Periodic Functions in C++

How to Simulate Sinusoidal Curves in C++

Periodic functions produce an infinite order of sinusoidal curves.
The sine function has the general form y = asinθ;
and the cosine function has the general form y = acosθ + c;
where θ is angle in radians and a is an arbitrary constant that heightens the curve.

Code to Animate a Graphic Object through a Periodic Curve in C++

To make a graphic (dot) travel by the equation of a sine / cosine function, continuously increment θ by some angle interval (in radians), and use the equation to get the corresponding y value; using any c that gives a satisfactory height.

Create a new class;
Call it PeriodicFunction.
Type out the adjoining C++ code for animating an image body through the path of a sine / cosine curve.

Note: To get a cosine curve animation, just replace sin with cos.

Facet class file

#include "stdafx.h"
#include "Facet.h"
#include "PeriodicFunction.h"

PeriodicFunction* pf_track;

/*
* Our custom class that interfaces between the parent window
* and the subsequent daemonstrator classes
*/
Facet::Facet(HWND hWnd, int window_width, int window_height)
{
    pf_track = new PeriodicFunction(hWnd, window_width, window_height);
}

/*
* This guy decorates buttons with colour and title text
*/
bool Facet::decorateButton(WPARAM wParam, LPARAM lParam) {
    // button glide calling
    if (wParam == 12321)
    {
        LPDRAWITEMSTRUCT lpDIS = (LPDRAWITEMSTRUCT)lParam;

        SetDCBrushColor(lpDIS->hDC, RGB(255, 192, 203));
        SelectObject(lpDIS->hDC, GetStockObject(DC_BRUSH));

        RECT rect = { 0 };
        rect.left = lpDIS->rcItem.left;
        rect.right = lpDIS->rcItem.right;
        rect.top = lpDIS->rcItem.top;
        rect.bottom = lpDIS->rcItem.bottom;

        RoundRect(lpDIS->hDC, rect.left, rect.top, rect.right, rect.bottom, 50, 50);
        // button text
        DrawText(lpDIS->hDC, TEXT("MOVE"), -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);

        return TRUE;
    }
    return FALSE;
}

/*
* Call the target class' draw method
*/
void Facet::informPaint() {
    pf_track->paint();
}

/*
* Say there is more than a single push button,
* this guy picks out the correct button that got clicked
* and calls the corresponding apt function
*/
bool Facet::actionPerformed(HWND hWnd, WPARAM wParam, LPARAM lParam)
{
    switch (LOWORD(wParam))
    {
    case 12321:
        pf_track->moveSinusoidal();
        return TRUE;
    default:
        return FALSE;
    }
}

Facet::~Facet()
{
    delete pf_track;
}

PeriodicFunction Header file

#pragma once

#define aWIDTH 10
#define aHEIGHT 10
#define PI 3.1415926535897932384626433832795

class PeriodicFunction
{
public:
    PeriodicFunction(HWND, int, int);
    virtual ~PeriodicFunction();
    void paint();
    void moveSinusoidal();
protected:
    HWND hWindow;
    HDC hdc;

    int window_width;
    int window_height;
    COLORREF ball_colour;
    int theta;
    int a; // constant
    int y;
    HPEN ball_pen;
    HBRUSH ball_brush;
};

C++ code for PeriodicFunction Class file

#include "stdafx.h"
#include "PeriodicFunction.h"
#include <math.h>

PeriodicFunction::PeriodicFunction(HWND hWnd, int window_width, int window_height)
{
    hWindow = hWnd; // save away window handle
    this->window_width = window_width; // save away window width
    this->window_height = window_height; // save away window width

    ball_colour = RGB(255, 0, 0);
    theta = 0;
    a = 100; // constant

    // convert theta from degree to radians (work in a little translate for y)
    y = (int)round(a * sin(theta * (long double)PI / 180)) + int(window_height / 2);

    // Pen and brush for travelling ball
    ball_pen = CreatePen(PS_SOLID, 1, RGB(0, 0, 0));
    ball_brush = CreateSolidBrush(ball_colour);

    hdc = GetDC(hWindow);

    SelectObject(hdc, ball_pen); // select ball pen colour
    SelectObject(hdc, ball_brush); // select ball brush colour

    // draw a second demarcation line
    MoveToEx(hdc, 0, 80, NULL);
    LineTo(hdc, window_width, 80);

    // draw x-axis
    MoveToEx(hdc, 0, int(window_height/2 + aHEIGHT/2), NULL);
    LineTo(hdc, window_width, int(window_height/2 + aHEIGHT/2));
}

/*
* draws the ball/circle using the apt color
*/
void PeriodicFunction::paint() {
    // draw a dot
    Ellipse(hdc, theta, y, theta + aWIDTH, y + aHEIGHT);
}

void PeriodicFunction::moveSinusoidal() {
    // condition for continuing motion
    while (theta + aWIDTH < window_width) {
        // work in a little translate for y
        y = (int)round(a * sin(theta * (long double)PI / 180)) + int(window_height / 2);
        paint();

        theta += 15;
        // introduce a delay between renderings
        Sleep(50);
    }
}

PeriodicFunction::~PeriodicFunction()
{
    DeleteObject(ball_pen);
    DeleteObject(ball_brush);

    ReleaseDC(hWindow, hdc);
}

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