axis.c

#include <GL/glut.h>

#define DEBUG 1

// display globals
unsigned int height = 400, width = 400;
int xmin = -100, xmax = 100, ymin = -100, ymax = 100, nearVal = 1, farVal = 100;
// camera globals
float x = 5.0f, y = 0.0f, z = 5.0f;

void init(void){
	glEnable(GL_DEPTH_TEST);
	glClearColor(1.0, 1.0, 1.0, 1.0);
}

void winReshapeFcn(GLint newWidth, GLint newHeight){
	height = newHeight;
	width = newWidth;	

	glViewport(0, 0, width, height);
	
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(xmin, xmax, ymin, ymax, nearVal, farVal);
}

void displayFcn(void){
	glClearColor(1.0, 1.0, 1.0, 1.0);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	gluLookAt(x, y, z,
				 0.0f, 0.0f,  0.0f,
				0.0f, 1.0f, 0.0f);

	// x-as RED
	glColor3f(1, 0, 0);
	glBegin(GL_LINE_STRIP);
		glVertex3f(0, 0, 0);
		glVertex3f(xmax, 0, 0);
	glEnd();
	glEnable(GL_LINE_STIPPLE);
	glLineStipple(1, 0xAAAA);
	glBegin(GL_LINE_STRIP);
		glVertex3f(0, 0, 0);
		glVertex3f(xmin, 0, 0);
	glEnd();
	glDisable(GL_LINE_STIPPLE);

	// y-as GREEN
	glColor3f(0, 1, 0);
	glBegin(GL_LINE_STRIP);
		glVertex3f(0, 0, 0);
		glVertex3f(0, ymax, 0);
	glEnd();
	glEnable(GL_LINE_STIPPLE);
	glLineStipple(1, 0xAAAA);
	glBegin(GL_LINE_STRIP);
		glVertex3f(0, 0, 0);
		glVertex3f(0, ymin, 0);
	glEnd();
	glDisable(GL_LINE_STIPPLE);

	// z-as BLUE
	glColor3f(0, 0, 1);
	glBegin(GL_LINE_STRIP);
		glVertex3f(0, 0, 0);
		glVertex3f(0, 0, farVal);
	glEnd();
	glEnable(GL_LINE_STIPPLE);
	glLineStipple(1, 0xAAAA);
	glBegin(GL_LINE_STRIP);
		glVertex3f(0, 0, 0);
		glVertex3f(0, 0, -farVal);
	glEnd();
	glDisable(GL_LINE_STIPPLE);

	glColor3f(1, 1, 0);
	//glutSolidSphere(5, 20, 20);	

	glFlush();
	return;
}

void processSpecialKeys(int key, int xx, int yy) {
	if(DEBUG)
		printf("processSpecialKeys()\n");

	float fraction = 0.1f;

	switch (key) {
		case GLUT_KEY_LEFT :
			x -= fraction;
			break;
		case GLUT_KEY_RIGHT :
			x += fraction;
			break;
		case GLUT_KEY_UP :
			z += fraction;
			break;
		case GLUT_KEY_DOWN :
			z -= fraction;
			break;
	}
	if(DEBUG)
		printf("x: %f - y: %f - z: %f\n", x, y, z);
	glutPostRedisplay();
	return;
}

int main(int argc, char* argv[]){
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);
	glutInitWindowPosition(100, 100);
	glutInitWindowSize(height, width);	
	glutCreateWindow("ballen");
	init();
// display
	glutDisplayFunc(displayFcn);
	glutReshapeFunc(winReshapeFcn);
// keyboard
	glutSpecialFunc(processSpecialKeys);

	glutMainLoop();
	return 0;
}