# PDF FOR COMPUTER GRAPHICS

Introduction to Computer Graphics. Version , January David J. Eck. Hobart and William Smith Colleges. This is a PDF version of a free on-line book that. Computer Graphics i. About the Tutorial. To display a picture of any size on a computer screen is a difficult process. Computer graphics are used to simplify this . Torsten Möller. Introduction to. Computer Graphics. Torsten Möller. TASC [email protected] ppti.info~torsten.

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Welcome to CM — Fundamentals of Computer Graphics. All Computer Graphics demands a working knowledge of linear algebra (matrix manipula-. fabio pellacini • 6 problems in graphics. • 3D rendering. – visibility estimation. – lighting simulation. – materials simulation. [Cornell PCG]. [Cornell PCG]. Graphics. 2. Computer-Aided Design. Presentation Graphics. 'I Computer Art l 3 Entertainment. Education and Training. 2 1. Visualization.

Typical of the early move to high-resolution computer graphics intelligent workstations for the computer-aided engineering market were the Orca , and workstations, developed by Orcatech of Ottawa, a spin-off from Bell-Northern Research , and led by David Pearson , an early workstation pioneer. It was targeted squarely at the sophisticated end of the design engineering sector. Artists and graphic designers began to see the personal computer, particularly the Commodore Amiga and Macintosh , as a serious design tool, one that could save time and draw more accurately than other methods.

The Macintosh remains a highly popular tool for computer graphics among graphic design studios and businesses. Modern computers, dating from the s, often use graphical user interfaces GUI to present data and information with symbols, icons and pictures, rather than text.

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Graphics are one of the five key elements of multimedia technology. According to the Information Processing Society of Japan: "The core of 3D image rendering is calculating the luminance of each pixel making up a rendered surface from the given viewpoint, light source , and object position. The LINKS-1 system was developed to realize an image rendering methodology in which each pixel could be parallel processed independently using ray tracing. By developing a new software methodology specifically for high-speed image rendering, LINKS-1 was able to rapidly render highly realistic images.

It was used to create the world's first 3D planetarium -like video of the entire heavens that was made completely with computer graphics. The video was presented at the Fujitsu pavilion at the International Exposition in Tsukuba. Important advances in chroma keying "bluescreening", etc. Two other pieces of video would also outlast the era as historically relevant: Dire Straits ' iconic, near-fully-CGI video for their song " Money for Nothing " in , which popularized CGI among music fans of that era, and a scene from Young Sherlock Holmes the same year featuring the first fully CGI character in a feature movie an animated stained-glass knight.

In the late s, SGI computers were used to create some of the first fully computer-generated short films at Pixar , and Silicon Graphics machines were considered a high-water mark for the field during the decade. The s is also called the golden era of videogames ; millions-selling systems from Atari , Nintendo and Sega , among other companies, exposed computer graphics for the first time to a new, young, and impressionable audience - as did MS-DOS -based personal computers, Apple IIs and Macs , and Amigas , which also allowed users to program their own games if skilled enough.

In the arcades , advances were made in commercial, real-time 3D graphics. In , the first dedicated real-time 3D graphics boards were introduced in arcades, with the Namco System 21 [10] and Taito Air System.

Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. Home computers became able to take on rendering tasks that previously had been limited to workstations costing thousands of dollars; as 3D modelers became available for home systems, the popularity of Silicon Graphics workstations declined and powerful Microsoft Windows and Apple Macintosh machines running Autodesk products like 3D Studio or other home rendering software ascended in importance.

By the end of the decade, the GPU would begin its rise to the prominence it still enjoys today. The field began to see the first rendered graphics that could truly pass as photorealistic to the untrained eye though they could not yet do so with a trained CGI artist and 3D graphics became far more popular in gaming , multimedia , and animation. In film, Pixar began its serious commercial rise in this era under Edwin Catmull , with its first major film release, in - Toy Story - a critical and commercial success of nine-figure magnitude.

The studio to invent the programmable shader would go on to have many animated hits, and its work on prerendered video animation is still considered an industry leader and research trail breaker. In video games, in , Virtua Racing , running on the Sega Model 1 arcade system board , laid the foundations for fully 3D racing games and popularized real-time 3D polygonal graphics among a wider audience in the video game industry.

