Smoke/Smoke.h

#include "pixelGameEngine.h"
#include <algorithm>

using namespace olc;

class Smoke{
    float riseSpd;
    std::vector<vf2d> points;
    std::vector<vf2d> uvs;
    std::vector<Pixel> cols;
    vf2d size;
    vf2d pos;
    float fadeSpd=1; //How much alpha to drop down per second.
    int freq=rand()%2+1;
    float alpha=128;
    public:
    Smoke(vf2d size, vf2d pos, float riseSpd=5.f, float fadeSpd=100)
    :size(size),riseSpd(riseSpd),fadeSpd(fadeSpd) {
        int ind=0;
        points.push_back({pos.x,pos.y});
        uvs.push_back({0,0});
        cols.push_back(Pixel(128,128,128,128));
        for (float i=0;i<2*M_PI;i+=2*M_PI/64) {
            points.push_back({sinf(i)*size.x+pos.x,cosf(i)*size.y+pos.y});
            uvs.push_back({0,0});
            cols.push_back(Pixel(128,128,128,128));
        }
        points.push_back(points[1]);
        uvs.push_back({0,0});
        cols.push_back(Pixel(128,128,128,128));
    };

    void update(float fElapsedTime) {
        alpha=std::clamp(alpha-fadeSpd*fElapsedTime,0.f,255.f);
        for (int i=0;i<points.size();i++) {
            points[i].y-=(riseSpd+rand()%1000/1000.0F*riseSpd*4)*fElapsedTime;
            cols[i].a=(int)alpha;
        }
    }

    void render(PixelGameEngine*engine) {
        engine->DrawPolygonDecal(nullptr,points,uvs,cols);
    }

    bool expired() {
        for (int i=0;i<cols.size();i++) {
            if (cols[i].a>0) {
                return false;
            }
        }
        return true;
    }
};