Question

我一直在努力在我的游戏中实现基于2D平铺的水。我开始让瓷砖出现在屏幕上等。我有一个绘图功能，可以绘制每种瓷砖类型。我遇到的问题是，当我调用此函数时，水的Tiles不会改变位置。这使我相信此代码无法正常运行。每个循环都会调用此代码。这应该更新所有水砖的质量。出于某种原因，没有任何事情发生。水停留在原来的位置。我的图块在tile类的向量中只是

Tiles()
{
    TileProp // the type of tile (GROUND,AIR,WATER)
    Mass
    NewMass
} 

void App::SimulateCompression()
{
float Flow = 0;
float remainingmass = 0;

int ID = 0;

//Calculate and apply flow for each block
for (int X = 0; X < MAP_WIDTH; X++)
{
    for(int Y = 0; Y < MAP_HEIGHT; Y++)
    {
        //Skip inert ground blocks
        if(TileList[ID].TileProp == TILE_GROUND) continue;

        //Custom push-only flow
        Flow = 0;
        remainingmass = TileList[ID].Mass;
        if(remainingmass <= 0) continue;

        //The block below this one
        if(TileList[Rect2Lin(TILE_SIZE,X,(Y-1))].TileProp != TILE_GROUND)
        {
            Flow = GetStableWaterState(remainingmass + TileList[Rect2Lin(TILE_SIZE,X,(Y-1))].Mass /*mass[x][y-1]*/) - TileList[Rect2Lin(TILE_SIZE,X,(Y-1))].Mass;
            if(Flow > MinFlow){Flow *= 0.5; /*leads to smoother flow*/}
            int tempA = Min(MaxSpeed, remainingmass);
            if(Flow > tempA){Flow = tempA;}
            if(Flow < 0){Flow = 0;}

            TileList[ID].NewMass -= Flow;
            TileList[Rect2Lin(TILE_SIZE,X,(Y-1))].NewMass += Flow;
            remainingmass -= Flow;
        }

        if(remainingmass <= 0) continue;

        //Left
        if(TileList[Rect2Lin(TILE_SIZE,(X - 1),Y)].TileProp != TILE_GROUND)
        {
            //Equalize the amount of water in this block and it's neighbour
            Flow = (TileList[ID].Mass - TileList[Rect2Lin(TILE_SIZE,(X - 1),Y)].Mass)/4;
            if(Flow > MinFlow){Flow *= 0.5;}
            if(Flow > remainingmass){Flow = remainingmass;}
            if(Flow < 0){Flow = 0;}

            TileList[ID].NewMass -= Flow;
            TileList[Rect2Lin(TILE_SIZE,(X - 1),Y)].NewMass += Flow;
            remainingmass -= Flow;
        }

        if(remainingmass <= 0) continue;

        //Right
        if(TileList[Rect2Lin(TILE_SIZE,(X + 1),Y)].TileProp != TILE_GROUND)
        {
            //Equalize the amount of water in this block and it's neighbour
            Flow = (TileList[ID].Mass - TileList[Rect2Lin(TILE_SIZE,(X + 1),Y)].Mass)/4;
            if(Flow > MinFlow){Flow *= 0.5;}

            if(Flow > remainingmass){Flow = remainingmass;}
            if(Flow < 0){Flow = 0;}

            TileList[ID].NewMass -= Flow;
            TileList[Rect2Lin(TILE_SIZE,(X + 1),Y)].NewMass += Flow;
            remainingmass -= Flow;
        }

        if(remainingmass <= 0) continue;

        //Up. Only compressed water flows upwards
        if(TileList[Rect2Lin(TILE_SIZE,X,(Y + 1))].TileProp != TILE_GROUND)
        {
            Flow = remainingmass - GetStableWaterState(remainingmass + TileList[Rect2Lin(TILE_SIZE,X,(Y + 1))].Mass);
            if (Flow > MinFlow){Flow *= 0.5;}

            int tempB = Min(MaxSpeed, remainingmass);
            if(Flow > tempB){Flow = tempB;}
            if(Flow < 0){Flow = 0;}

            TileList[ID].NewMass -= Flow;
            TileList[Rect2Lin(TILE_SIZE,X,(Y + 1))].NewMass += Flow;
            remainingmass -= Flow;
        }
        ID++;
    }
}

ID = 0;
//Copy the new mass values 
for (int X = 0; X < MAP_WIDTH; X++)
{
    for (int Y = 0; Y < MAP_HEIGHT; Y++)
    {
        TileList[ID].Mass = TileList[ID].NewMass;
        ID++;
    }
}

ID = 0;
for(int X = 0; X < MAP_WIDTH; X++)
{
    for(int Y = 0; Y < MAP_HEIGHT; Y++)
    {
        //Skip ground blocks
        if(TileList[ID].TileProp == TILE_GROUND) continue;

