1. What are the various representation schemes used in three dimensional objects?
- Boundary representation (B-res) – describe the 3 dimensional object as a set of surfaces that separate the object interior from the environment.
- Space-portioning representation – describe interior properties, by partitioning the spatial region containing an object into a set of small, no overlapping, contiguous solids.
2. What is Polygon mesh?
Polygon mesh is a method to represent the polygon, when the object surfaces are tiled, it is more convenient to specify the surface facets with a mesh function. The various meshes are Triangle strip – (n-2) connected triangles Quadrilateral mesh – generates (n-1)(m-1) Quadrilateral
3. What is Bezier Basis Function?
Bezier Basis functions are a set of polynomials, which can be used instead of the primitive polynomial basis, and have some useful properties for interactive curve design.
4. What is surface patch?
A single surface element can be defined as the surface traced out as two parameters (u, v) take all possible values between 0 and 1 in a two-parameter representation. Such a single surface element is known as a surface patch.
5. Write short notes on rendering bi-cubic surface patches of constant u and v method?
The simple way is to draw the iso-parmetric lines of the surface. Discrete
approximations to curves on the surface are produced by holding one parameter constant
and allowing the other to vary at discrete intervals over its whole range. This produce
curves of constant u and constant v.
6. What are the advantages of rendering polygons by scan line method?
i. The max and min values of the scan were easily found.
ii. The intersection of scan lines with edges is easily calculated by a simple incremental method.
iii. The depth of the polygon at each pixel is easily calculated by an incremental method.
7. What are the advantages of rendering by patch splitting?
i. It is fast-especially on workstations with a hardware polygon-rendering pipeline.
ii. It’s speed can be varied by altering the depth of sub-division.
8. Define B-Spline curve?
A B-Spline curve is a set of piecewise(usually cubic) polynomial segments that pass close to a set of control points. However the curve does not pass through these control points, it only passes close to them.
9. What is a spline?
To produce a smooth curve through a designed set of points, a flexible strip called spline is used. Such a spline curve can be mathematically described with a piecewise cubic polynomial function whose first and second derivatives are continuous across various curve section.
10. What is the use of control points?
Spline curve can be specified by giving a set of coordinate positions called control points, which indicates the general shape of the curve, can specify spline curve.
11. What are the different ways of specifying spline curve?
• Using a set of boundary conditions that are imposed on the spline.
• Using the state matrix that characteristics the spline
• Using a set of blending functions that calculate the positions along the curve path by specifying combination of geometric constraints on the curve
12. What are the important properties of Bezier Curve?
• It needs only four control points
• It always passes through the first and last control points
• The curve lies entirely within the convex half formed by four control points.
No comments:
Post a Comment