Back on the PC, Wolfenstein 3D , Doom and Quake , three of the first massively popular 3D first-person shooter games, were released by id Software to critical and popular acclaim during this decade using a rendering engine innovated[ vague ] primarily by John Carmack. The Sony Playstation , Sega Saturn , and Nintendo 64 , among other consoles, sold in the millions and popularized 3D graphics for home gamers. Technology and algorithms for rendering continued to improve greatly.

In , Krishnamurty and Levoy invented normal mapping - an improvement on Jim Blinn's bump mapping. By the end of the decade, computers adopted common frameworks for graphics processing such as DirectX and OpenGL. Since then, computer graphics have only become more detailed and realistic, due to more powerful graphics hardware and 3D modeling software. AMD also became a leading developer of graphics boards in this decade, creating a "duopoly" in the field which exists this day.

CGI became ubiquitous in earnest during this era. Video games and CGI cinema had spread the reach of computer graphics to the mainstream by the late s and continued to do so at an accelerated pace in the s.

CGI was also adopted en masse for television advertisements widely in the late s and s, and so became familiar to a massive audience. The continued rise and increasing sophistication of the graphics processing unit were crucial to this decade, and 3D rendering capabilities became a standard feature as 3D-graphics GPUs became considered a necessity for desktop computer makers to offer.

The Nvidia GeForce line of graphics cards dominated the market in the early decade with occasional significant competing presence from ATI. Shaders which had been introduced in the s to perform specialized processing on the GPU would by the end of the decade become supported on most consumer hardware, speeding up graphics considerably and allowing for greatly improved texture and shading in computer graphics via the widespread adoption of normal mapping , bump mapping , and a variety of other techniques allowing the simulation of a great amount of detail.

Computer graphics used in films and video games gradually began to be realistic to the point of entering the uncanny valley. CGI movies proliferated, with traditional animated cartoon films like Ice Age and Madagascar as well as numerous Pixar offerings like Finding Nemo dominating the box office in this field. The Final Fantasy: The Spirits Within , released in , was the first fully computer-generated feature film to use photorealistic CGI characters and be fully made with motion capture.

Star Wars also resurfaced with its prequel trilogy and the effects continued to set a bar for CGI in film. Geometry, OpenGL 1. Light and Material, Three. Computer Graphics David M.

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Mount David M. In particular,it will consider methods for modeling 3-dimensional objects and efficiently generating photorealistic renderings on color raster graphics devices. Introduction to Computer Graphics I Dr. John T. Graphics Programming Black Book M. Much of the focus of this book is on profiling and code testing, as well as performance optimization. It also explores much of the technology behind the Doom and Quake 3-D games, and 3-D graphics problems such as texture mapping, hidden surface removal, and the like.

Thanks to Michael for making this book available. Badler Norman I. Badler, Cary B.

## Computer graphics

Phillips and Bonnie L. Webber PDF Pages English This book is intended for human factors engineers requiring current knowledge of how a computer graphics surrogate human can augment their analyses of designed environments.

It will also help inform design engineers of the state-of-the-art in human gure modeling, and hence of the human-centered design central to the emergent notion of Concurrent Engineering. Fill all those pair of coordinates that are inside polygons and ignore the alternate pairs. Flood Fill Algorithm Sometimes we come across an object where we want to fill the area and its boundary with different colors.

We can paint such objects with a specified interior color instead of searching for particular boundary color as in boundary filling algorithm. Instead of relying on the boundary of the object, it relies on the fill color.

In other words, it replaces the interior color of the object with the fill color. When no more pixels of the original interior color exist, the algorithm is completed.

Once again, this algorithm relies on the Four-connect or Eight-connect method of filling in the pixels. But instead of looking for the boundary color, it is looking for all adjacent pixels that are a part of the interior. This algorithm picks a point inside an object and starts to fill until it hits the boundary of the object.

The color of the boundary and the color that we fill should be different for this algorithm to work. In this algorithm, we assume that color of the boundary is same for the entire object. The boundary fill algorithm can be implemented by 4-connetected pixels or 8- connected pixels.

We are putting the pixels above, below, to the right, and to the left side of the current pixels and this process will continue until we find a boundary with different color. Initialize the value of seed point seedx, seedy , fcolor and dcol. Define the boundary values of the polygon. Check if the current seed point is of default color, then repeat the steps 4 and 5 till the boundary pixels reached.

Change the default color with the fill color at the seed point. Recursively follow the procedure with four neighborhood points.

