Page 103 - DCAP504_Computer Graphics

Computer Graphics

The scale factors (Sx, Sy) are:
xv max − xv min
S =
x
xw max − xw min

yv max − yv min
S y =
yw max − yw min
The translation factors (Tx, Ty) are:

xw max xv min − xw min xv max
t =
x
xw max − xw min

yw max yv min − yw min yv max
t y = yw max − yw min

In the interface window, the position of the viewport can be changed by allowing objects to be viewed
at different positions. Multiple viewports can also be used to display different sections of a scene at
different screen positions. To manipulate the size and proportion of the object, the dimensions of the
viewport must be changed. By mapping different dimensioned clipping windows on a fixed sized
viewport, a zooming effect is being given to the object. The image will have a vague look if the aspect
ratio of the world window and the viewport are different.
Tiling Using the Window-to-Viewport Transformation
Tiling is defined as the number of copies drawn of the same image in rows and columns across the
interface window so that they cover the entire window. A picture that has been copied several times is
called a motif. In computer graphics, tiling is acquired by keeping the window static and changing the
viewport several times. The picture is redrawn every time the viewport is changed.

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