        //Flag/unflag water blocks
        if(TileList[ID].Mass > MinMass)
        {
            TileList[ID].TileProp = TILE_WATER;
        }else
        {
            TileList[ID].TileProp = TILE_AIR;
        }
        ID++;
    }
}

//Remove any water that has left the map
for(int X = 0; X < MAP_WIDTH; X++)
{
    TileList[X].Mass = 0;
    TileList[Rect2Lin(TILE_SIZE,X,MAP_HEIGHT - 1)].Mass = 0;

}

for(int Y = 0; Y < MAP_HEIGHT; Y++)
{
    TileList[Rect2Lin(TILE_SIZE,0,Y)].Mass = 0;
    TileList[Rect2Lin(TILE_SIZE,(MAP_WIDTH - 1),Y)].Mass = 0;
}

}

Answer 1

好的，所以ID会变为0，因为在ID命中之后34它只留下两个嵌套for循环...为什么会这样做？

//Calculate and apply flow for each block
for (int X = 0; X < MAP_WIDTH; X++)
{
    for(int Y = 0; Y < MAP_HEIGHT; Y++)
    {
        //Skip inert ground blocks
        if(TileList[ID].TileProp == TILE_GROUND) continue;

        ...

        ID++;
    }
}

TileList[34]可能是地砖。在这一点上，你反复击中第一个if（因为在循环结束时你永远不会到达ID++），直到你耗尽了for - 循环。

试试这个：

//Calculate and apply flow for each block
for (int X = 0; X < MAP_WIDTH; X++)
{
    for(int Y = 0; Y < MAP_HEIGHT; Y++)
    {
        int ID = Rect2Lin(TILE_SIZE,X,Y));

        //Skip inert ground blocks
        if(TileList[ID].TileProp == TILE_GROUND) continue;

