当窗口以原始大小（640 x 480）使用时，此代码会正确绘制贝塞尔曲线，但在调整大小时会错误地呈现控制点。
单击鼠标功能：
if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
// Store where the user clicked, note Y is backwards.
abc[NUMPOINTS].setxy((float)x,(float)(SCREEN_HEIGHT - y));
NUMPOINTS++;
// Draw the red dot.
drawDot(x, SCREEN_HEIGHT - y);
我不明白如何处理坐标系。
为什么使用SCREEN_HEIGHT转换适用于640x480但不适用于其他窗口尺寸？如何实现普及？
在我自己的应用程序中，我一直在没有glutOrtho2d工作，只是使用每个X，Y的计算，但我已经读过这种方法更好。我很感激对它的详细解释。
修改后的代码：
/* bezier.cpp by detour@metalshell.com
*
* Create a bezier curve by defining the three points
* with your mouse.
*
* http://www.metalshell.com/
*
*/
#include <windows.h>
#include <math.h>
#include <gl/Gl.h>
#include <gl/Glu.h>
#include <gl/glut.h>
// CREEN_WIDTH = 640, SCREEN_HEIGHT=480;
int SCREEN_WIDTH=640;
int SCREEN_HEIGHT = 480;
// Keep track of times clicked, on 3 clicks draw.
int NUMPOINTS = 0;
// Point class to keep it a little cleaner.
class Point {
public:
float x, y;
void setxy(float x2, float y2) { x = x2; y = y2; }
const Point & operator=(const Point &rPoint) {
x = rPoint.x;
y = rPoint.y;
return *this;
}
};
Point abc[3];
void myInit() {
glClearColor(0.0,0.0,0.0,0.0);
glColor3f(1.0,0.0,0.0);
glPointSize(4.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,(float)SCREEN_WIDTH,0.0,(float)SCREEN_HEIGHT);
}
void drawDot(int x, int y) {
glBegin(GL_POINTS);
glVertex2i(x,y);
glEnd();
glFlush();
}
void drawLine(Point p1, Point p2) {
glBegin(GL_LINES);
glVertex2f(p1.x, p1.y);
glVertex2f(p2.x, p2.y);
glEnd();
glFlush();
}
// Calculate the next bezier point.
Point drawBezier(Point A, Point B, Point C, double t) {
Point P;
P.x = pow((1 - t), 2) * A.x + 2 * t * (1 -t) * B.x + pow(t, 2) * C.x;
P.y = pow((1 - t), 2) * A.y + 2 * t * (1 -t) * B.y + pow(t, 2) * C.y;
return P;
}
void myMouse(int button, int state, int x, int y) {
// If left button was clicked
if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
// Store where the user clicked, note Y is backwards.
//abc[NUMPOINTS].setxy((float)x,(float)(y));
abc[NUMPOINTS].setxy((float)x,(float)(SCREEN_HEIGHT - y));
// abc[NUMPOINTS] es un arreglo de objetos Point, su contraparte en Casteljau es
NUMPOINTS++;
// Draw the red dot.
drawDot(x, SCREEN_HEIGHT - y);
//drawDot(x, SCREEN_HEIGHT);
// If 3 points are drawn do the curve.
if(NUMPOINTS == 3) {
glColor3f(1.0,1.0,1.0);
// Draw two legs of the triangle
drawLine(abc[0], abc[1]);
drawLine(abc[1], abc[2]);
Point POld = abc[0];
/* Draw each segment of the curve. Make t increment in
smaller amounts for a more detailed curve. */
for(double t = 0.0;t <= 1.0; t += 0.1) {
Point P = drawBezier(abc[0], abc[1], abc[2], t);
drawLine(POld, P);
POld = P;
}
glColor3f(1.0,0.0,0.0);
NUMPOINTS = 0;
}
}
}
void myDisplay() {
glClear(GL_COLOR_BUFFER_BIT);
glFlush();
}
int main(int argc, char *argv[]) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(SCREEN_WIDTH,SCREEN_HEIGHT);
glutInitWindowPosition(100,150);
glutCreateWindow("Bezier Curve");
glutMouseFunc(myMouse);
glutDisplayFunc(myDisplay);
myInit();
glutMainLoop();
return 0;
}
原始代码：
/* bezier.cpp by detour@metalshell.com
*
* Create a bezier curve by defining the three points
* with your mouse.
