OpenGL Coordinate system confusion
- by user146780
Maybe I set up GLUT wrong. Basically I want verticies to be reletive to their size in pixels.
Ex:right now if I create a hexagon, it hakes up the whole screen even though the units are 6.
#include <iostream>
#include <stdlib.h> //Needed for "exit" function
#include <cmath>
//Include OpenGL header files, so that we can use OpenGL
#ifdef __APPLE__
#include <OpenGL/OpenGL.h>
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
using namespace std;
//Called when a key is pressed
void handleKeypress(unsigned char key, //The key that was pressed
int x, int y) { //The current mouse coordinates
switch (key) {
case 27: //Escape key
exit(0); //Exit the program
}
}
//Initializes 3D rendering
void initRendering() {
//Makes 3D drawing work when something is in front of something else
glEnable(GL_DEPTH_TEST);
}
//Called when the window is resized
void handleResize(int w, int h) {
//Tell OpenGL how to convert from coordinates to pixel values
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION); //Switch to setting the camera perspective
//Set the camera perspective
glLoadIdentity(); //Reset the camera
gluPerspective(45.0, //The camera angle
(double)w / (double)h, //The width-to-height ratio
1.0, //The near z clipping coordinate
200.0); //The far z clipping coordinate
}
//Draws the 3D scene
void drawScene() {
//Clear information from last draw
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity(); //Reset the drawing perspective
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glBegin(GL_POLYGON); //Begin quadrilateral coordinates
//Trapezoid
glColor3f(255,0,0);
for(int i = 0; i < 6; ++i) {
glVertex2d(sin(i/6.0*2* 3.1415),
cos(i/6.0*2* 3.1415));
}
glEnd(); //End quadrilateral coordinates
glutSwapBuffers(); //Send the 3D scene to the screen
}
int main(int argc, char** argv) {
//Initialize GLUT
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
glutInitWindowSize(400, 400); //Set the window size
//Create the window
glutCreateWindow("Basic Shapes - videotutorialsrock.com");
initRendering(); //Initialize rendering
//Set handler functions for drawing, keypresses, and window resizes
glutDisplayFunc(drawScene);
glutKeyboardFunc(handleKeypress);
glutReshapeFunc(handleResize);
glutMainLoop(); //Start the main loop. glutMainLoop doesn't return.
return 0; //This line is never reached
}
How can I make it so that a polygon of
0,0
10,0
10,10
0,10
defines a polygon starting at the top left of the screen and is a width and height of 10 pixels?
Thanks