        ...
    }
}

修改：

好的，这适用于我的系统：

#include <GL/glut.h> #include <vector> using namespace std; // simple Eigen::Matrix work-alike template< typename T > class Matrix { public: Matrix( const size_t rows, const size_t cols ) : mStride( cols ) , mHeight( rows ) , mStorage( rows * cols ) {} T& operator()( const size_t row, const size_t col ) { return mStorage[ row * mStride + col ]; } const T& operator()( const size_t row, const size_t col ) const { return mStorage[ row * mStride + col ]; } size_t rows() const { return mHeight; } size_t cols() const { return mStride; } private: vector< T > mStorage; size_t mStride; size_t mHeight; }; struct Cell { enum Type{ AIR, GROUND, WATER }; Cell() : mType( AIR ) , mMass( 0 ) , mNewMass( 0 ) {} Type mType; float mMass; float mNewMass; }; const float MaxMass = 1.0f; const float MinMass = 0.0001f; const float MaxCompress = 0.02f; const float MaxSpeed = 1.0f; const float MinFlow = 0.01f; //Take an amount of water and calculate how it should be split among two //vertically adjacent cells. Returns the amount of water that should be in //the bottom cell. float get_stable_state_b( float total_mass ) { if ( total_mass <= 1 ) { return 1; } else if ( total_mass < 2*MaxMass + MaxCompress ) { return (MaxMass*MaxMass + total_mass*MaxCompress)/(MaxMass + MaxCompress); } else { return (total_mass + MaxCompress)/2; } } template< typename T > T constrain( const T& val, const T& minVal, const T& maxVal ) { return max( minVal, min( val, maxVal ) ); } typedef Matrix< Cell > State; void stepState( State& cur ) { for( size_t y = 1; y < cur.rows()-1; ++y ) { for( size_t x = 1; x < cur.cols()-1; ++x ) { Cell& center = cur( y, x ); // Skip inert ground blocks if( center.mType == Cell::GROUND ) continue; // Custom push-only flow float Flow = 0; float remaining_mass = center.mMass; if( remaining_mass <= 0 ) continue; // The block below this one Cell& below = cur( y-1, x ); if( below.mType != Cell::GROUND ) { Flow = get_stable_state_b( remaining_mass + below.mMass ) - below.mMass; if( Flow > MinFlow ) { //leads to smoother flow Flow *= 0.5; } Flow = constrain( Flow, 0.0f, min(MaxSpeed, remaining_mass) ); center.mNewMass -= Flow; below.mNewMass += Flow; remaining_mass -= Flow; } if ( remaining_mass <= 0 ) continue; // Left Cell& left = cur( y, x-1 ); if ( left.mType != Cell::GROUND ) { // Equalize the amount of water in this block and it's neighbour Flow = ( center.mMass - left.mMass ) / 4; if ( Flow > MinFlow ) { Flow *= 0.5; } Flow = constrain(Flow, 0.0f, remaining_mass); center.mNewMass -= Flow; left.mNewMass += Flow; remaining_mass -= Flow; } if ( remaining_mass <= 0 ) continue; // Right Cell& right = cur( y, x+1 ); if ( right.mType != Cell::GROUND ) { // Equalize the amount of water in this block and it's neighbour Flow = ( center.mMass - right.mMass ) / 4; if ( Flow > MinFlow ) { Flow *= 0.5; } Flow = constrain(Flow, 0.0f, remaining_mass); center.mNewMass -= Flow; right.mNewMass += Flow; remaining_mass -= Flow; } if ( remaining_mass <= 0 ) continue; // The block above this one Cell& above = cur( y+1, x ); if( above.mType != Cell::GROUND ) { Flow = remaining_mass - get_stable_state_b( remaining_mass + above.mMass ); if( Flow > MinFlow ) { //leads to smoother flow Flow *= 0.5; } Flow = constrain( Flow, 0.0f, min(MaxSpeed, remaining_mass) ); center.mNewMass -= Flow; above.mNewMass += Flow; remaining_mass -= Flow; } } } for( size_t y = 0; y < cur.rows(); ++y ) { for( size_t x = 0; x < cur.cols(); ++x ) { cur( y, x ).mMass = cur( y, x ).mNewMass; } } for( size_t y = 0; y < cur.rows(); ++y ) { for( size_t x = 0; x < cur.cols(); ++x ) { Cell& center = cur( y, x ); if( center.mType == Cell::GROUND ) { center.mMass = center.mNewMass = 0.0f; continue; } if( center.mMass > MinMass ) { center.mType = Cell::WATER; } else { center.mType = Cell::AIR; center.mMass = 0.0f; } } } // Remove any water that has left the map for( size_t x = 0; x < cur.cols(); ++x ) { cur( 0, x ).mMass = 0; cur( cur.rows()-1, x ).mMass = 0; } for( size_t y = 0; y < cur.rows(); ++y ) { cur( y, 0 ).mMass = 0; cur( y, cur.cols()-1 ).mMass = 0; } } void showState( const State& state ) { glPolygonMode( GL_FRONT, GL_LINE ); glBegin( GL_QUADS ); glColor3ub( 0, 0, 0 ); for( size_t y = 0; y < state.rows(); ++y ) { for( size_t x = 0; x < state.cols(); ++x ) { glVertex2f( x+0, y+0 ); glVertex2f( x+1, y+0 ); glVertex2f( x+1, y+1 ); glVertex2f( x+0, y+1 ); } } glEnd(); glPolygonMode( GL_FRONT, GL_FILL ); glBegin( GL_QUADS ); for( size_t y = 0; y < state.rows(); ++y ) { for( size_t x = 0; x < state.cols(); ++x ) { if( state( y, x ).mType == Cell::AIR ) continue; float height = 1.0f; if( state( y, x ).mType == Cell::GROUND ) { glColor3ub( 152, 118, 84 ); } else { glColor3ub( 0, 135, 189 ); height = min( 1.0f, state( y, x ).mMass ); } glVertex2f( x+0, y ); glVertex2f( x+1, y ); glVertex2f( x+1, y + height ); glVertex2f( x+0, y + height ); } } glEnd(); } State state( 20, 20 ); void mouse( int button, int button_state, int x, int y ) { float pctX = (float)x / glutGet( GLUT_WINDOW_WIDTH ); float pctY = 1.0f - ( (float)y / glutGet( GLUT_WINDOW_HEIGHT ) ); size_t cellX = pctX * state.cols(); size_t cellY = pctY * state.rows(); Cell& cur = state( cellY, cellX ); if( button_state == GLUT_UP ) return; if( button == GLUT_LEFT_BUTTON ) { cur.mType = ( cur.mType == Cell::GROUND ? Cell::AIR : Cell::GROUND ); cur.mMass = cur.mNewMass = 0.0f; } if( button == GLUT_RIGHT_BUTTON ) { cur.mType = Cell::WATER; cur.mMass = cur.mNewMass = 1.0f; } } void display() { static bool firstTime = true; if( firstTime ) { firstTime = false; for( size_t y = 0; y < state.rows(); ++y ) { for( size_t x = 0; x < state.cols(); ++x ) { state( y, x ).mType = (Cell::Type)( rand() % 3 ); state( y, x ).mMass = 1.0f; state( y, x ).mNewMass = 1.0f; } } } glClearColor( 1, 1, 1, 1 ); glClear( GL_COLOR_BUFFER_BIT ); glMatrixMode( GL_PROJECTION ); glLoadIdentity(); glOrtho( 0, state.cols(), 0, state.rows(), -1, 1); glMatrixMode( GL_MODELVIEW ); glLoadIdentity(); stepState( state ); showState( state ); glutSwapBuffers(); } void timer(int extra) { glutPostRedisplay(); glutTimerFunc(16, timer, 0); } int main( int argc, char **argv ) { glutInit( &argc, argv ); glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE ); glutInitWindowSize( 640, 480 ); glutCreateWindow( "Cells" ); glutDisplayFunc( display ); glutMouseFunc( mouse ); glutTimerFunc(0, timer, 0); glutMainLoop(); return 0; }

用于瓷砖基础水的2D元胞自动机

1 个答案: