to affect.
I've seen that calcuation before in the OpenGL superbible (or at least something like it); why don't you talk yourself through it and see what it's deciding and why? (Hint (I think): it's trying to keep the viewport square to avoid stretching)
At the end, it sets it back to GL_MODELVIEW since that matrix handles transformations, like translation and rotation, which are used to position vertices onscreen. It should be reset every frame so that your code can assume that the coordinate plane is currently at (0,0); that simplifies calculations about where to translate to.
Also note that reshape is not called by OpenGL, but by GLUT. OpenGL is platform-independent and does not handle windowing; this is why you need GLUT.
If you're new to OpenGL, you should work through it from the beginning - later tutorials will assume this sort of knowledge.

Related

Animate rectangle height increase/decrease?

I want to know how can I make an animation that represents a rectangle with height increase/decrease in OpenGL. I know I'm supposed to use the glScale and glTranslate functions.
Below, I will attach the code that I've worked with so far, where I managed to apply a pretty basic transition of a rectangle.
#include <windows.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <stdlib.h>
static GLfloat trans = 0.0;
void init(void)
{
glClearColor(0.2, 0.2, 0.2, 0.2);
glShadeModel(GL_FLAT);
}
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
glTranslatef(0.0 , trans, 1.0);
glColor3f(1.0, 1.0, 1.0);
glRectf(-25.0, -25.0, 25.0, 25.0);
glPopMatrix();
glColor3f(0.0, 0.0, 1.0);
glRectf(-15.0, -15.0, 15.0, 15.0);
glutSwapBuffers();
}
void transLeft(void)
{
trans = trans - 0.05;
if (trans < -75)
trans = -75;
glutPostRedisplay();
}
void transRight(void)
{
trans = trans + 0.05;
if (trans > 75)
trans = 75;
glutPostRedisplay();
}
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-100.0, 100.0, -100.0, 100.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void mouse(int button, int state, int x, int y)
{
switch (button) {
case GLUT_LEFT_BUTTON:
if (state == GLUT_DOWN)
glutIdleFunc(transLeft);
break;
case GLUT_RIGHT_BUTTON:
if (state == GLUT_DOWN)
glutIdleFunc(transRight);
break;
default:
break;
}
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutMainLoop();
return 0;
}
So you want to have variable height rectangle (based on what?).
Yes glScale(1.0,zoom,1.0) placed directly before or after the line
glTranslatef(0.0 , trans, 1.0);
In your display(void) function will do this. Where zoom is holding your animation state and is starting with value zoom=1.0 and to change size you just increment/decrement like this: zoom*=1.025 or zoom/=1.025.
However its usually better to interchange your hard-coded rectangle vertexes with variable ones based on parameter or time or whatever you want to change this with. That way you can interpolate between min and max rectangle size with parameter without changing the matrices which might pose a problem with other objects if you not careful And also this way provides more convenient control of the animation. For example you have:
glRectf(-25.0, -25.0, 25.0, 25.0);
And want to animate it to size:
glRectf(-25.0, -35.0, 25.0, 35.0);
over time so you can do this like this:
add some global or static variables holding your rectangle sizes and position and animation state:
// x0, y0beg, y0end, x1,y1beg,y1end
float myrec[]={-25.0, -25.0, -35.0, 25.0, 25.0, 35.0};
float t=0.0; // parameter in range <0.0,1.0>
in display compute your rectangle actual coordinates and render
You can use linear interpolation like this:
glRectf(myrect[0],myrect[1]+((myrect[2]-myrect[1])*t),
myrect[3],myrect[4]+((myrect[5]-myrect[4])*t));
set you t for animation somewhere
Where depends on what you want to achieve... If you have timer or some call that si repeated again and again you can increment the t in it by some step for example:
t+=dt/T;
if (t>1.0) t=1.0; // use t=0.0; if you want to repeat the animation after it finishes
Where dt is the avg time your call is repeated with and T is the time of whole animation finish. I do not use GLUT so I just assume your Display is called repeatedly (for example 60 times per second) and want the animation to finish in 2 sec then:
// dt = 1.0/60
// T = 2.0
t+=(1.0/120.0);
if (t>1.0) t=1.0; // use t=0.0; if you want to repeat the animation after it
You can also use elapsed time (by measuring it by some OS or environment function you have at your disposal I usually use performance timer/counters on windows) from last call instead of dt.
If you have more of such rectangles you can encapsulate this to some function and simply call it with pointer to its myrect values and parameter t for example:
void draw_rect(float *myrec,float t)
{
glRectf(myrect[0],myrect[1]+((myrect[2]-myrect[1])*t),
myrect[3],myrect[4]+((myrect[5]-myrect[4])*t));
}
float rec0[]={-25.0, -25.0, -35.0, 25.0, 25.0, 35.0};
float rec1[]={-15.0, -15.0, -25.0, 15.0, 15.0, 25.0};
float t=0.0; // parameter in range <0.0,1.0>
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
glTranslatef(0.0 , trans, 1.0);
glColor3f(1.0, 1.0, 1.0);
draw_rect(rec0,t);
glPopMatrix();
glColor3f(0.0, 0.0, 1.0);
draw_rect(rec1,t);
glutSwapBuffers();
t+=(1.0/120.0);
if (t>1.0) t=0.0;
}

