Computer Graphics Viva Question & Answers semester 3

Module: Introduction and Overview of Graphics System

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Q1What is computer graphics?
A1Computer 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.
Q2What are the representative uses of computer graphics?
A2Computer 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).
Q3What is the coordinate system used in computer graphics?
A3The 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.
Q4What is scan conversion in computer graphics?
A4Scan 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.
Q5What is rasterization in computer graphics?
A5Rasterization 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.
Q6What is rendering in computer graphics?
A6Rendering 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

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Q1Explain the DDA algorithm for line drawing.
A1The 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.
Q2How does the Bresenham algorithm for line drawing work?
A2The 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.
Q3What is aliasing in computer graphics?
A3Aliasing 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.
Q4What are antialiasing techniques in computer graphics?
A4Antialiasing 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).
Q5Explain the scan line polygon fill algorithm.
A5The 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.
Q6What are the inside-outside tests in polygon filling?
A6Inside-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

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Q1What are the basic transformations in 2D computer graphics?
A1The basic transformations in 2D computer graphics are translation, scaling, and rotation.
Q2How is translation performed in 2D graphics?
A2Translation in 2D graphics involves shifting an object’s position by adding or subtracting values from its coordinates. It moves the object horizontally and vertically.
Q3What is scaling in 2D computer graphics?
A3Scaling 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.
Q4Explain the concept of rotation in 2D graphics.
A4Rotation 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.
Q5What is the matrix representation of transformations in 2D graphics?
A5Transformations in 2D graphics can be represented using matrices. Translation, scaling, and rotation matrices can be multiplied together to form composite transformations.
Q6How do homogeneous coordinates work in 2D graphics?
A6Homogeneous 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.

Module: Two-Dimensional Viewing and Clipping

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Q1What is the viewing transformation pipeline in 2D graphics?
A1The 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.
Q2How is the window to viewport coordinate transformation performed in 2D graphics?
A2The 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.
Q3What are the point clipping algorithms in 2D graphics?
A3Point 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.
Q4Explain the Cohen-Sutherland line clipping algorithm.
A4The 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.
Q5What is the Liang-Barsky line clipping algorithm?
A5The 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.
Q6What are the polygon clipping algorithms in 2D graphics?
A6Polygon 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

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Q1What are the 3D geometric transformations in computer graphics?
A1The 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.
Q2How is translation performed in 3D graphics?
A2Translation 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.
Q3Explain the concept of rotation in 3D graphics.
A3Rotation 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.
Q4What is scaling in 3D computer graphics?
A4Scaling 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.
Q5What are parallel and perspective projections in 3D graphics?
A5Parallel 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.
Q6What are Bezier curves in computer graphics?
A6Bezier 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

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Q1What is visible surface detection in computer graphics?
A1Visible 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.
Q2What are the classification of visible surface detection algorithms?
A2Visible 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).
Q3What is the depth buffer method for visible surface detection?
A3The 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.
Q4Explain the area subdivision method for visible surface detection.
A4The 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.
Q5What is animation in computer graphics?
A5Animation 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.
Q6What are key framing and motion capture in animation?
A6Key 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.