OpenGL 布雷森汉姆线
Posted
技术标签:
【中文标题】OpenGL 布雷森汉姆线【英文标题】:OpenGL Bresenham Line 【发布时间】:2016-01-26 14:05:41 【问题描述】:我有一个使用 opengl 绘制 Bresenham 线的基本代码。问题是最后它没有显示结果。只有一个窗口快速打开和关闭,没有任何其他错误。有人可以帮帮我吗?
#include <math.h>
#include <iostream>
#include <algorithm>
#include <GL\glew.h>
#include <GL\freeglut.h>
int ww = 600, wh = 400;
int xi, yi, xf, yf;
bool firstClick = true;
using namespace std;
void setPixel(int x, int y)
glColor3f(0.0, 0.0, 0.0); //Set pixel to black
glBegin(GL_POINTS);
glVertex2i(x, y); //Set pixel coordinates
glEnd();
glFlush(); //Render pixel
//Draw line if X distance is greater than Y
void bresenhamX(int x0, int y0, int x1, int y1, int dx, int dy)
int i, j, k;
i = 2 * dy - dx;
j = 2 * dy;
k = 2 * (dy - dx);
if (!(x0 < x1))
swap(x0, x1);
swap(y0, y1);
setPixel(x0, y0);
while (x0 < x1)
if (i < 0)
i += j;
else
if (y0 < y1)
++y0;
else
--y0;
i += k;
++x0;
setPixel(x0, y0);
//Draw line if X distance is lesser than Y
void bresenhamY(int x0, int y0, int x1, int y1, int dx, int dy)
int i, j, k;
i = 2 * dx - dy;
j = 2 * dx;
k = 2 * (dx - dy);
if (!(y0 < y1))
swap(x0, x1);
swap(y0, y1);
setPixel(x0, y0);
while (y0 < y1)
if (i < 0)
i += j;
else
if (x0 > x1)
--x0;
else
++x0;
i += k;
++y0;
setPixel(x0, y0);
//Called by mouse(), will call the appropriate function depending on the length of the X and Y axis
void bresenham(int x0, int y0, int x1, int y1)
int dx = abs(x1 - x0);
int dy = abs(y1 - y0);
if (dx >= dy)
bresenhamX(x0, y0, x1, y1, dx, dy);
else
bresenhamY(x0, y0, x1, y1, dx, dy);
//Calls Bresenham function when the mouse has traced a line
void mouse(int btn, int state, int x, int y)
if (btn == GLUT_LEFT_BUTTON)
if (firstClick)
xi = x;
yi = (wh - y);
firstClick = false;
else
xf = x;
yf = (wh - y);
bresenham(xi, yi, xf, yf);
firstClick = true;
// Keyboard input processing routine.
void keyInput(unsigned char key, int x, int y)
switch (key)
case 27: // Press escape to exit.
exit(0);
break;
default:
break;
// Drawing (display) routine.
void drawScene(void)
glClearColor(0.4, 0.7, 0.5, 1.0); // Set foreground color
glColor3f(0.2, 0.3, 0.3); // Clear screen to background color.
glClear(GL_COLOR_BUFFER_BIT); //Flush created objects to the screen, i.e., force rendering.
glFlush();
// OpenGL window reshape routine.
void setup()
glViewport(0, 0, ww, wh); // Set viewport size to be entire OpenGL window.
glMatrixMode(GL_PROJECTION); // Set matrix mode to projection.
glLoadIdentity(); // Clear current projection matrix to identity.
gluOrtho2D(0.0, (GLdouble)ww, 0.0, (GLdouble)wh); // Specify the orthographic (or perpendicular) projection, i.e., define the viewing box.
glMatrixMode(GL_MODELVIEW); // Set matrix mode to modelview.
// Main routine: defines window properties, creates window, registers callback routines and begins processing.
int main(int argc, char **argv)
glutInit(&argc, argv); // Initialize GLUT.