for loops and GLbegin

I am trying to make a Chaos Game in c using OpenGL and for some reason I am only creating a triangle and one point right now, when I am expecting to get 60,000 points. I think that this is because of the begin and end statements being inside of a for loop, and if not, then I'm not sure what is wrong. Any help solving the problem would be appreciated!
BTW the chaos game is where you start with one point, and then choose a random point on the triangle and then place a new point halfway between the chosen point and the original point and continue, and in my case I will repeat this 60,000 times. :)
void display(void)
{
glClear (GL_COLOR_BUFFER_BIT); //clears all pixels
int choice, i;
float x = 0.15, y = 0.85;
glColor3f (0.0, 0.0, 0.0); //this sets the drawing color to black
glBegin(GL_LINE_LOOP); //The triangle
glVertex3f(0.2, 0.2, 0.0);
glVertex3f(0.5, 0.8, 0.0);
glVertex3f(0.8, 0.2, 0.0);
glVertex3f(0.2, 0.2, 0.0);
glEnd();
glPointSize(3.0); //sets point size
glBegin(GL_POINTS); //this is the original point
glVertex3f(x, y, 0.0);
glEnd();
for(i=0; i<60,000; i++)
{
choice = (rand()%3);
switch(choice)
{
case 0:
x = (x + 0.5)/2; //this is the x1+x2/2 part of the midpoint theorem
y = (y + 0.8)/2; //this is the y1+y2/2 part of the midpoint theorem
glBegin(GL_POINTS);
glVertex3f(x, y, 0.0);
glEnd();
break;
case 1:
x = (x + 0.8)/2;
y = (y + 0.2)/2;
glBegin(GL_POINTS);
glVertex3f(x, y, 0.0);
glEnd();
break;
case 2:
x = (x + 0.2)/2;
y = (y + 0.2)/2;
glBegin(GL_POINTS);
glVertex3f(x, y, 0.0);
glEnd();
default:
break;
}
}
glFlush ();
}
void init (void)
{
glClearColor (1.0, 1.0, 1.0, 0.0); //this sets the background color to white
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (250, 250);
glutInitWindowPosition (100, 100);
glutCreateWindow(argv[0]);
init ();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
Try replacing 60,000 with 60000. In C, 60,000 evaluates to 0.
For more on the comma operator, see the Wikipedia entry on it.

What is the use of reshape() function in glut?

