Polygon surfaces-polygon tables-plane
equations-polygon meshes
Object descriptions are stored as
sets of surface polygons
The surfaces are described with
linear equations
Polygon table
data is placed into the polygon
table for processing
Polygon data table can be
organised into two groups
geometric table
attribute table
Quadric surfaces-sphere-ellipsoid-torus
Described
with second degree eqns.
Ex.
Sphere,ellipsoids,tori,paraboloids,hyperboloids
Sphere
A spherical surface with radius ‘r’
centered on the coordinate origin is defined as a set of points(x,y,z) that
satisfy the equation
x2
+ y2 +
z2 = r2
In parametric form,
x = r
CosΦCosΘ
y = r Cos ΦSinΘ
z = r Sin Φ
Blobby objects-definition and
example
Don’t maintain a fixed shape
Change
surface characteristics in certain motions
Ex. Water droplet, Molecular structures
f(x,y,z) = Σk b ke-ak rk2 - T = 0
r = √x2 + y2 + z2
T
=some threshold
a,b used to adjust the amount of
bloobiness.
Spline-representation-interpolation
it
is a composite curve formed with polynomial pieces satisfying a specified
continuity conditions at the boundary of the pieces
Bezier curves
can
be fitted to any no. of control points
degree of bezier polynomial is determined by
the number of control points and their relative position
Bezier
curve is specified by
Boundary conditions
Characterising matrix
Blending function
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