Computer Graphics · Unit 5 · 7 hrs
3D Objects Representation
Exam-focused notes for 3D Objects Representation (Computer Graphics, CSC214): what the TU syllabus asks and how it has actually been tested, with 13 solved past questions from this unit.
What this unit covers
- Representing Surfaces: Boundary and Space partitioning
- Polygon Surface: Polygon tables, Surface normal and Spatial orientation of surfaces, Plane equations, Polygon meshes
- Wireframe Representation
- Blobby Objects
- Representing Curves: Parametric Cubic Curves, Spline Representation, Cubic spline interpolation, Hermite Curves, Bezier and B-spline Curve and surface
- Quadric Surface: Sphere and Ellipsoid
Representing Curves
Construct the Bezier curve with the following polygon vertices (control points): A(1,1), B(2,3), C(4,3), and D(6,4). [5]
Control points (4 points → cubic Bezier, degree $n = 3$): - $P0 = A(1, 1)$ - $P1 = B(2, 3)$ - $P2 = C(4, 3)$ - $P3 = D(6, 4)$ $$P(u) = \sum{k=0}^{3} Pk \, BEZ{k,3}(u), \quad 0 \le u \le 1$$ $$BEZ{k,3}(u) = \binom{3}{k} u^k (1-u)^{3-k}$$ $k$ Blending Functio...
Full solved answer →Explain about parametric curve. Describe the properties of Bezier curve. [5]
--- A curve is an infinitely large set of points. Curves are broadly classified into three categories: explicit, implicit, and parametric curves. Curves having parametric form are called parametric curves. A two-dimensional parametric curve has the followin...
Full solved answer →Discuss the strength and weakness of the human visual system. Describe Spline representation for the curve. [5]
--- (Standard CS/Graphics knowledge, Do not cover this topic directly.) Strength ------------- 1 Wide dynamic range: The human eye can adapt to a very large range of light intensities, from bright sunlight to dim moonlight. 2 Color perception: The eye can d...
Full solved answer →Define fractal. Explain the Bezier curve and B-Spline curve. [5]
--- A fractal is a geometric figure or natural phenomenon that exhibits self-similarity at every scale of magnification. This means a fractal looks similar (or identical) when zoomed in or out at any level. Fractals are used in computer graphics to model co...
Full solved answer →Mention any two color command in OpenGL. Explain about Hermite curve. [5]
--- OpenGL provides color commands primarily in RGBA mode, where colors are specified using Red, Green, Blue, and optionally Alpha (transparency) components mapped onto the range (0.0, 1.0). This command specifies a color using three floating-point values f...
Full solved answer →Polygon Surface
Explain polygon surface representation using Polygon table and polygon meshes. [5]
The most commonly used boundary representation for a 3D graphics object is a set of surface polygons that enclose the interior of the object. Many graphics systems store all object descriptions as a set of surface polygons because this simplifies and speeds...
Full solved answer →What is polygon table? Explain the use of this method in 3D object representation. [5]
A polygon table is a data structure used to store and organize all the geometric and attribute information about the surface polygons that make up a 3D object. Since the most commonly used boundary representation (B-rep) for a 3D graphics object is a set of...
Full solved answer →What is the task of a polygon table? Why do we have to remove hidden surfaces? Explain with any one methodology. [5]
--- A polygon table is the specification of polygon surfaces using vertex coordinates and other attributes. It organizes the geometric and qualitative data needed to describe a 3D object. Polygon tables are organized into two groups: Three lists are maintai...
Full solved answer →How polygon table is used in representing polygons? Explain the representations of any three curves.[10]
--- The most commonly used boundary representation (B-rep) for a 3D graphics object is a set of surface polygons that enclose the interior of the object. Many graphics systems store all object descriptions as a set of surface polygons because it simplifies ...
Full solved answer →Blobby Objects
What are blobby objects? How it is represented? Explain the wireframe representation of 3D objects. [5]
--- Definition: Objects that do not maintain a fixed shape but change their surface characteristics in certain motions are known as blobby objects. Examples: - Molecular structures - Water droplets - Melting objects - Soft organic shapes (muscles, clouds) T...
Full solved answer →Define blobby objects. Describe about basic illumination models. [5]
--- Blobby objects are objects that do not maintain a fixed shape but change their surface characteristics during certain motions or interactions. Examples: - Molecular structures - Water droplets - Melting objects - Muscle tissue deformation Several models...
Full solved answer →Quadric Surface
What is quadric surface? Compare between diffuse reflection and specular reflection. [5]
--- A quadric surface is a frequently used class of 3D objects described by second-degree (quadratic) equations. These surfaces are defined mathematically using polynomials of degree two in x, y, and z. Common examples of quadric surfaces include: - Spheres...
Full solved answer →Wireframe Representation
What is the purpose of wireframe representation? Describe about boundary and space partitioning. [5]
A wireframe model represents a 3D object by describing only its edges and vertices (corners). It is the simplest form of 3D object representation. Purposes: - To provide a quick and simple visual outline of a 3D object using only its edges and corner points...
Full solved answer →Make Unit 5 stick
Practice CSC214 with flashcards & quizzes