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Computer Graphics Viva Question & Answers semester 3

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Module: Introduction and Overview of Graphics System

No. Content
Q1 What is computer graphics?
A1 Computer graphics is the field of study that deals with the generation, manipulation, and representation of visual data using computers. It involves creating, displaying, and interacting with images and animations.
Q2 What are the representative uses of computer graphics?
A2 Computer graphics find applications in various fields, such as entertainment (video games, movies), design (architectural visualization, industrial design), simulations (virtual reality, flight simulators), scientific visualization, and computer-aided design (CAD).
Q3 What is the coordinate system used in computer graphics?
A3 The coordinate system used in computer graphics is typically a Cartesian coordinate system, where a point is represented by its X, Y, and sometimes Z coordinates. The origin (0,0) is usually at the top-left corner of the screen or viewport.
Q4 What is scan conversion in computer graphics?
A4 Scan conversion is the process of converting geometric primitives (points, lines, curves) into their pixel representations on a raster display. It involves determining which pixels to turn on or off to accurately represent the shape being drawn.
Q5 What is rasterization in computer graphics?
A5 Rasterization is the process of generating a raster image from a geometric description. It involves converting vector graphics primitives into a grid of pixels that can be displayed on a raster output device, such as a monitor or printer.
Q6 What is rendering in computer graphics?
A6 Rendering is the process of creating the final 2D image or animation from a 3D scene. It involves determining the colors, shading, and other visual attributes of objects in the scene, considering lighting, materials, and camera settings, to produce a realistic or stylized output.

Module: Output Primitives

No. Content
Q1 Explain the DDA algorithm for line drawing.
A1 The Digital Differential Analyzer (DDA) algorithm is a method for approximating the coordinates of a line between two given points. It calculates the incremental values of x and y based on the slope of the line and then plots the corresponding pixels. It is a simple and efficient line-drawing algorithm.
Q2 How does the Bresenham algorithm for line drawing work?
A2 The Bresenham algorithm is an efficient method for drawing lines on a raster display. It uses integer arithmetic and incremental calculations to determine the pixels to be turned on for a given line. The algorithm avoids floating-point calculations and rounding errors, making it faster than DDA for line drawing.
Q3 What is aliasing in computer graphics?
A3 Aliasing refers to the distortion or jaggedness that can occur in computer-generated images when representing continuous curves or diagonal lines with discrete pixels. It happens because of the mismatch between the resolution of the display and the frequency of the signal being represented.
Q4 What are antialiasing techniques in computer graphics?
A4 Antialiasing techniques are methods used to reduce or eliminate aliasing artifacts in computer graphics. Some techniques include pre-filtering (smoothing the input data before scan conversion), post-filtering (smoothing the output image), super-sampling (sampling at a higher resolution and averaging), and pixel phasing (adjusting pixel intensities based on their positions).
Q5 Explain the scan line polygon fill algorithm.
A5 The scan line polygon fill algorithm is a method for filling a polygon with a specified color. It works by scanning each horizontal line within the polygon’s bounding box and determining which segments of the polygon intersect with that line. The algorithm then fills the pixels between the intersecting segments on the scan line.
Q6 What are the inside-outside tests in polygon filling?
A6 Inside-outside tests are used to determine whether a point lies inside or outside a polygon. One commonly used test is the “even-odd rule,” where a ray is cast from the point and the number of intersections with the polygon’s edges is counted. An odd number of intersections indicates that the point is inside the polygon.

Module: Two Dimensional Geometric Transformations

No. Content
Q1 What are the basic transformations in 2D computer graphics?
A1 The basic transformations in 2D computer graphics are translation, scaling, and rotation.
Q2 How is translation performed in 2D graphics?
A2 Translation in 2D graphics involves shifting an object’s position by adding or subtracting values from its coordinates. It moves the object horizontally and vertically.
Q3 What is scaling in 2D computer graphics?
A3 Scaling is the process of resizing an object by multiplying its coordinates by scaling factors. It can make an object larger (by scaling factors > 1) or smaller (by scaling factors < 1) in size.
Q4 Explain the concept of rotation in 2D graphics.
A4 Rotation in 2D graphics involves rotating an object around a specified point or origin. It can be done by using rotation matrices or trigonometric functions to calculate new coordinates based on an angle of rotation.
Q5 What is the matrix representation of transformations in 2D graphics?
A5 Transformations in 2D graphics can be represented using matrices. Translation, scaling, and rotation matrices can be multiplied together to form composite transformations.
Q6 How do homogeneous coordinates work in 2D graphics?
A6 Homogeneous coordinates are used to represent points in 2D graphics. They extend the Cartesian coordinate system by adding an extra dimension, which simplifies operations like translation and perspective transformations.
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Module: Two-Dimensional Viewing and Clipping

