用OpenGL實現DDA畫線算法

#include <GL/GLUT.H>
#include <iostream>
#include <math.h>

using namespace std;

float xs = 0.0;
float ys = 0.0;
float xe = 0.0;
float ye = 0.0;

void LineDDA(int x0, int y0, int x1, int y1)
{
	float x = 0.0;
	float y = 0.0;
	float m = 0.0;
	float dx = x1 - x0;
	float dy = y1 - y0;
	if (dx != 0)
	{
		m = dy/dx;
		if (m <= 1 && m >= -1)
		{
			y = y0;
			for (x = x0; x <= x1; x++)
			{
				glVertex2i(x, int(y+0.5));
				y += m;
			}
		}
		if (m>1 || m<-1)
		{
			m = 1/m;
			x = x0;
			for (y=y0; y<=y1; y++)
			{
				glVertex2i(int(x+0.5), y);
				x += m;
			}
		}
	}
	else
	{
		int x = x0;
		int y = 0;
		y = (y0 <= y1) ? y0 : y1;
		int d = fabs((double) (y0 - y1));
		while (d >= 0)
		{
			glVertex2i(x, y);
			y++;
			d--;
		}
	}
}

void lineSegment()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(0.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	LineDDA(xs, ys, xe, ye);
	glEnd();
	glFlush();
}

int main(int argc, char *argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
	cout << "輸入線段起始和終點座標（範圍爲 0 - 500, 0-500）:";
	cin >> xs >> ys >> xe >> ye;
	glutInitWindowPosition(50, 100);
	glutInitWindowSize(500, 500);
	glutCreateWindow("DDA畫線算法");
	glClearColor(1.0, 1.0, 1.0, 1.0);
	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(0.0, 500, 0.0, 500.0);
	glutDisplayFunc(lineSegment);
	glutMainLoop();

	return 0;
}