Window to Viewport Transformation is the process of transforming a 2D world-coordinate objects to device coordinates. Objects inside the world or clipping window are mapped to the viewport which is the area on the screen where world coordinates are mapped to be displayed.
- World coordinate – It is the Cartesian coordinate w.r.t which we define the diagram, like Xwmin, Xwmax, Ywmin, Ywmax
- Device Coordinate –It is the screen coordinate where the objects is to be displayed, like Xvmin, Xvmax, Yvmin, Yvmax
- Window –It is the area on world coordinate selected for display.
- ViewPort –It is the area on device coordinate where graphics is to be displayed.
Mathematical Calculation of Window to Viewport:
It may be possible that the size of the Viewport is much smaller or greater than the Window. In these cases, we have to increase or decrease the size of the Window according to the Viewport and for this, we need some mathematical calculations.
(xw, yw): A point on Window (xv, yv): Corresponding point on Viewport
- we have to calcuate the point (xv, yv)
- Now the relative position of the object in Window and Viewport are same.
For x coordinate,
For y coordinate,
- so, after calculating for x and y coordinate, we get
- where, sx is scaling factor of x coordinate and sy is scaling factor of y coordinate
- for window, Xwmin = 20, Xwmax = 80, Ywmin = 40, Ywmax = 80.
- for viewport, Xvmin = 30, Xvmax = 60, Yvmin = 40, Yvmax = 60.
- Now a point ( Xw, Yw ) be ( 30, 80 ) on the window. We have to calculate that point on viewport
i.e ( Xv, Yv ).
- First of all, calculate scaling factor of x coordinate Sx and scaling factor of y coordinate Sy using above mentioned formula.
Sx = ( 60 - 30 ) / ( 80 - 20 ) = 30 / 60 Sy = ( 60 - 40 ) / ( 80 - 40 ) = 20 / 40
- So, now calculate the point on viewport ( Xv, Yv ).
Xv = 30 + ( 30 - 20 ) * ( 30 / 60 ) = 35 Yv = 40 + ( 80 - 40 ) * ( 20 / 40 ) = 60
- So, the point on window ( Xw, Yw ) = ( 30, 80 ) will be ( Xv, Yv ) = ( 35, 60 ) on viewport.
Here is the implementation of the above approach:
The point on viewport: (35, 60 )
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