computer graphics exam questions and answers latest 2022 Graded A+

computer graphics exam questions and answers latest 2022 Graded A+ what are world coordinate system the main frame in the computer graphics in which all others are related to it The primary frame is the world coordinate system (WCS), also known as the universe or global or sometimes model coordinate system. This is the base reference system for the overall model (generally in 3D), to which all other model coordinates relate. what are the object coordinate system When each object is created in a modelling program, a point must be picked to be the origin of that particular object, and the orientation of the object to a set of model axes the most related coordinate system to word coordinate system define viewing transformation and projection transformation The viewing transformation is the operation that maps a perspective view of an object in world coordinates into a physical device's display space Projection. Projection in computer graphics means the transformation of a three-dimensional (3D) area into a two-dimensional (2D) area. The plane in the area into which we transform (project) objects is called the 'Table'. projection transformation have two main types which are parallel projection perspectve projection which type of projection are suitable for the following scale architectural diagram we use the parallel projection but in realistic rendering of indoor scene we use the perspective projection what method used in clipping in computer graphics cohenen surtherland method are used what does cohonen sutherland method depend on? inside outside window code inwhich the code that not have the 0000 will be not accpeted and which have the 0000 will be accepted coheone sutherland main points 1-'inside-outside window codes'. To determine whether endpoints are inside or outside a window 2-As you proceed around the window, nine regions are created - the eight outside regions and the one inside region 3-. Each of the nine regions associated with the window is assigned a 4-bit code to identify the region 4-Each bit in the code is set to either a 1(true) or a 0(false): rules in the Cohen-Sutherland line-clipping algorithm First bit set 1: point lies to the left of the window, x xmin Second bit set 1: point lies to the right of the window, x xmax Third bit set 1: point lies below (bottom) of the window, y ymin Fourth bit set 1: point lies above (top) of the window, y ymax cohen sutherland and logical or The logical OR of the endpoint codes determines if the line is completely inside the window. If the logical OR is zero, the line can be trivially accepted. For example, if the endpoint codes are 0000 and 0000, the logical OR is 0000 - the line can be trivially accepted. If the endpoint codes are 0000 and 0110, the logical OR is 0110 and the line cannot be trivially accepted. what are the underlying concept of painter algorithm for hidden surface ? It relies on the observation that if you paint on a surface, you paint over anything that had previously been there, thus hiding it; namely, paint from furthest to nearest polygons. sort the list of polygons by distance from viewpoint (furthest away at start of list) repeat the following for all polygons in the ordered list: draw projected polygon what are the situation which is not easily handled by the painters algorithm not so good for more complex surface topologies such as certain overlapping polygons or the presence of holes). types of filling in computer graphics recursive filling ordered filling scaline filling what are the difference between the recurise filling and the scaline filling A pixel lying within the region to be filled is taken as a seed and set to record the chosen colour. The seed's nearest neighbours are found and, with each in turn, this procedure is carried out recursively. The process continues until the boundary is reached. The polygon is filled by stroking across each row and colouring any pixels on that row if they lie within the polygon: what are the shader variable uniform have a single value passed per object or render. They are set by the CPU program and do not change until the CPU program starts a new shader. They can be read in any shader but not written to. Examples include light positions and transform matrices. attribute variable in shader programmin attribute: These variables have a different value for each vertex. These are sent from the CPU to the shader as part of the vertex data (typically in an array). They can be read in a vertex shader but not written to. Examples include vertex position and normal varying variable in shader programming varying: are values that are passed from the vertex shader to the fragment shader. The vertex shader computes their values for each vertex and the rasteriser interpolates them to get a value for each fragment, which is passed to the fragment shader. They can be written to in the vertex shader and read in the fragment shader local variable in shader programming local: these behave like standard local variables in a CPU program. They can both be written to and read from in a shader, but only exist within the scope of a single run of a single shader. texture mapping vs procedural mapping texture mapping in which use ppicture image to make texture over 3d object but have an issue is that the resoultion will decrease as the image size increase or zoomed but procedural textureing in which we create the image and it helpful that image not affected by size increase Rather than storing a value for each coordinate, 3D texture functions use a mathematical procedure to compute a value based on the coordinate, hence the name 'procedural textures'. procedural texuring create the texture itself scaled larger without lose resolution explain the process in which we use cylinderical in texture mapping Some surfaces are more difficult to texture map, like the problems encountered when giftwrapping a cylinder or a spherical object. In this case, an (x, y, z) value is converted to cylindrical coordinates (radius, theta, height). The radius is not used. To find the required colour in the 2D texture map, theta is converted into an x-coordinate and height is converted into a y-coordinate, meaning the texture map is wrapped around the object describe threee coordinate system which are used in texture mapping world coordinate object coordinate map entity The map entity determines what we use as the (x, y, z) value. It could be a point on the object, the surface normal, a vector running from the object's centroid through the point, or perhaps the reflection vector at the current point why global illumination is required to get super photorealism ? A global illumination model adds to the local model the light that is reflected from other surfaces to the current surface. A global illumination model is more comprehensive, more physically correct, and produces more realistic images. It is also a great deal more computationally expensive what are six element of computer graphics system 1. Input devices 2. Central processing unit (CPU) 3. Graphics processing unit (GPU) 4. Memory 5. Framebuffer 6. Output devices. what are the stages of pipeline ? model transformation projections rasterization display picture element pixel in which form the image are represented in graphics ? displayed as array of two dimensional pixels how does we represent coordinates of pixel? coordinates of (x,y) indicate row and column what does the rasterization process do? take 3 d scene and rasterise it to 2d discrete primitives what are the idea of rasterization process? t convert the geometry in vectors to images in pixels or dots methods to construct the 3d scene? may create in modelling package or can be created from data capture devices such as leser scanner what are the main component of 3d primitives ? composed of cubes polygons line and primitives what are the most common type the 3 d models are composed from it ? the most common type are triangles or quadrangles wy triangles are most suitble for computer 3 d scene formation? because they tend to be planar in the same model or scene created are called ? wire frame what are the types of coordinate system ? World Object Local Viewpoint(camera) Screen what are the world coordinate system? called universe or global coordinate system it is the main coordinate system in which all coordinates system are referenced to that coordinate system what are object coordinate system? object coordinate system in which he object centre or point related to it examples of object coordinate system car there is a point local coordinate system moving system that can be positioned anywhere in 3-D space by the user to assist in the construction of geometry other name to the view point system viewpoint coordinate system, also known as the camera coordinate system what are the base of view point coordinate system ? This is based upon the viewpoint of the observer, and changes as they change their view. Moving an object 'forward' in this coordinate system moves it along the direction that the viewer happens to be looking at the time. Screen coordinate system