Exit There is a problem with this technique. Consider the case as shown below where we tried to fill the entire region. Here, the image is filled only partially. In such cases, 4- connected pixels technique cannot be used. We are putting pixels above, below, right and left side of the current pixels as we were doing in 4- connected technique.

In addition to this, we are also putting pixels in diagonals so that entire area of the current pixel is covered. This process will continue until we find a boundary with different color. Recursively follow the procedure with four neighbourhood points.

Inside-outside Test This method is also known as counting number method.

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While filling an object, we often need to identify whether particular point is inside the object or outside it. There are two methods by which we can identify whether particular point is inside an object or outside.

If the number of interactions is odd, then the point x,y is an interior point; and if the number of interactions is even, then the point x,y is an exterior point.

The following example depicts this concept. From both ends, the number of interaction points is odd, so the point is considered within the object. Nonzero Winding Number Rule This method is also used with the simple polygons to test the given point is interior or not. It can be simply understood with the help of a pin and a rubber band. Fix up the pin on one of the edge of the polygon and tie-up the rubber band in it and then stretch the rubber band along the edges of the polygon.

When all the edges of the polygon are covered by the rubber band, check out the pin which has been fixed up at the point to be test. If we find at least one wind at the point consider it within the polygon, else we can say that the point is not inside the polygon. In another alternative method, give directions to all the edges of the polygon. Draw a scan line from the point to be test towards the left most of X direction. So the point is said to be an interior point.

The viewing transformation is insensitive to the position of points relative to the viewing volume — especially those points behind the viewer — and it is necessary to remove these points before generating the view.

Point Clipping Clipping a point from a given window is very easy. Consider the following figure, where the rectangle indicates the window.

Point clipping tells us whether the given point X, Y is within the given window or not; and decides whether we will use the minimum and maximum coordinates of the window.

Line Clipping The concept of line clipping is same as point clipping. In line clipping, we will cut the portion of line which is outside of window and keep only the portion that is inside the window. We will use 4-bits to divide the entire region. These 4 bits represent the Top, Bottom, Right, and Left of the region as shown in the following figure.

Line can be completely inside the window This line will be completely removed from the region. Line can be completely outside of the window This line will be completely removed from the region.

Line can be partially inside the window We will find intersection point and draw only that portion of line that is inside region. Assign a region code for each endpoints. If both endpoints have a region code then accept this line. Else, perform the logical AND operation for both region codes. Step 3. If the result is not , then reject the line. Else you need clipping. Choose an endpoint of the line that is outside the window. Find the intersection point at the window boundary base on region code.

Replace endpoint with the intersection point and update the region code. Repeat step 2 until we find a clipped line either trivially accepted or trivially rejected. Repeat step 1 for other lines. It employs parametric line representation and simple dot products.

Parametric equation of line is: Sutherland Hodgeman polygon clipping algorithm is used for polygon clipping.

In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window. First the polygon is clipped against the left edge of the polygon window to get new vertices of the polygon.

These new vertices are used to clip the polygon against right edge, top edge, bottom edge, of the clipping window as shown in the following figure. Polygon before Filling While processing an edge of a polygon with clipping window, an intersection point is found if edge is not completely inside clipping window and the a partial edge from the intersection point to the outside edge is clipped.

The following figures show left, right, top and bottom edge clippings: Clipping Left Edge Figure: Clipping Right Edge Figure: Clipping Top Edge Figure: Clipping Bottom Edge Text Clipping Various techniques are used to provide text clipping in a computer graphics. It depends on the methods used to generate characters and the requirements of a particular application. There are three methods for text clipping which are listed below: All or none string clipping 2.

All or none character clipping 3. In all or none string clipping method, either we keep the entire string or we reject entire string based on the clipping window. The following figure shows all or none character clipping: This clipping method is based on characters rather than entire string. In this method if the string is entirely inside the clipping window, then we keep it.

If it is partially outside the window, then: This clipping method is based on characters rather than the entire string.

Bitmap Graphics A bitmap is a collection of pixels that describes an image. It is a type of computer graphics that the computer uses to store and display pictures. In this type of graphics, images are stored bit by bit and hence it is named Bit-map graphics. For better understanding let us consider the following example where we draw a smiley face using bit-map graphics. Bitmap storage of smiley face By observing the original smiley face closely, we can see that there are two blue lines which are represented as B1, B2 and E1, E2 in the above figure.

The main disadvantages of bitmap graphics are: If you try to resize, the pixels get blurred. We can have various types of transformations such as translation, scaling up or down, rotation, shearing, etc. When a transformation takes place on a 2D plane, it is called 2D transformation.

