AngleNorming/main.cpp

#define OLC_PGE_APPLICATION
#include "pixelGameEngine.h"

#if defined(__EMSCRIPTEN__)
#include <emscripten.h>
#define FILE_RESOLVE(url, file) emscripten_wget(url, file); emscripten_sleep(0)
#else
#define FILE_RESOLVE(url, file)
#endif

using namespace olc; 

const float PI = 3.14159f;

float angle_difference(float angle_1, float angle_2)
{
    angle_1=fmod(angle_1,2*PI);
    angle_2=fmod(angle_2,2*PI);
    float angle_diff = angle_1 - angle_2;

    if (angle_diff > PI)
      angle_diff -= 2*PI;
    else if (angle_diff < -PI)
      angle_diff += 2*PI;

    return -angle_diff;
}

class Object{
    public:
    float facing_dir;
    float rotation_spd;
    vd2d pos;
    vd2d size;
    Object(vd2d pos, vd2d size, float rotation_spd=100*(3.14159f/180.f), float facing_dir=0)
    :pos(pos),size(size),rotation_spd(rotation_spd),facing_dir(facing_dir) {}
    void draw(PixelGameEngine*pge) {
        pge->DrawCircle(pos,size.x);
        pge->DrawLine(pos,{(int)(pos.x+4*cos(facing_dir)),(int)(pos.y+4*sin(facing_dir))});
    }
};

// Override base class with your custom functionality
class Example : public olc::PixelGameEngine
{
public:
    Example()
    {
        // Name your application
        sAppName = "Rotation";
    }
    
public:
    Object*testRotationObj;
    bool OnUserCreate() override
    {
        testRotationObj = new Object({(double)ScreenWidth()/2,(double)ScreenHeight()/2},{8,8});
        return true;
    }
    
    bool OnUserUpdate(float fElapsedTime) override
    {
        Clear(BLACK);
        float diffAng = atan2f(GetMouseY()-testRotationObj->pos.y,GetMouseX()-testRotationObj->pos.x);
        float rotAngle=angle_difference(testRotationObj->facing_dir,diffAng);

        if (abs(rotAngle)>testRotationObj->rotation_spd*fElapsedTime) { //Prevents stuttering. Wait for an entire rotation speed amount to occur
            if (rotAngle>0) {
                testRotationObj->facing_dir+=testRotationObj->rotation_spd*fElapsedTime;
            } else {
                testRotationObj->facing_dir-=testRotationObj->rotation_spd*fElapsedTime;
            }
        }

        testRotationObj->draw(this);
        return true;
    }
    
};

int main()
{
    Example demo;
    if (demo.Construct(256, 240, 2, 2))
        demo.Start();
    return 0;
}