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Window
Window is that portion of the geometric model or object in MCS which is selected for viewing or
Display. It is an area enclosed by a boundary.
Viewport
Viewport. Is an area on a screen, in UCS, where the contents of the window are displayed?
The mapping or transformation of a geometric model from the window (Model Coordinate System) to the viewport (User Coordinate System) is called as viewing transformation or window-to-viewport transformation.
Cohen-Sutherland line clipping algorithm is the oldest and most popular method used for the line clipping. The CohenโSutherland algorithm is a computer-graphics algorithm used for line clipping. The algorithm divides a two-dimensional space into 9 regions and then efficiently determines the lines and portions of lines that are visible in the central region of interest (the viewport).
Object-Space Methods:
An object space method compares the objects and entities of objects to each other within the
scene to determine which are hidden and which visible entities of the objects are.
Most of the hidden-line removal algorithms use object-space method
Algorithms used for hidden-line removal :
I. Floating horizon algorithm
II. Image space algorithm
III. List priority algorithm
IV. Object space algorithm
V. Apple algorithm
VI. Roberts algorithm
VII. Warnock algorithm
Image space Method:
In an image-space method, visibility is decided point by point at each pixel position on the
projection plane.
Most of the hidden-surface removal algorithms use image-space method.
Algorithms used for hidden-surface removal :
I. z-buffer algorithm
II. Scan line Z-buffer algorithm
III. A-buffer algorithm
IV. Object space algorithm
V. List priority algorithm
VI. Roberts algorithm
VII. Warnock algorithm
Definition of non-parametric representation :
In non-parametric or generic representation, the curve is represented as a relationship between
x, y and z.
Definition of parametric representation:
In parametric representation, the curve is represented not as the relationship between x, y and z
but as a function of independent parameter "u'. The independent parameter 'u' acts as a local
coordinate for the points on the curve.
Synthetic curves :
The curves which are defined by the set of data points are known as synthetic curves. As the
synthetic curves are constructed to pass through a given data points, they are of polynomial
form.
Types of Synthetic Curves
I. Cubic Splines
II. Bezier Curves
III. B-Spline Curves
In wire frame modeling, a geometric model of an object is created by using two dimensional geometric entities such as Points, lines, curves, Polygons, etc. Wire-frame models contain only geometric data.
In solid modeling, a geometric model of on object is created by using three dimensional geometric entities,known as, primitives. Solid model contains both geometric data topological information.
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