Transformations play an important role in computer graphics to reposition the graphics on the screen and change their size or orientation.

Homogenous Coordinates To perform a sequence of transformation such as translation followed by rotation and scaling, we need to follow a sequential process: Translate the coordinates, 2. Rotate the translated coordinates, and then 3. Scale the rotated coordinates to complete the composite transformation. In this way, we can represent the point by 3 numbers instead of 2 numbers, which is called Homogenous Coordinate system.

In this system, we can represent all the transformation equations in matrix multiplication.

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Translation A translation moves an object to a different position on the screen. The above equations can also be represented using the column vectors.

However, for negative angle rotation, the matrix will change as shown below: In the scaling process, you either expand or compress the dimensions of the object. Scaling can be achieved by multiplying the original coordinates of the object with the scaling factor to get the desired result. This can be mathematically represented as shown below: The above equations can also be represented in matrix form as below: The scaling process is shown in the following figure.

After Scaling Process If we provide values less than 1 to the scaling factor S, then we can reduce the size of the object. If we provide values greater than 1, then we can increase the size of the object. Reflection Reflection is the mirror image of original object. In reflection transformation, the size of the object does not change.

## Computer Graphics Tutorial in PDF

The following figures show reflections with respect to X and Y axes, and about the origin respectively. There are two shear transformations X-Shear and Y-Shear. One shifts X coordinates values and other shifts Y coordinate values. However, in both the cases, only one coordinate changes its coordinates and other preserves its values.

Shearing is also termed as Skewing. X-Shear The X-Shear preserves the Y coordinate and changes are made to X coordinates, which causes the vertical lines to tilt right or left as shown in below figure. The Y-Shear can be represented in matrix from as: Composite transformation can be achieved by concatenation of transformation matrices to obtain a combined transformation matrix. The basic purpose of composing transformations is to gain efficiency by applying a single composed transformation to a point, rather than applying a series of transformation, one after another.

For example, to rotate an object about an arbitrary point Xp, Yp , we have to carry out three steps: Translate point Xp, Yp to the origin. Rotate it about the origin. Finally, translate the center of rotation back where it belonged. It is a continuing area of research in scientific visualization. Furthermore, 3D graphics components are now a part of almost every personal computer and, although traditionally intended for graphics-intensive software such as games, they are increasingly being used by other applications.

Parallel Projection Parallel projection discards z-coordinate and parallel lines from each vertex on the object are extended until they intersect the view plane.

In parallel projection, we specify a direction of projection instead of center of projection. In parallel projection, the distance from the center of projection to project plane is infinite. In this type of projection, we connect the projected vertices by line segments which correspond to connections on the original object.

Parallel projections are less realistic, but they are good for exact measurements. In this type of projections, parallel lines remain parallel and angles are not preserved.

Various types of parallel projections are shown in the following hierarchy. Types of Parallel Projection Orthographic Projection In orthographic projection the direction of projection is normal to the projection of the plane. There are three types of orthographic projections: In oblique projection, we can view the object better than orthographic projection. There are two types of oblique projections: Cavalier and Cabinet. The projection of a line perpendicular to the view plane has the same length as the line itself in Cavalier projection.

In a cavalier projection, the foreshortening factors for all three principal directions are equal. The Cabinet projection makes Both the projections are shown in the following figure: The most common axonometric projection is an isometric projection where the projection plane intersects each coordinate axis in the model coordinate system at an equal distance. In this projection parallelism of lines are preserved but angles are not preserved.

The following figure shows isometric projection: Isometric Projection Perspective Projection In perspective projection, the distance from the center of projection to project plane is finite and the size of the object varies inversely with distance which looks more realistic. The distance and angles are not preserved and parallel lines do not remain parallel.The field of computer graphics developed with the emergence of computer graphics hardware.

Once again, this algorithm relies on the Four-connect or Eight-connect method of filling in the pixels. Each point has two neighbors except endpoints. CGI became ubiquitous in earnest during this era. Two other pieces of video would also outlast the era as historically relevant: Dire Straits ' iconic, near-fully-CGI video for their song " Money for Nothing " in , which popularized CGI among music fans of that era, and a scene from Young Sherlock Holmes the same year featuring the first fully CGI character in a feature movie an animated stained-glass knight.

Thus, in general, we can label any polygon as a back face if its normal vector has a z component value: