Why are the angles calculated in c++ not accurate? - c++

Question

I wanted to write a turtle in c++, but the angles at the turn are not accurate.
I tried to create a Koch curve, but the result was bad
Hereis a larger picture of this, it looks like the angles are wrong
This is my program:
#include <windows.h>
#include <stdlib.h>
#include <malloc.h>
#include <memory.h>
#include <tchar.h>
#include "turtle.h"
#define MAX_LOADSTRING 100
// Global Variables:
#define HIBA_00 TEXT("Error:Program initialisation process.")
HINSTANCE hInstGlob;
int OwniCmdShow;
char szClassName[] = "WindowsApp";
HWND Form1;
LRESULT CALLBACK WndProc0(HWND, UINT, WPARAM, LPARAM);
RECT rc;
HDC hdcMem;
HBITMAP hbmMem, hbmOld;
HBRUSH hbrBkGnd;
HDC hdc;
PAINTSTRUCT ps;
void DB_prepare_puffer(void);
void DB_start_drawing(void);
void DB_end_drawing(void);
void draw(void);
void screen_clear(void);
void print(int n);
int depth = 4;
float length = 1000;
turtle t;
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("StdWinClassName");
MSG msg;
WNDCLASS wndclass0;
OwniCmdShow = iCmdShow;
hInstGlob = hInstance;
wndclass0.style = CS_HREDRAW | CS_VREDRAW;
wndclass0.lpfnWndProc = WndProc0;
wndclass0.cbClsExtra = 0;
wndclass0.cbWndExtra = 0;
wndclass0.hInstance = hInstance;
wndclass0.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass0.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass0.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass0.lpszMenuName = NULL;
wndclass0.lpszClassName = TEXT("WIN0");
if (!RegisterClass(&wndclass0))
{
MessageBox(NULL, HIBA_00, TEXT("Program Start"), MB_ICONERROR); return 0;
}
Form1 = CreateWindow(TEXT("WIN0"),
TEXT("Form1"),
(WS_OVERLAPPED | WS_SYSMENU | WS_THICKFRAME | WS_MAXIMIZEBOX | WS_MINIMIZEBOX),
0,
0,
1920,
1050,
NULL,
NULL,
hInstance,
NULL);
DB_prepare_puffer();
ShowWindow(Form1, OwniCmdShow);
UpdateWindow(Form1);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc0(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc_lokal;
PAINTSTRUCT ps_lokal;
switch (message) {
case WM_CREATE:
break;
case WM_MOUSEMOVE:
break;
case WM_ERASEBKGND:
return (LRESULT)1;
break;
case WM_PAINT:
hdc_lokal = BeginPaint(hwnd, &ps_lokal);
EndPaint(hwnd, &ps_lokal);
t.init();
draw();
break;
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProcW(hwnd, message, wParam, lParam);
break;
}
return NULL;
}
void DB_prepare_puffer(void)
{
GetClientRect(Form1, &rc);
hdc = GetDC(Form1);
hbmMem = CreateCompatibleBitmap(hdc, rc.right - rc.left, rc.bottom - rc.top);
}
void DB_start_drawing(void)
{
GetClientRect(Form1, &rc);
hdc = GetDC(Form1);
BeginPaint(Form1, &ps);
hdcMem = CreateCompatibleDC(hdc);
hbmOld = (HBITMAP)SelectObject(hdcMem, hbmMem);
hbrBkGnd = CreateSolidBrush(RGB(255, 255, 255));
FillRect(hdcMem, &rc, hbrBkGnd);
DeleteObject(hbrBkGnd);
}
void DB_end_drawing(void)
{
BitBlt(hdc, rc.left, rc.top, rc.right - rc.left, rc.bottom - rc.top, hdcMem, 0, 0, SRCCOPY);
SelectObject(hdcMem, hbmOld);
DeleteDC(hdcMem);
EndPaint(Form1, &ps);
}
void draw(void)
{
DB_start_drawing();
screen_clear();
int i = 0;
depth = 5;
length = 1200;
while (i < depth) {
length = length / 3;
i++;
}
t.right(270);
print(depth);
DB_end_drawing();
}
//************************
//clear screen
//************************
void screen_clear(void)
{
HBRUSH hBrush;
RECT rect;
HDC hdc;
hdc = hdcMem;
hBrush = CreateSolidBrush(RGB(255, 255, 255));
SelectObject(hdc, hBrush);
SetRect(&rect, 0, 0, 1500, 900);
FillRect(hdc, &rect, hBrush);
DeleteObject(hBrush);
}
void print(int m) {
int n = m;
if (n == 0) {
t.forward(length, hdcMem);
}
if (n != 0){
n -= 1;
print(n);
t.left(60);
print(n);
t.right(120);
print(n);
t.left(60);
print(n);
}
}
this is the turtle.h file:
#pragma once
#define _USE_MATH_DEFINES
#include "resource.h"
#include <windows.h>
#include <cmath>
class turtle {
public:
void init();
void right(double _angle);
void left(double _angle);
void forward(int distance, HDC hdc);
double angle = 0;
POINT pos;
protected:
private:
};
And this is the turtle.cpp:
#pragma once
#include "turtle.h"
void turtle::init()
{
pos.x = 40;
pos.y = 800;
angle = 0;
}
void turtle::left(double _angle) {
angle -= _angle;
}
void turtle::right(double _angle) {
angle += _angle;
}
void turtle::forward(int distance, HDC hdc) {
MoveToEx(hdc, pos.x, pos.y, NULL);
double cos_angle = cos(angle * M_PI / (double)180);
double sin_angle = sin(angle * M_PI / (double)180);
POINT endpoint;
endpoint.x = (0 - (double)distance * sin_angle) + pos.x;
endpoint.y = (0 + (double)distance * cos_angle) + pos.y;
LineTo(hdc, endpoint.x, endpoint.y);
pos = endpoint;
}
In Python, however, this code worked (essentially the same as the c++ code):
from turtle import *
color('blue', 'white')
speed(100000000)
penup()
back(600)
pendown()
begin_fill()
depth = 0
length = 300
i = 0
def print(n):
if n == 0:
forward(length )
if n != 0:
n -= 1
print(n)
left(60)
print(n)
right(120)
print(n)
left(60)
print(n)
i = 0
depth = 5
length = 300
while i < depth:
length = length / 3
i += 1
print(depth)
(Result)
I hope you can help me.
Thanks

Answer 1

It will work with this code because the previously calculated position is stored more accurately.
turtle.cpp:
#pragma once
#include "turtle.h"
void turtle::init()
{
pos.x = 40;
pos.y = 800;
angle = 0;
}
void turtle::left(double _angle) {
angle -= _angle;
}
void turtle::right(double _angle) {
angle += _angle;
}
void turtle::forward(double distance, HDC hdc) {
MoveToEx(hdc, pos.x, pos.y, NULL);
double cos_angle = cos(angle * M_PI / (double)180);
double sin_angle = sin(angle * M_PI / (double)180);
DPOINT endpoint;
endpoint.x = (0 - distance * sin_angle) + pos.x;
endpoint.y = (0 + distance * cos_angle) + pos.y;
LineTo(hdc, endpoint.x, endpoint.y);
pos = endpoint;
}
And insert this code to turtle.h:
`
typedef struct DPOINT {
double x;
double y;
};
`
And change the 'pos' variable type to 'DPOINT'