No. Content
Q1 What is the viewing transformation pipeline in 2D graphics?
A1 The viewing transformation pipeline in 2D graphics involves transforming the coordinates of objects from world coordinates to device coordinates. It includes operations such as scaling, rotation, translation, and mapping to the viewport.
Q2 How is the window to viewport coordinate transformation performed in 2D graphics?
A2 The window to viewport coordinate transformation maps the coordinates of the viewing window (defined in world coordinates) to the physical coordinates of the display or viewport. It involves scaling, translation, and possibly flipping or mirroring the coordinates.
Q3 What are the point clipping algorithms in 2D graphics?
A3 Point clipping algorithms are used to determine whether a point lies within the visible region or viewport. One commonly used algorithm is the Cohen-Sutherland algorithm, which divides the viewport into nine regions based on the relative position of the point and the viewport boundaries.
Q4 Explain the Cohen-Sutherland line clipping algorithm.
A4 The Cohen-Sutherland algorithm is a line clipping algorithm that uses a binary code to determine whether a line segment lies entirely within, partially within, or outside the visible region or viewport. It recursively clips the line against the viewport boundaries until a visible segment is obtained.
Q5 What is the Liang-Barsky line clipping algorithm?
A5 The Liang-Barsky algorithm is another line clipping algorithm that computes the intersection points between a line segment and the viewport boundaries. It uses parameterization and interval comparison to determine if the line segment lies within the visible region.
Q6 What are the polygon clipping algorithms in 2D graphics?
A6 Polygon clipping algorithms are used to determine which parts of a polygon lie within the visible region or viewport. Two commonly used algorithms are the Sutherland-Hodgman algorithm and the Weiler-Atherton algorithm. The Sutherland-Hodgman algorithm clips each edge of the polygon against the viewport, while the Weiler-Atherton algorithm handles concave polygons and supports polygon intersection and union operations.

Module: Three Dimensional Geometric Transformations, Curves, and Fractal Generation

No. Content
Q1 What are the 3D geometric transformations in computer graphics?
A1 The 3D geometric transformations in computer graphics include translation, rotation, scaling, and reflection in three dimensions. They are used to manipulate the position, orientation, and size of 3D objects in a scene.
Q2 How is translation performed in 3D graphics?
A2 Translation in 3D graphics involves shifting an object’s position in three dimensions by adding or subtracting values from its X, Y, and Z coordinates. It moves the object along the X, Y, and Z axes.
Q3 Explain the concept of rotation in 3D graphics.
A3 Rotation in 3D graphics involves rotating an object around a specified axis or point in three-dimensional space. It can be done by using rotation matrices or quaternion representations to calculate new coordinates based on an angle of rotation and an axis of rotation.
Q4 What is scaling in 3D computer graphics?
A4 Scaling in 3D computer graphics is the process of resizing an object in three dimensions. It involves multiplying the X, Y, and Z coordinates of the object’s vertices by scaling factors, which can make the object larger or smaller along each axis.
Q5 What are parallel and perspective projections in 3D graphics?
A5 Parallel and perspective projections are methods used to project a 3D scene onto a 2D display or viewport. Parallel projection maintains parallel lines and equal scaling factors along each axis, while perspective projection simulates the way objects appear smaller as they recede into the distance, creating a sense of depth and realism.
Q6 What are Bezier curves in computer graphics?
A6 Bezier curves are a type of curve used in computer graphics to represent smooth and curved paths. They are defined by a set of control points that influence the shape of the curve. Bezier curves are widely used for shape design, animation, and curve interpolation.

Module: Visible Surface Detection and Animation

No. Content
Q1 What is visible surface detection in computer graphics?
A1 Visible surface detection is the process of determining which surfaces or objects in a 3D scene are visible from a given viewpoint. It involves identifying and rendering only the surfaces that are not occluded by other objects, ensuring that the visible surfaces appear correctly in the final image.
Q2 What are the classification of visible surface detection algorithms?
A2 Visible surface detection algorithms can be classified into various categories, such as the object-space methods (which analyze the scene geometry and visibility relationships), image-space methods (which determine visibility based on the projected image), and hybrid methods (which combine object-space and image-space techniques).
Q3 What is the depth buffer method for visible surface detection?
A3 The depth buffer (or Z-buffer) method is a widely used technique for visible surface detection. It involves assigning a depth value (Z-coordinate) to each pixel and comparing the depth values of the surfaces being rendered. Only the closest visible surface at each pixel is retained, ensuring correct occlusion.
Q4 Explain the area subdivision method for visible surface detection.
A4 The area subdivision method, also known as the scan-line method, divides the image or viewport into small areas or scan lines. It scans each area or line and determines the visible surfaces based on comparisons of depth values or other visibility criteria. This method is particularly useful for complex scenes with overlapping objects.
Q5 What is animation in computer graphics?
A5 Animation in computer graphics involves creating the illusion of motion or change over time. It typically involves displaying a series of images (frames) in rapid succession to create the perception of movement. Animation can be used for storytelling, visual effects, character animation, and interactive experiences.
Q6 What are key framing and motion capture in animation?
A6 Key framing is a traditional animation technique where the animator defines specific poses or key frames at important points in an animation sequence, and the computer interpolates the frames in between to create smooth motion. Motion capture, on the other hand, involves recording the movements of real-life actors or objects and using that data to drive the motion of virtual characters or objects in a computer-generated scene.

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