How is the reshape() function working in this code and how is it getting its parameter from glutReshapeFunc(reshape) without any parameter in reshape of glutReshapeFunc(reshape)?
What is the value of int x, int y in void keyboard (unsigned char key, int x, int y) function?
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
static int year = 0, day = 0;
void init(void)
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glShadeModel (GL_FLAT);
}
void display(void)
{
glClear (GL_COLOR_BUFFER_BIT);
glColor3f (1.0, 1.0, 1.0);
glPushMatrix();
glutWireSphere(1.0, 20, 16); /* draw sun */
glRotatef ((GLfloat) year, 0.0, 1.0, 0.0);
glTranslatef (2.0, 0.0, 0.0);
glRotatef ((GLfloat) day, 0.0, 1.0, 0.0);
glutWireSphere(0.2, 10, 8); /* draw smaller planet */
glPopMatrix();
glutSwapBuffers();
}
void reshape (int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}
void keyboard (unsigned char key, int x, int y)
{
switch (key) {
case `d':
day = (day + 10) % 360;
glutPostRedisplay();
break;
case `D':
day = (day - 10) % 360;
glutPostRedisplay();
break;
case `y':
year = (year + 5) % 360;
glutPostRedisplay();
break;
case `Y':
year = (year - 5) % 360;
glutPostRedisplay();
break;
default:
break;
}
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize (500, 500);
glutInitWindowPosition (100, 100);
glutCreateWindow (argv[0]);
init ();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}
It appears that the glutReshapeFunc() function takes a pointer to a function; presumably, in fact, it is declared as something somewhat similar to:
void glutReshapeFunc(void (*function)(int x, int y));
Similarly, glutDisplayFunc() takes another pointer to a function, and glutKeyboardFunc() also takes a pointer to a function. When a function is specified by name without the function call parentheses after it, it reduces to 'pointer to a function' (or you can think of a bare function name as a pointer to the function body, like a bare array name is a pointer to the start of the array).
You'd have to read the manual to discover the purpose of the x and y parameters to the keyboard() function. They aren't used by the code shown. They are likely the position of something, but which something is less than clear without reading the manual.
reshape and keyboard functions are used as so called callbacks. You're giving GLUT pointers to those functions, GLUT keeps those pointers and calls those function, with parameters, at the times as specified in the GLUT documentation.
About like that:
void (*display_callback)(void);
void (*reshape_callback)(int, int);
void (*keyboard_callback(unsigned char, int, int);
/* ... */
void eventloop(...)
{
while(...) {
if( keyboard_event )
keyboard_callback(keyboard_event->key, mouse_x, mouse_y);
if( window_reshaped )
reshape_callback(window->width, window->height);
if( needs_redraw )
display_callback();
}
}
Now regarding what's done in the reshape callback: Everything that's placed there in beginner tutorials is actually much better done in the display function. Setting the viewport, setting the projection I mean. Later you'll probably want to draw a HUD, some text or a minimap, or a split view. And once you've reached that point, a reshape function doing viewport and projection setup becomes a liability. So get rid of it now.
void display(void)
{
int const w = glutGet(GLUT_WINDOW_WIDTH);
int const h = glutGet(GLUT_WINDOW_HEIGHT);
glClear (GL_COLOR_BUFFER_BIT);
glColor3f (1.0, 1.0, 1.0);
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
glPushMatrix();
glutWireSphere(1.0, 20, 16); /* draw sun */
glRotatef ((GLfloat) year, 0.0, 1.0, 0.0);
glTranslatef (2.0, 0.0, 0.0);
glRotatef ((GLfloat) day, 0.0, 1.0, 0.0);
glutWireSphere(0.2, 10, 8); /* draw smaller planet */
glPopMatrix();
glutSwapBuffers();
}
I hope this will be a direct answer to this question.
The reshape function is a call back function which is called whenever size or shape of the application window changes. Reshape function takes 2 arguments,they are width and height of reshaped window. Mainly these parameters are used to set a new viewport.

Enlarging a cube and putting it into a 3D space

I've created a program to display a lined cube on a white canvas but I am unsure how to multiple that cube into lets say? 10 x 10.
Another question is how would I go about creating the same cube in a 3D space?
Here's my code:
void drawScene(void)
{
int i, j;
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0, 0.0, 0.0);
glLoadIdentity();
glTranslatef(0.0, 0.0, -25.0);
glutWireCube(5.0); // Box.
glColor3f(1.0, 0.0, 0.0);
for(i=5; i<5; i++)
{
for (j = -5; j < 5; j++)
{
glPushMatrix();
glTranslatef(i*5, j*5, -35.0);
glColor3f(1.0, 1.0, 0);
glutSolidCube(5.0);
glColor3f(0.0, 0.0, 1.0);
glutWireCube(5.0);
glPopMatrix();
}
}
glFlush();
}
void setup(void)
{
glClearColor(1.0, 1.0, 1.0, 0.0);
}
void resize (int w, int h)
{
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-10.0, 10.0, -10.0, 10.0, 10.0, 100.0);
glMatrixMode(GL_MODELVIEW);
}
void KeyInput(unsigned char key, int x, int y)
{
switch(key)
{
case 27:
exit(0);
break;
default:
break;
}
}
int main(int argc, char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(500,500); /* Size of the Program Window */
glutInitWindowPosition(100,100);
glutCreateWindow("Box.cpp");
setup();
glutDisplayFunc(drawScene);
glutReshapeFunc(resize);
glutKeyboardFunc(KeyInput);
glutMainLoop();
return 0;
}
The glu library has a lot of useful tidbits like gluLookAt( xfrom, yfrom, zfrom, xto, yto, zto, xup, yup, zup );
You can scale things using glScaled( factor ) / glScalef( factor )
You should poke around Google for some GL 1.X documentation.

