// ■多重振り子

#include "myWin.h"
#include <math.h>
#include <stdlib.h>
#define PI  3.14159265358979
#define XStart  35
#define YStart   5     // 図形の位置調整でここを変更している。
#define Num      50
typedef struct { //状態
  double dAlf, Alf, dTheta, Theta, X, Y;
} state;
typedef struct{
  double L, M, gByL;
} parameter;
double  g, dt, t;
int ID1,ID2;
state a[Num][2]; double F[Num];
parameter Pa;
double Myu;// 動粘性抵抗
double KFact;//伝達係数
int timerFlag;
static HDC hBuff; static HBITMAP hBM;
void genBitmap(HWND hw){
	HDC hdc=GetDC(hw); hBM=CreateCompatibleBitmap(hdc,550,550);
	hBuff=CreateCompatibleDC(hdc); SelectObject(hBuff,hBM);
	ReleaseDC(hw,hdc);
}
void clearBitmap(){
	SelectObject(hBuff,GetStockObject(NULL_PEN));
	PatBlt(hBuff,0, 0,450,450,WHITENESS);
}
void drawBall(double X1, double Y1){
	HPEN   hpen=CreatePen(PS_SOLID,2,0x00); SelectObject(hBuff,hpen);
	HBRUSH hbrush=CreateSolidBrush(0xCCCCCC)  ; SelectObject(hBuff,hbrush);
	int X=(int)(X1*6), Y=(int)(Y1*6);
	Ellipse(hBuff,X-3,Y-3,X+3,Y+3);
	DeleteObject(hbrush);DeleteObject(hpen);
}
void drawLine(double X1, double Y1,double X2, double Y2){
	HPEN   hpen=CreatePen(PS_SOLID,2,0x00); SelectObject(hBuff,hpen);
	int IX, IY;
	IX=(int)(X1*6);IY=(int)(Y1*6);	MoveToEx(hBuff,IX,IY,NULL);
	IX=(int)(X2*6);IY=(int)(Y2*6);	LineTo  (hBuff,IX,IY);
	DeleteObject(hpen);
}
void draw(){
	clearBitmap();	double X1 = XStart, Y1 = YStart, X2,Y2;
	for(int i=Num-1; i>=0;i--){
		double cosTH = cos(a[i][ID1].Theta), sinTH = sin(a[i][ID1].Theta);
		X2 = Pa.L * sinTH + X1;   Y2 = Pa.L * cosTH + Y1;
		drawLine(X1, Y1, X2, Y2); drawBall(X1,Y1);
		X1 = X2; Y1 = Y2;
	}
	drawBall(X2,Y2);
}
void initData(){
	Pa.L = 1; Pa.M = 0.1;  double TH = 30.0 * PI / 180;
	g = 9.8; dt = 0.05; Myu = 0.001;  KFact = 0.8;//KFact/Myu(0〜1)を変更してみよう
	for(int i=0; i<Num;i++){
		a[i][0].Theta = TH; a[i][0].dTheta = 0;
	}
	t = 0; ID1 = 0; ID2 = 1; draw();
}
void update(){
  t = t + dt;  double mG0 = 0, DMg = Pa.M * g, TH = 0;
  for(int i=0;i<Num;i++){
    mG0 = mG0 + DMg; F[i] = -mG0 * sin(a[i][ID1].Theta);
    a[i][ID2].dTheta =  a[i][ID1].dTheta +F[i] * dt; mG0 *= KFact;
  }
  TH = 0;
  for(int i=Num-1;i>=0; i--){
	  TH += a[i][ID1].dTheta;
	  a[i][ID2].dTheta *= (1 - Myu);
      a[i][ID2].Theta  = a[i][ID1].Theta+ a[i][ID2].dTheta* dt;
  }
  ID1 = ID2; ID2 = 1-ID2;draw();
}
void procPaint(HWND hw, WPARAM wp,LPARAM lp){
	PAINTSTRUCT ps;	HDC hdc=BeginPaint(hw, &ps);
	BitBlt(hdc, 0,0,450,450,hBuff,0,0,SRCCOPY);
	EndPaint(hw,&ps);
}
void procLButtonDown(HWND hw, WPARAM wp,LPARAM lp){
	SetTimer(hw,1,10,NULL);timerFlag=true;
	initData();	InvalidateRect(hw,NULL,TRUE);
}
void procCreate(HWND hw, WPARAM wp,LPARAM lp){
	SetWindowText(hw,TEXT("多重振り子"));
	MoveWindow(hw,0,0,450,450,TRUE);
	genBitmap(hw);clearBitmap();
    SetTimer(hw,1,10,NULL);timerFlag=true;
	initData();	InvalidateRect(hw,NULL,TRUE);
}
void procRButtonDown(HWND hw, WPARAM wp,LPARAM lp){
	if(timerFlag){ KillTimer(hw,1);initData();}
	else update();
	timerFlag= false; InvalidateRect(hw,NULL,TRUE);
}
void procTimer(HWND hw, WPARAM wp,LPARAM lp){
	update(); InvalidateRect(hw,NULL,TRUE);
}
LRESULT CALLBACK WndProc(HWND hw, UINT msg, WPARAM wp,LPARAM lp){
	switch(msg){
	case WM_DESTROY       : PostQuitMessage(0)         ; return 0;
	case WM_CREATE        : procCreate(hw,wp,lp)       ; return 0;
	case WM_PAINT         : procPaint(hw,wp,lp)        ; return 0;
	case WM_TIMER         : procTimer(hw,wp,lp)        ; return 0;
	case WM_LBUTTONDOWN   : procLButtonDown(hw,wp,lp)  ; return 0;
	case WM_RBUTTONDOWN   : procRButtonDown(hw,wp,lp)  ; return 0;
	}
	return DefWindowProc(hw,msg,wp,lp);
}