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Title of test: computer graphics Description: various questions Author: noob saibot Other tests from this author Creation Date: 31/08/2024 Category: Computers Number of questions: 32

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Which of the following statements is INCORRECT? A) If an affine linear transformation T is applied to a surface, then the normal vector N to a point on the surface is mapped to T N. B) Algorithms for digital image compression are usually more efficient, that is, they achieve greater compression, when the images to be compressed have large areas with the same color. C) Local lighting models of synthetic scenes are unable to reproduce global effects such as shadows. D) Two colors with different saturations can have the same luminosity. E) An affine linear transformation always transforms convex objects into convex objects. Regarding the concept of image segmentation, the following is CORRECT: A) Process that groups parts of an image into homogeneous regions with respect to one or more characteristics (brightness, shades of gray, color, texture). B) Operation that aims to partition an image into a set of regions of the same size. C) Process that aims to identify objects in the image according to a previous description based on one or more characteristics (brightness, shades of gray, color, texture). D) It is the same thing as image edge detection. E) None of the above. In the process of synthesizing the image of a three-dimensional scene, also called the graphics pipeline, several operations are executed in sequence. The objective of these operations is to convert the geometric primitives that describe the objects in the scene at a high level, together with the specification of the synthetic camera, into a collection of pixels on the screen. Select the alternative that presents the correct sequence of these operations. a) Projection/Cutout/Rasterization/Visibility b) Cutout/Projection/Visibility/Rasterization c) Projection/Cutout/Visibility/Rasterization d) Projection/Rasterization/Cutout/Visibility e) Cutout/Projection/Rasterization/Visibility. Consider the following statements. I. The Phong lighting model obtains the colors inside the polygons by interpolating the colors at the vertices. II. The z-buffer technique uses primitive ordering to determine the visible pixels. III. The point (2,1,3,2), expressed in homogeneous coordinates, is equivalent to the point (1.0, 0.5, 1.5) in three-dimensional Cartesian coordinates. IV. One of the main advantages of representing objects as triangular polygonal meshes is the guarantee that all faces are planar. Select the correct alternative. a) Only statements I and II are correct. b) Only statements I and IV are correct. c) Only statements III and IV are correct. d) Only statements I, II and III are correct. e) Only statements II, III and IV are correct. Regarding the traditional process of image synthesis in computer graphics, relate the left column with the right column. (I) Perspective Projection (II) Viewing Volume (III) Gouraud Model (IV) Z-buffer Algorithm (V) Rasterization _________ (A) Responsible for removing hidden lines and surfaces. (B) Defines the visible portion of the scene. (C) Maps coordinates in a three-dimensional space to a two-dimensional space. (D) Performs linear interpolation of colors. (E) Finds the pixel coordinates on the screen. Select the alternative that contains the correct association. a) I-B, II-C, III-E, IV-D, V-A. b) I-B, II-E, III-D, IV-C, V-A. c) I-C, II-B, III-D, IV-A, V-E. d) I-C, II-D, III-B, IV-A, V-E. e) I-E, II-B, III-A, IV-D, V-C. In computer graphics scenes, to increase visual realism, it is common to apply a local lighting model that calculates the colors at the vertices of the triangles from the reflection properties of the object, geometric properties of the object and properties of the light source(s). Regarding local lighting models, consider the following statements. I. The diffuse reflection portion depends on the position of the observer. II. The specular portion can be approximated by the Phong model, which establishes that the specular reflection of a surface is proportional to the cosine of the angle between the direction vector of the observer and the vector that establishes the ideal specular reflection direction. III. The ideal diffuse lighting portion can be approximated by Lambert's law, which establishes that the diffuse reflection of a surface is proportional to the angle between the normal vector to the surface and the direction vector of the light source. IV. The ambient light portion approximates the multiple light reflections from the numerous surfaces present in the scene. Select the correct alternative. a) Only statements I and II are correct. b) Only statements I and III are correct. c) Only statements III and IV are correct. d) Only statements I, II and IV are correct. e) Only statements II, III and IV are correct. Conversion of RGB images to grayscale can be accomplished by averaging the color components. However, this conversion produces a brightness scale in which the perception is not equivalent to the brightness in the color image. The proper way to calculate luminance Y is given by the equation: a b c d e. Suppose a three-dimensional scene composed of only two spheres contained in the viewing volume. One of these spheres is completely covered by the other in relation to the view of the virtual camera that uses parallel projection. Based on the statement and the knowledge on the subject, mark the correct alternative. a) Using the Z-Buffer algorithm, the resulting image, after rasterizing both spheres, is the same, regardless of which sphere is rasterized first. b) In the Phong lighting model, the illumination of one of the spheres depends on the color of the second