*
* http://www.metalshell.com/
*
*/
#include <windows.h>
#include <math.h>
#include <gl/Gl.h>
#include <gl/Glu.h>
#include <gl/glut.h>
int SCREEN_HEIGHT = 480;
// Keep track of times clicked, on 3 clicks draw.
int NUMPOINTS = 0;
// Point class to keep it a little cleaner.
class Point {
public:
float x, y;
void setxy(float x2, float y2) { x = x2; y = y2; }
const Point & operator=(const Point &rPoint) {
x = rPoint.x;
y = rPoint.y;
return *this;
}
};
Point abc[3];
void myInit() {
glClearColor(0.0,0.0,0.0,0.0);
glColor3f(1.0,0.0,0.0);
glPointSize(4.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,640.0,0.0,480.0);
}
void drawDot(int x, int y) {
glBegin(GL_POINTS);
glVertex2i(x,y);
glEnd();
glFlush();
}
void drawLine(Point p1, Point p2) {
glBegin(GL_LINES);
glVertex2f(p1.x, p1.y);
glVertex2f(p2.x, p2.y);
glEnd();
glFlush();
}
// Calculate the next bezier point.
Point drawBezier(Point A, Point B, Point C, double t) {
Point P;
P.x = pow((1 - t), 2) * A.x + 2 * t * (1 -t) * B.x + pow(t, 2) * C.x;
P.y = pow((1 - t), 2) * A.y + 2 * t * (1 -t) * B.y + pow(t, 2) * C.y;
return P;
}
void myMouse(int button, int state, int x, int y) {
// If left button was clicked
if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
// Store where the user clicked, note Y is backwards.
abc[NUMPOINTS].setxy((float)x,(float)(SCREEN_HEIGHT - y));
NUMPOINTS++;
// Draw the red dot.
drawDot(x, SCREEN_HEIGHT - y);
// If 3 points are drawn do the curve.
if(NUMPOINTS == 3) {
glColor3f(1.0,1.0,1.0);
// Draw two legs of the triangle
drawLine(abc[0], abc[1]);
drawLine(abc[1], abc[2]);
Point POld = abc[0];
/* Draw each segment of the curve. Make t increment in
smaller amounts for a more detailed curve. */
for(double t = 0.0;t <= 1.0; t += 0.1) {
Point P = drawBezier(abc[0], abc[1], abc[2], t);
drawLine(POld, P);
POld = P;
}
glColor3f(1.0,0.0,0.0);
NUMPOINTS = 0;
}
}
}
void myDisplay() {
glClear(GL_COLOR_BUFFER_BIT);
glFlush();
}
int main(int argc, char *argv[]) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(640,480);
glutInitWindowPosition(100,150);
glutCreateWindow("Bezier Curve");
glutMouseFunc(myMouse);
glutDisplayFunc(myDisplay);
myInit();
glutMainLoop();
return 0;
}
答案 0 :(得分：2)
在使用640或480的代码中随处更改以使用SCREEN_WIDTH和SCREEN_HEIGHT。
即
gluOrtho2D(0.0,640.0,0.0,480.0);
=＆GT;
gluOrtho2D( 0.0,(float)SCREEN_WIDTH,0.0,(float)SCREEN_HEIGHT );
＆安培;
glutInitWindowSize(640,480);
=＆GT;
glutInitWindowSize( SCREEN_WDITH, SCREEN_HEIGHT );
这样，当您更改SCREEN_WIDTH或SCREEN_HEIGHT时，您不依赖于其他地方设置的某些值。我怀疑你的问题是因为你没有修改gluOrtho2D电话......
答案 1 :(得分：0)
您的代码中存在许多问题：