tailieunhanh - Lecture Computer graphics: Lecture 32 - Fasih ur Rehman

This chapter defines system software and discusses two types of system software: operating systems and utility programs. You learn what an operating system is and explore user interfaces, operating systems features, and operating system functions. | Computer Graphics Lecture 32 Fasih ur Rehman 3D Transforms The idea of 3D transforms is the same as that of 2D A 3D point is represented by (x, y, z) Homogeneous Coordinates are defined as A 4th Coordinate is added to every 3D point (x, y, z, t) represents (x/t, y/t, z/t) (x, y, z, 0) represents infinity (0, 0, 0, 0) is not allowed General 3D Homogeneous Transform Scaling Scaling matrix Translation Translation matrix Reflection Reflection Matrix about yz – plane What are other reflection matrices Rotation Rotation about Z – axis Rotation Rotation about Y – axis Rotation Rotation about X – axis Inverse Rotation Implementation Tasks Four Major Tasks Modeling Geometry Processing Rasterization Frame Processing Modeling The usual results of the modeling process are sets of vertices that specify a group of geometric objects supported by the rest of the system. Geometry Processing Geometry processing means to determine which geometric objects can appear on the display and to assign shades or | Computer Graphics Lecture 32 Fasih ur Rehman 3D Transforms The idea of 3D transforms is the same as that of 2D A 3D point is represented by (x, y, z) Homogeneous Coordinates are defined as A 4th Coordinate is added to every 3D point (x, y, z, t) represents (x/t, y/t, z/t) (x, y, z, 0) represents infinity (0, 0, 0, 0) is not allowed General 3D Homogeneous Transform Scaling Scaling matrix Translation Translation matrix Reflection Reflection Matrix about yz – plane What are other reflection matrices Rotation Rotation about Z – axis Rotation Rotation about Y – axis Rotation Rotation about X – axis Inverse Rotation Implementation Tasks Four Major Tasks Modeling Geometry Processing Rasterization Frame Processing Modeling The usual results of the modeling process are sets of vertices that specify a group of geometric objects supported by the rest of the system. Geometry Processing Geometry processing means to determine which geometric objects can appear on the display and to assign shades or colors to the vertices of these objects. Four Tasks Projection Primitive assembly Clipping Shading Hidden surface removal and visible surface determination are required Rasterization Calculation of pixel values based upon the previous steps i. e. Projection, Primitive assembly, Clipping and Shading The rasterizer starts with vertices in normalized device coordinates but outputs fragments whose locations are in units of the display—window coordinates. Viewport transformation Clipping Identification of the portions of geometric primitives by analytical calculations within the view windows Clipping Not to clip means Rasterize outside framebuffer time to convert pixels outside the window will be wasted Clipping Algorithms For each line segment for each edge of the window view find intersection points pick nearest points if anything is left draw it Line Clipping A clipper decides which primitives, or parts of primitives can possibly be displayed and be passed on to rasterizer. Primitives .