sphere. c) The Gouraud lighting model describes the shadow coming from one of the spheres on the other. d) Hidden surface removal algorithms are not useful in the situation described, since both spheres are inside the viewing volume. e) The covered sphere can be larger than the visible sphere, as long as one is in front, in relation to the view of the camera, and sufficiently distant from each other. Regarding the anti-aliasing technique known as Multi Sampling Anti-Aliasing (MSAA) and considering the rasterization graphics pipeline, select the correct alternative. a) The technique requires two rasterization steps, one to mark the depth map and another to define the pixel colors. b) The geometric primitives must be rasterized in an orderly manner, starting with the furthest to the closest to the virtual camera. c) The technique is not capable of reducing the aliasing resulting from the colors of the textures mapped onto a triangle mesh. d) One of the characteristics of the technique is to reuse information captured from the scene by a sample in the computation of other samples, for example, lighting. e) The distribution of samples must be regular, for example, it must follow a matrix-shaped distribution. Regarding the transforms used in digital image processing, consider the following statements. I. De Haar has a symmetric and separable kernel. II. Discrete cosine has a symmetric and separable kernel. III. De Walsh has an asymmetric and inseparable kernel. IV. De Slant has an asymmetric and inseparable kernel. Select the correct alternative. a) Only statements I and II are correct. b) Only statements I and IV are correct. c) Only statements III and IV are correct. d) Only statements I, II and III are correct. e) Only statements II, III and IV are correct. Regarding Computer Graphics, consider the following statements. I. Given a triangle mesh that approximates a sphere, the smoothness of the lighting generated by the Gouraud algorithm depends on the resolution of the mesh. II. In parallel projection, the viewing volume is rectangular. III. The Bresenham algorithm is a line rasterization algorithm. IV. The aliasing effect does not occur in the rasterization of two-dimensional triangle meshes. Select the correct alternative. a) Only statements I and II are correct. b) Only statements I and IV are correct. c) Only statements III and IV are correct. d) Only statements I, II and III are correct. e) Only statements II, III and IV are correct. Consider the following image. Based on the image and the concepts used in digital image processing, select the alternative that correctly presents the appropriate filter to eliminate the points located on the right side of the image in a way that preserves the triangle as much as possible. a) Average. b) Median. c) Prewitt. d) Roberts. e) Sobel. Relate the Computer Graphics techniques, in the left column, with their functions, in the right column. (I) Phong. (II) Painter's algorithm. (III) Cohen-Sutherland. (IV) BSP. (V) Bézier. (A) Removal of hidden surfaces. (B) Cropping. (C) Lighting. (D) Spatial subdivision. (E) Curve approximation. Select the alternative that contains the correct association. a) I-A, II-B, III-C, IV-E, V-D. b) I-B, II-D, III-A, IV-C, V-E. c) I-B, II-A, III-E, IV-D, V-C. d) I-C, II-A, III-B, IV-D, V-E. e) I-C, II-D, III-B, IV-E, V-A. Read the following definitions. • Let A be a grayscale image. • Let B be the image resulting from the Histogram Equalization of image A. • Let C be the image resulting from the Histogram Equalization of image B. Based on these definitions and the concepts used in digital image processing, consider the following statements. I. The comparison of the histogram of two images is a measure of similarity that indicates whether the two images are visual impressions of the same scene. II. Image B is the same as image C. III. The histogram of the image is a discrete function that represents the probability of finding a certain color in the image. IV. The histogram of two images, in grayscale, provides information on whether one of the images is lighter or darker or has the same brightness. Select the correct alternative. a) Only statements I and II are correct. b) Only statements I and IV are correct. c) Only statements III and IV are correct. d) Only statements I, II and III are correct. e) Only statements II, III and IV are correct. In Computer Graphics, the mipmap technique aims to reduce computational cost and the aliasing effect during the rasterization of surfaces with texture mapping. This is done based on a pre-processing, per texture, which results in an increase in memory consumption. Indicate the alternative that correctly presents how much this increase is in relation to the original texture a) 0.25% b) 0.33% c) 0.50% d) 0.75% e) 100%. Considering filtering in the spatial domain related to the area of ​​digital image processing, associate the name of the convolution kernel, in the left column, with its respective convolution matrix, in the right column. Select the alternative that contains the correct association. a) I-A, II-C, III-D, IV-B. b) I-C, II-A, III-B, IV-D. c) I-C, II-B, III-D, IV-A. d) I-D, II-A, III-C, IV-B. e) I-D, II-C, III-B, IV-A. Regarding the construction of 3D objects in a structure known in computer graphics as a wireframe, consider the following statements. I. It is necessary to obtain the set of vertices of all points of the object. II. It is necessary to obtain the set of points of each face of the object. III. The calculation of the normal of a face is performed using 3 points of the face and the vector product operation. IV. The calculation of the normal of a face is performed using 3 points of the face and the inner product operation. Select the correct alternative. a) Only statements I and II are correct. b) Only statements I and IV are