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); // Set display mode as single-buffered and RGB color.
glutInitWindowSize(ww, wh); // Set OpenGL window size.
glutInitWindowPosition(100, 100); // Set position of OpenGL window upper-left corner.
glutCreateWindow("Bresenham"); // Create OpenGL window with title.
glutDisplayFunc(drawScene); // Register display routine.
setup(); // Register reshape routine.
glutKeyboardFunc(keyInput); // Register keyboard routine.
glutMouseFunc(mouse); // Begin processing.
glutMainLoop();
return 0;
【问题讨论】:
【参考方案1】:-
在鼠标回调中存储离线开始/结束点并发出
glutPostRedisplay()
使用存储的信息在显示回调中画线
大家一起:
#include <algorithm>
#include <GL/glut.h>
int ww = 600, wh = 400;
int xi, yi, xf, yf;
bool firstClick = true;
using namespace std;
void setPixel(int x, int y)
glColor3f(0.0, 0.0, 0.0); //Set pixel to black
glBegin(GL_POINTS);
glVertex2i(x, y); //Set pixel coordinates
glEnd();
//Draw line if X distance is greater than Y
void bresenhamX(int x0, int y0, int x1, int y1, int dx, int dy)
int i, j, k;
i = 2 * dy - dx;
j = 2 * dy;
k = 2 * (dy - dx);
if (!(x0 < x1))
swap(x0, x1);
swap(y0, y1);
setPixel(x0, y0);
while (x0 < x1)
if (i < 0)
i += j;
else
if (y0 < y1)
++y0;
else
--y0;
i += k;
++x0;
setPixel(x0, y0);
//Draw line if X distance is lesser than Y
void bresenhamY(int x0, int y0, int x1, int y1, int dx, int dy)
int i, j, k;
i = 2 * dx - dy;
j = 2 * dx;
k = 2 * (dx - dy);
if (!(y0 < y1))
swap(x0, x1);
swap(y0, y1);
setPixel(x0, y0);
while (y0 < y1)
if (i < 0)
i += j;
else
if (x0 > x1)
--x0;
else
++x0;
i += k;
++y0;
setPixel(x0, y0);
//Called by mouse(), will call the appropriate function depending on the length of the X and Y axis
void bresenham(int x0, int y0, int x1, int y1)
int dx = abs(x1 - x0);
int dy = abs(y1 - y0);
if (dx >= dy)
bresenhamX(x0, y0, x1, y1, dx, dy);
else
bresenhamY(x0, y0, x1, y1, dx, dy);
//Calls Bresenham function when the mouse has traced a line
bool drawLine = false;
void mouse(int btn, int state, int x, int y)
if( btn == GLUT_LEFT_BUTTON && state == GLUT_UP )
if (firstClick)
xi = x;
yi = (wh - y);
firstClick = false;
drawLine = false;
else
xf = x;
yf = (wh - y);
firstClick = true;
drawLine = true;
glutPostRedisplay();
// Keyboard input processing routine.
void keyInput(unsigned char key, int x, int y)
switch (key)
case 27: // Press escape to exit.
exit(0);
break;
default:
break;
// Drawing (display) routine.
void drawScene(void)
glClearColor(0.4, 0.7, 0.5, 1.0); // Set foreground color
glColor3f(0.2, 0.3, 0.3); // Clear screen to background color.
glClear(GL_COLOR_BUFFER_BIT); //Flush created objects to the screen, i.e., force rendering.
if( drawLine )
bresenham(xi, yi, xf, yf);
glFlush();
// OpenGL window reshape routine.
void setup()
glViewport(0, 0, ww, wh); // Set viewport size to be entire OpenGL window.
glMatrixMode(GL_PROJECTION); // Set matrix mode to projection.
glLoadIdentity(); // Clear current projection matrix to identity.
gluOrtho2D(0.0, (GLdouble)ww, 0.0, (GLdouble)wh); // Specify the orthographic (or perpendicular) projection, i.e., define the viewing box.
glMatrixMode(GL_MODELVIEW); // Set matrix mode to modelview.
// Main routine: defines window properties, creates window, registers callback routines and begins processing.
int main(int argc, char **argv)
glutInit(&argc, argv); // Initialize GLUT.
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); // Set display mode as single-buffered and RGB color.
glutInitWindowSize(ww, wh); // Set OpenGL window size.
glutInitWindowPosition(100, 100); // Set position of OpenGL window upper-left corner.
glutCreateWindow("Bresenham"); // Create OpenGL window with title.
glutDisplayFunc(drawScene); // Register display routine.
setup(); // Register reshape routine.
glutKeyboardFunc(keyInput); // Register keyboard routine.
glutMouseFunc(mouse); // Begin processing.
glutMainLoop();
return 0;
【讨论】:
以上是关于OpenGL 布雷森汉姆线的主要内容,如果未能解决你的问题,请参考以下文章