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edin-m/box2d_sdl2_example.cpp

Created September 11, 2020 17:52
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  1. edin-m created this gist Sep 11, 2020.
    214 changes: 214 additions & 0 deletions box2d_sdl2_example.cpp
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,214 @@

    //http://www.youtube.com/user/thecplusplusguy
    //The Box2D main program with SDL
    #include <iostream>
    #include <SDL2/SDL.h>
    #include <SDL2/SDL_image.h>
    #ifdef __APPLE__
    #include <OpenGL/gl.h>
    #else
    #include <GL/gl.h>
    #endif
    #include <Box2D/Box2D.h>

    const int WIDTH=640;
    const int HEIGHT=480;
    b2World* world;
    SDL_Surface* screen;
    SDL_Renderer* ren2;
    const float M2P=20;
    const float P2M=1/M2P;

    void putPixel(SDL_Surface* dest,int x,int y,int r,int g,int b)
    {
    // std::cout << x << " " << y << std::endl;
    // if(x>=0 && x<dest->w && y>=0 && y<dest->h)
    // ((Uint32*)dest->pixels)[y*dest->pitch/4+x]=SDL_MapRGB(dest->format,r,g,b);
    }

    void swapValue(int& a,int& b)
    {
    int tmp=a;
    a=b;
    b=tmp;
    }

    void drawLine(SDL_Surface* dest,int x0,int y0,int x1,int y1)
    {

    SDL_RenderDrawLine(ren2, x0, y0, x1, y1);

    // int tmp;
    // bool step;

    // step=abs(y1-y0)>abs(x1-x0);
    // if(step)
    // {
    // swapValue(x0,y0);
    // swapValue(x1,y1);
    // }

    // if(x0>x1)
    // {
    // swapValue(x1,x0);
    // swapValue(y1,y0);
    // }
    // float error=0.0;
    // float y=y0;
    // float roundError=(float)abs(y1-y0)/(x1-x0);
    // int ystep=(y1>y0 ? 1 : -1);
    // for(int i=x0;i<x1;i++)
    // {
    //// if(step)
    //// putPixel(dest,y,i,255,255,255);
    //// else
    //// putPixel(dest,i,y,255,255,255);
    // error+=roundError;
    // if(error>=0.5)
    // {
    // y+=ystep;
    // error-=1;
    // }
    // }
    }

    void rotateTranslate(b2Vec2& vector,const b2Vec2& center,float angle)
    {
    b2Vec2 tmp;
    tmp.x=vector.x*cos(angle)-vector.y*sin(angle);
    tmp.y=vector.x*sin(angle)+vector.y*cos(angle);
    vector=tmp+center;
    }


    b2Body* addRect(int x,int y,int w,int h,bool dyn=true)
    {
    b2BodyDef bodydef;
    bodydef.position.Set(x*P2M,y*P2M);
    if(dyn)
    bodydef.type=b2_dynamicBody;
    b2Body* body=world->CreateBody(&bodydef);

    b2PolygonShape shape;
    shape.SetAsBox(P2M*w/2,P2M*h/2);

    b2FixtureDef fixturedef;
    fixturedef.shape=&shape;
    fixturedef.density=1.0;
    body->CreateFixture(&fixturedef);

    }

    void drawSquare(b2Vec2* points,b2Vec2 center,float angle)
    {
    for(int i=0;i<4;i++)
    drawLine(screen,points[i].x*M2P,points[i].y*M2P,points[(i+1)>3 ? 0 : (i+1)].x*M2P,points[(i+1)>3 ? 0 : (i+1)].y*M2P);
    }


    void init()
    {
    world=new b2World(b2Vec2(0.0,9.81));
    addRect(WIDTH/2,HEIGHT-50,WIDTH,30,false);
    }

    void display()
    {
    // SDL_FillRect(screen,NULL,0);
    b2Body* tmp=world->GetBodyList();
    b2Vec2 points[4];
    while(tmp)
    {
    for(int i=0;i<4;i++)
    {
    points[i]=((b2PolygonShape*)tmp->GetFixtureList()->GetShape())->m_vertices[i];
    rotateTranslate(points[i],tmp->GetWorldCenter(),tmp->GetAngle());
    }
    drawSquare(points,tmp->GetWorldCenter(),tmp->GetAngle());
    tmp=tmp->GetNext();
    }
    }

    int xdmain(int argc,char** argv)
    {
    SDL_Init(SDL_INIT_EVERYTHING);
    // screen=SDL_SetVideoMode(640,480,32,SDL_SWSURFACE);
    SDL_Window *window;
    SDL_Surface *image;

    SDL_Init(SDL_INIT_EVERYTHING);

    SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "3");

    // create the window like normal
    Uint32 flags = SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN;
    window = SDL_CreateWindow("SDL2 Example", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, flags);

    ren2 = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

    Uint32 start;
    SDL_Event event;
    bool running=true;
    init();
    while(running)
    {
    start=SDL_GetTicks();
    while(SDL_PollEvent(&event))
    {
    switch(event.type)
    {
    case SDL_QUIT:
    running=false;
    break;
    case SDL_KEYDOWN:
    switch(event.key.keysym.sym)
    {
    case SDLK_ESCAPE:
    case SDLK_q:
    running=false;
    break;
    }
    break;
    case SDL_MOUSEBUTTONDOWN:
    addRect(event.button.x,event.button.y,20,20,true);
    break;

    }
    }

    SDL_Rect rect;
    rect.x = 50;
    rect.y = 50;
    rect.w = 10;
    rect.h = 10;

    // clr scr
    SDL_SetRenderDrawColor(ren2, 0, 0, 0, 255);
    SDL_RenderClear(ren2);

    // draw example
    SDL_SetRenderDrawColor(ren2, 255, 255, 255, 255);
    SDL_RenderDrawLine(ren2, 100, 100, 200, 100);
    SDL_RenderFillRect(ren2, &rect);



    display();







    SDL_RenderPresent(ren2);


    world->Step(1.0/30.0,8,3); //update
    // SDL_Flip(screen);
    // SDL_UpdateWindowSurface(window);
    if(1000.0/30>SDL_GetTicks()-start)
    SDL_Delay(1000.0/30-(SDL_GetTicks()-start));
    }
    SDL_Quit();
    }