doublepend.cpp

主要介绍vc++6.0的编程过程

// DoublePend.cpp : Implementation of CDoublePend

#include "stdafx.h"
#include "DoublePendulum.h"
#include "DoublePend.h"

#include <math.h>

/////////////////////////////////////////////////////////////////////////////
// CDoublePend


void CDoublePend::Function( double *xx, double *f )
{
	double c, c0, c1, c10, x22, x33;

	// Gravity divided by the length.
	c = 9.8 / m_dLength;

	// Calculate motion vectors.
	c0 = cos( xx[0] ) * c;
	c1 = cos( xx[1] ) * c;
	c10 = cos( xx[1] - xx[0] );
	c = sin( xx[1] - xx[0] );

	// Calculate the positions.
	x22 = xx[2] * xx[2] * c;
	x33 = xx[3] * xx[3] * c;
	c = 9.0 / ( 16.0 - 9.0 * c1 * c10 );

	// Store the values.
	f[0] = xx[2];
	f[1] = xx[3];
	f[2] = ( 2.0 * x33 / 3.0 + c10 * x22 +
		c10 * c1 - 2.0 * c0 ) * c;
	f[3] = ( -8.0 * x22 / 3.0 - c10 * x33 +
		3.0 * c10 * c0 - 8.0 * c1 / 3.0 ) * c;

}

void CDoublePend::FillOval( HDC hDC, int nX, int nY,
	int nXR, int nYR, COLORREF cColor )
{
	HBRUSH hBrush, hOldBrush;
	HPEN hPen, hOldPen;

	// Create the brush, select it into the dc,
	// and remember the old brush.
	hBrush = CreateSolidBrush( cColor );
	hOldBrush = (HBRUSH) SelectObject( hDC, hBrush );

	// Create the pen, select it into the dc.
	// and remember the old pen.
	hPen = CreatePen( PS_SOLID, 1, RGB( 0, 0, 0 ) );
	hOldPen = (HPEN) SelectObject( hDC, hPen );

	// Draw the ellipse.
	Ellipse( hDC, nX - ( nXR / 2 ), nY - ( nYR / 2 ),
		nX + ( nXR / 2 ), nY + ( nYR / 2 ) );

	// Select the old brush and pen back
	// into the dc.
	SelectObject( hDC, hOldBrush );
	SelectObject( hDC, hOldPen );

	// Delete the GDI objects.
	DeleteObject( hPen );
	DeleteObject( hBrush );

}

void CDoublePend::DrawPend( HDC hDC, RECT& rc )
{

	// We're going to double buffer in
	// order to reduce the redraw flicker.
	HBITMAP hOldBitmap, hBitmap;
	// Create a dc for the off-screen buffer.
	HDC hWorkDC = CreateCompatibleDC( hDC );
	// Create the off-screen buffer.
	hBitmap = CreateCompatibleBitmap( hWorkDC,
		rc.right - rc.left, rc.bottom - rc.top );
	// Select the bitmap into the newly-created
	// dc and remember the bitmap that was
	// previously selected.
	hOldBitmap =
		(HBITMAP) SelectObject( hWorkDC, hBitmap );

	// Draw a rectangle to clear the buffer.
	Rectangle( hWorkDC, rc.left, rc.top, rc.right,
		rc.bottom );

	// Calculate the width, height, and midpoint.
	int nWidth = rc.right - rc.left;
	int nHeight = rc.bottom - rc.top;
	int nMidX = rc.left + ( nWidth / 2 );
	int nMidY = rc.top + ( nHeight / 2 );

	// Calculate the endpoints of the pendulum.
	int nCx1 = nMidX + (int) ( m_dLength * cos( x[0] ) );
	int nCy1 = nMidY + (int) ( m_dLength * sin( x[0] ) );
	int nCx2 = nCx1 + (int) ( m_dLength * cos( x[1] ) );
	int nCy2 = nCy1 + (int) ( m_dLength * sin( x[1] ) );

	// Draw the three pendulum ellipses.
	FillOval( hWorkDC, nMidX,
		nMidY, 7, 7, RGB( 0, 255, 0 ) );
	FillOval( hWorkDC, nCx1,
		nCy1, 11, 11, RGB( 0, 255, 0 ) );
	FillOval( hWorkDC, nCx2,
		nCy2, 11, 11, RGB( 0, 255, 0 ) );

	// Select a black stock pen into the dc.
	SelectObject( hWorkDC, GetStockObject( BLACK_PEN ) );
	// Move to the midpoint.
	MoveToEx( hWorkDC, nMidX, nMidY, NULL );
	// Draw the first segment.
	LineTo( hWorkDC, nCx1, nCy1 );
	// Draw the second segment.
	LineTo( hWorkDC, nCx2, nCy2 );

	// Draw the off-screen buffer to the visual screen.
	BitBlt( hDC, 0, 0, nWidth, nHeight, hWorkDC, 0, 0,
		SRCCOPY );
	// Select the old bitmap into the dc, delete the
	// newly-created bitmap and dc.
	SelectObject( hWorkDC, hOldBitmap );
	DeleteObject( hBitmap );
	DeleteDC( hWorkDC );

}

STDMETHODIMP CDoublePend::Update()
{
	double x1[4], f1[4], f2[4], f3[4], f4[4], hh, hhh;

	hh = h / 2.0;
	hhh = h / 6.0;

	for( int k=0; k<16; k++ ){
		int i;

		// Update the first point.
		Function( x, f1 );
		for( i=0; i<4; i++ )
			x1[i] = x[i] + hh * f1[i];

		// Update the second point.
		Function( x1, f2 );
		for( i=0; i<4; i++ )
			x1[i] = x[i] + hh * f2[i];

		// Update the third point.
		Function( x1, f3 );
		for( i=0; i<4; i++ )
			x1[i] = x[i] + h * f3[i];

		// Update the fourth point.
		Function( x1, f4 );
		for( i=0; i<4; i++ )
			x[i] += hhh * ( f1[i] + 2.0 * f2[i] +
				2.0 * f3[i] + f4[i] );

		}

	// Cause a window redraw.
	InvalidateRect( NULL, FALSE );
	UpdateWindow();

	return S_OK;
}

STDMETHODIMP CDoublePend::SetValue(double dValue)
{

	// Set the update rate value.
	h = dValue;

	return S_OK;
}