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Transferring (X,Y) to a position on an array[]

Paladin_VB
Paladin_VB asked
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Last Modified: 2010-04-01
Right I have a bitmap which I load into an array. and that array is used to draw a height map , the code for that is shown below.

I would like to know , how to transfer x,y cordinates to an index position in an array

ie.         OneDimensionarray[<corresponding value from x,y>]

Thank You,

Mark


//VMap contains the contents of a Loaded greyscale bitmap to turn into a heightmap
// the values are then used to draw a map      
 
           for (int i= 0 ; i < (Height-1); i++)
            {
 
                  glBegin(GL_TRIANGLE_STRIP);
                  glBindTexture(GL_TEXTURE_2D, MapTexture[0]);
 
                  Zoffset = Height/2;
                  Xoffset = -Width/2;
                  HScale = 10;
 
                  for (int j = 0;j < Width; j++)
                  {
 
 
                  glVertex3f(
                                     j,
                                    VMap[(i+1)*Width + (j)]/HScale,
                                    - (i+1));
 
 
                  glVertex3f(
                                    j,
                                    VMap[(i)*Width + j]/HScale,
                                    - i);      
 
                  } // end of 2nd for loop
 
                  glEnd();
            } // end of 1st for loop
Comment
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If OneDimensionArray is a container class of your own, you could override operator(), e. g. like that

class OneDimensionArray
{
    int height;
    int width;

    vector<GLfloat> v;

public:
   ...
    GLfloat operator() (int x, int y) const { return v[(x*width) + y]; }
};


If you have

    OneDimensionArray VMap(Width, Height);
    loadBitmap(VMAP, ...);

    ...

you can simplify expressions like

    VMap[(i+1)*Width + (j)]/HScale

by

    VMap(i+1, j)/HScale


Regards, Alex

   

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Author

Commented:
sorry OneDimensionArray isn't a container class, it jsuta  one dimensional array hehe
>>>> it jsuta  one dimensional array hehe

Why not:

class OneDimensionalArray : public vector<GLfloat>
{
    int height;
    int width;
public:
    OneDimensionalArray(int w, int h) : height(h), width(w) {}
    GLfloat operator() (int x, int y) const { return v[(x*width) + y]; }
   
};

That would do the job.

Regards, Alex

Author

Commented:
Sorry misread what you put , I apologise - great answer , that sorted it,

Thank you ,

Mark
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