c++快速开发例子--Canvas

最新推荐文章于 2024-11-05 21:25:38 发布

原创最新推荐文章于 2024-11-05 21:25:38 发布 · 838 阅读

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这篇博客介绍了如何在图形界面中创建一个动态旋转的多边形，并挑战将旋转图形变成能碰撞墙壁并反弹的球体。通过使用旋转角度、极坐标和椭圆绘制，作者展示了如何实现图形的平滑旋转，并探讨了碰撞检测的实现思路，为图形编程爱好者提供了有趣的实践项目。

//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop

#include "canmain.h"
#include "math.h"
#include <stdlib.h>
//---------------------------------------------------------------------------
#pragma resource "*.dfm"
TFormMain *FormMain;
//---------------------------------------------------------------------------
__fastcall TFormMain::TFormMain(TComponent* Owner)
: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TFormMain::FormCreate(TObject *Sender)
{
   Canvas->Pen->Color = clTeal;
   Rotation = 0;
   PointCount = MaxPoints;
   RotatePoints();
}
//---------------------------------------------------------------------
void __fastcall TFormMain::FormPaint(TObject *Sender)
{
   int centerX = ClientWidth / 2;
   int centerY = ClientHeight / 2;
   int radius = min(centerY, centerX);

   Canvas->Ellipse(0, 0, radius*2, radius*2);
   int i,j;
   for (i = 0; i < PointCount; i++) {
       for (j = i + 1; j < PointCount; j++) {
           Canvas->MoveTo(radius + floor(Points[i].X * radius),
               radius + floor(Points[i].Y * radius));
           Canvas->LineTo(radius + floor(Points[j].X * radius),
               radius + floor(Points[j].Y * radius));
       }
   }

   // A challenge: Turn the rotating figure into a ball that bounces off the
   // walls of the window. Don't forget the english (spin) on the ball should
   // pick up when bouncing off the wall...
}
//---------------------------------------------------------------------
void __fastcall TFormMain::FormResize(TObject *Sender)
{
   Invalidate();
}
//---------------------------------------------------------------------
void __fastcall TFormMain::Timer1Timer(TObject *Sender)
{
   RotatePoints();
   Invalidate();
}
//---------------------------------------------------------------------
void __fastcall TFormMain::RotatePoints()
{
   // NOTE: all figures are in radians
   const float M_2PI = 2 * M_PI; // 2 pi radians in a circle
   float StepAngle = M_2PI / PointCount; // angular distance between points

   Rotation += M_PI / 32; // Increment the angle of rotation of figure
   if (Rotation > StepAngle)
       Rotation -= StepAngle; // Keep rotation less than distance between points

   // The loop below has i walking through the Points array, while j walks
   // simultaneously through the angles to each point on the circle.
   // Incrementing j by StepAngle moves j to the next point on the circle with
   // no complicated arithmetic (everything has been set up in advance of the
   // loop). Initializing j with Rotation causes the entire figure to shift
   // clockwise a small amount.
   //
   int i;
   float j;
   for (i = 0, j = Rotation; i < PointCount; i++, j += StepAngle) {
       Points[i].X = cos(j); // These values will be multiplied by the
       Points[i].Y = sin(j); // current radius at display time.
   }
}
//---------------------------------------------------------------------