#include "GL\glut.h"
#include <math.h>

#define GL_PI 3.1415f

static GLfloat xRot = 0.0f;
static GLfloat yRot = 0.0f;

void RenderScene()
{
	GLfloat x, y, z, angle;

	glClear(GL_COLOR_BUFFER_BIT);
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
	glColor3f(0.0f, 1.0f, 0.0f);

	//しばらく後に解説
	glPushMatrix();
	glRotatef(xRot, 1.0f, 0.0f, 0.0f);
	glRotatef(yRot, 0.0f, 1.0f, 0.0f);

	glBegin(GL_LINES);
	z = 0.0f;
	for (angle = 0.0f; angle <= GL_PI; angle += (GL_PI / 20.0f))
	{
		x = 50.0f * cos(angle);
		y = 50.0f * sin(angle);
		glVertex3f(x, y, z);

		//180度移動して点を取得
		x = 50.0f * cos(angle+GL_PI);
		y = 50.0f * sin(angle+GL_PI);
		glVertex3f(x, y, z);
	}
	glEnd();
	glPopMatrix();
	glutSwapBuffers();
}
void controlKeys(int key, int x, int y)
{
	if (key == GLUT_KEY_UP)
		xRot -= 5.0f;

	if (key == GLUT_KEY_DOWN)
		xRot += 5.0f;

	if (key == GLUT_KEY_LEFT)
		yRot -= 5.0f;

	if (key == GLUT_KEY_RIGHT)
		yRot += 5.0f;

	if (key > 356.0f)
		xRot = 0.0f;

	if (key < -1.0f)
		xRot = 355.0f;

	if (key > 356.0f)
		yRot = 0.0f;

	if (key < -1.0f)
		yRot = 355.0f;

	glutPostRedisplay();
}
void ChangeSize(int w, int h)
{
	GLfloat nRange = 100.0f;

	if (h == 0) h = 1; //0除算を防ぐためのチェッカー

	glViewport(0, 0, w, h);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	if (w <= h) {
		GLfloat aspect = h / w;
		glOrtho(-nRange, nRange, -nRange * aspect, nRange*aspect, -nRange, nRange);
	}
	else
	{
		GLfloat aspect = w / h;
		glOrtho(-nRange * aspect, nRange * aspect, -nRange, nRange, -nRange, nRange);
	}
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

int main(int argc, char* argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowSize(800, 600);
	glutCreateWindow("Complex Line");
	glutReshapeFunc(ChangeSize);
	glutSpecialFunc(controlKeys);
	glutDisplayFunc(RenderScene);

	glutMainLoop();

	return 0;
}