correct. c) Only statements III and IV are correct. d) Only statements I, II and III are correct. e) Only statements II, III and IV are correct. Simulating the propagation of light in the environment, evaluating its interaction with the objects that compose it and considering the interaction of light with its surfaces, is the objective of the algorithm technique (A) Cohen-Sutherland (B) Bresenham (C) Boundary-Fill (D) Sutherland Hodgman (E) Ray Tracing. In the context of image processing, a digital filter is used for the following purposes: (A) detect, recognize, and track objects. (B) evaluate, determine, and judge whether an image can be used. (C) improve, correct, or replace the image acquisition sensor. (D) correct, smooth, or enhance information in an image. (E) preserve, compress, and save the image. MeshSmooth, Bump Map, Flat Shading are, respectively, types of: (A) Modifier, Texture, Rendering Method. (B) Modifier, Rendering Method, Texture. (C) Texture, Rendering Method, Modifier. (D) Texture, Modifier, Rendering Method. (E) Rendering Method, Texture, Modifier. In the context of image processing, a low-pass filter produces the following results: A) It enhances image details, producing a sharpening effect. B) It enhances the geometric properties of the image using predefined masks. C) It smooths frequencies within a predetermined range of values. D) It smooths the image by attenuating high frequencies, which correspond to abrupt transitions. E) It simultaneously enhances and smooths image components. In the context of image processing, histogram equalization has the main objective of: A) Recognizing the objects present in the image. B) Extracting the edges present in the image. C) Improving the contrast of the image. D) Transforming the color scale of the image. E) Eliminating noise in the image. Select the alternative that correctly describes a characteristic of projection transformations. A) Perspective projection preserves angles and object B) Isometric projections are not parallel. C) In a parallel projection, the projection center is considered to be at a certain distance from the projection plane. D) The size of an object's perspective projection varies directly proportionally to the distance of that object from the projection center. E) A perspective projection can be represented by a 4x4 matrix. Considering geometric transformations in two (2D) and three (3D) dimensions, analyze the following assertions: I. Homogeneous coordinates are necessary to represent the translation transformation in a matrix. II. If a uniform scale transformation and a rotation transformation are performed in 2D, the order of the transformations will change the final result. III. If two rotation transformations are performed in 3D: one of 90 degrees around the X axis, and another of 90 degrees around the Z axis, the final result will not be affected by the order of the transformations. Which are correct? A) Only I. B) Only II. C) Only III. D) Only I and III. E) Only II and III. Regarding the wavelet transform for digital image processing, it is correct to state that: A) It is an algorithm that produces classification of objects in the image. B) It is a technique that allows the processing of the image in multiresolution. C) It is a technique capable of extracting frequencies from the image without their temporal location. D) It is a technique that allows the generation of higher resolution images. E) It is an algorithm capable of understanding granular information in digital images. All of the following are digital processing techniques, EXCEPT: A) Morphological processing. B) Sampling and quantization. C) Segmentation. D) Simulated tempering. E) Thresholding. In the three-dimensional visualization process, the region of the universe that will be cut out and projected onto the projection plane is called: A) Perspective projection. B) Viewing volume. C) Camera reference system. D) Observer. E) Front clipping plane. Considering the transformations between 2D coordinate systems and the clipping process, analyze the following assertions: I. The area of ​​the universe that will be mapped to the screen is called a window, and the area of ​​the screen that will be used in this process is called a viewport. II. If the ratios between the width and height of the window and the width and height of the viewport are not the same, a non-uniform change in scale will occur. III. Line clipping can be done in both the universe and screen coordinate systems. Which are correct? A) Only I. B) Only II. C) Only III. D) Only I and E) I, II and III. Image quantization can be understood as a process of: A) Converting each sample into a discrete observation. B) Equalizing the color distribution. C) Correcting the lighting. D) Discretizing the brightness values. E) Mapping the image channels. The purpose of color histogram equalization in a digital image is to: A) Highlight a specific channel. B) Enhance differences in hue. C) Define edges. D) Eliminate extraneous (strange) information. E) Convert to a new color model. The texture mapping technique based on the application of a disturbance function to the surface normal vector, so that its illumination is affected, is called: A) Procedural texture. B) Solid texture. C) Bump mapping. D) Frame mapping. E) Environment mapping. The steps below are part of the 3D visualization pipeline: 1. Normalization and cropping transformation. 2. Viewing (camera) transformation. 3. Modeling transformation. 4. Viewport transformation. 5. Projection transformation. The correct order in which these steps are performed in the process is: hint.: like in db design, you start by modelling the whole thing......... A) 3 – 2 – 5 – 1 – 4. B) 3 – 5 – 2 – 1 – 4. C) 2 – 1 – 4 – 5 – 3. D) 2 – 3 – 4 – 1 – 5. E) 1 – 3 – 2 – 4 – 5.

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