fatal error C1083: Cannot open include file: 'aux.h': Permission denied

I copied the following code from OpenGL's Redbook (Chapter 4: Display Lists) into my editor (Visual Studio Express Edition 2008), named it list.c and got compilation error.
#include "aux.h"
#include <GL/gl.h>
#include <GL/glu.h>
GLuint listName = 1;
void myinit (void)
{
glNewList (listName, GL_COMPILE);
glColor3f(1.0, 0.0, 0.0);
glBegin (GL_TRIANGLES);
glVertex2f (0.0, 0.0);
glVertex2f (1.0, 0.0);
glVertex2f (0.0, 1.0);
glEnd ();
glTranslatef (1.5, 0.0, 0.0);
glEndList ();
glShadeModel (GL_FLAT);
}
void drawLine (void)
{
glBegin (GL_LINES);
glVertex2f (0.0, 0.5);
glVertex2f (15.0, 0.5);
glEnd ();
}
void display(void)
{
GLuint i;
glClear (GL_COLOR_BUFFER_BIT);
glColor3f(0.0, 1.0, 0.0);
for (i = 0; i < 10; i++)
glCallList (listName);
drawLine ();
glFlush ();
}
void myReshape(GLsizei w, GLsizei h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
gluOrtho2D (0.0, 2.0, -0.5 * (GLfloat) h/(GLfloat) w,
1.5 * (GLfloat) h/(GLfloat) w);
else
gluOrtho2D (0.0, 2.0 * (GLfloat) w/(GLfloat) h, -0.5,
1.5);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
int main(int argc, char** argv)
{
auxInitDisplayMode (AUX_SINGLE | AUX_RGBA);
auxInitPosition (0, 0, 400, 50);
auxInitWindow (argv[0]);
myinit ();
auxReshapeFunc (myReshape);
auxMainLoop(display);
}
Don't use not aux, nor glaux. They're too old. GLUT is much more easier, while many of people use SDL or SFML (they're more flexible and feature-full than GLUT). You should try SFML - it has lots of features inside, it's lightweight and portable. You should be satisfied using this one =)
Still if you wanna use GLUT, here are your problems:
glutInit() should be called before
any other operations
glutInitDisplayMode() and other
window functions must be called
before any drawing
operations
Here's some sample code:
#include <GL/glut.h >
// rendering function
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0,1.0,1.0);
glBegin (GL_LINES);
glVertex2f (0.0, 0.5);
glVertex2f (15.0, 0.5);
glEnd ();
glFlush();
}
// some initializations
void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}
int main(int argc, char **argv)
{
// initialize GLUT library
glutInit(&argc, argv);
// set display mode
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
// set initial window size
glutInitWindowSize(250,250);
// set initial window position
glutInitWindowPosition(100,100);
// create the window
glutCreateWindow("moofoo");
// do our initialization routines
init();
// set function which will be called each frame
glutDisplayFunc(display);
// enter main rendering loop
glutMainLoop();
return 0;
}
You need to include the Windows header file. Fix:
#include <windows.h>
#include <GL/gl.h>
#include <GL/glu.h>
// etc...
I have changed the code placing glutXxx functions instead of auxXxx ones. It compiles but doesn't run, I'd appreciate feedback here:
#include "GL/glut.h"
#include <stdio.h>
//#include <windows.h>
GLuint listName = 1;
void myinit (void)
{
glNewList (listName, GL_COMPILE);
glColor3f(1.0, 0.0, 0.0);
glBegin (GL_TRIANGLES);
glVertex2f (0.0, 0.0);
glVertex2f (1.0, 0.0);
glVertex2f (0.0, 1.0);
glEnd ();
glTranslatef (1.5, 0.0, 0.0);
glEndList ();
glShadeModel (GL_FLAT);
}
void drawLine (void)
{
glBegin (GL_LINES);
glVertex2f (0.0, 0.5);
glVertex2f (15.0, 0.5);
glEnd ();
}
void display(void)
{
GLuint i;
glClear (GL_COLOR_BUFFER_BIT);
glColor3f(0.0, 1.0, 0.0);
for (i = 0; i < 10; i++)
glCallList (listName);
drawLine ();
glFlush ();
}
void myReshape(GLsizei w, GLsizei h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
gluOrtho2D (0.0, 2.0, -0.5 * (GLfloat) h/(GLfloat) w,
1.5 * (GLfloat) h/(GLfloat) w);
else
gluOrtho2D (0.0, 2.0 * (GLfloat) w/(GLfloat) h, -0.5,
1.5);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
int main(int argc, char** argv)
{
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGBA);
glutInitWindowPosition (100, 100);
glutInitWindowPosition (100,100);
glutInit (&argc, argv);
myinit ();
glutDisplayFunc (display);
glutReshapeFunc (myReshape);
glutMainLoop();
}

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