display file structure in computer graphics tutorial

The set of polygons or faces, together form the “skin” of the object. In polygon mesh, each edge is shared by at most two polygons. Such surfaces are called polygonal meshes. To obtain the above equations in determinant form, apply Cramer’s rule to the above equations.įor any point (x, y, z) with parameters A, B, C, and D, we can say that −Īx + By + Cz + D ≠ 0 means the point is not on the plane.Īx + By + Cz + D 0 means the point is outside the surface.ģD surfaces and solids can be approximated by a set of polygonal and line elements. Let us solve the following simultaneous equations for ratios A/D, B/D, and C/D. Let us assume that three vertices of the plane are (x 1, y 1, z 1), (x 2, y 2, z 2) and (x 3, y 3, z 3). We can obtain the values of A, B, C, and D by solving a set of three plane equations using the coordinate values for three non collinear points in the plane. Where (x, y, z) is any point on the plane, and the coefficients A, B, C, and D are constants describing the spatial properties of the plane. The equation for plane surface can be expressed as − From the following figure, surface S 1 is covered by edges E 1, E 2 and E 3 which can be represented in the polygon surface table as S 1: E 1, E 2, and E 3. Polygon surface table stores the number of surfaces present in the polygon. In the following figure, edge E 1 lies between vertex v 1 and v 2 which is represented in the table as E 1: v 1, v 2. The Edge table is used to store the edge information of polygon. As shown in the following figure, there are five vertices, from v 1 to v 5.Įach vertex stores x, y, and z coordinate information which is represented in the table as v 1: x 1, y 1, z 1. In this method, the surface is specified by the set of vertex coordinates and associated attributes. Then realistic scenes are produced by interpolating shading patterns across polygon surface to illuminate.

The polygon surfaces are common in design and solid-modeling applications, since their wireframe display can be done quickly to give general indication of surface structure. This simplifies and speeds up the surface rendering and display of object since all surfaces can be described with linear equations. Set of polygons are stored for object description. The most commonly used boundary representation for a 3D graphics object is a set of surface polygons that enclose the object interior. Space–partitioning representations − It is used to describe interior properties, by partitioning the spatial region containing an object into a set of small, non-overlapping, contiguous solids (usually cubes). 3D object representation is divided into two categories.īoundary Representations (B-reps) − It describes a 3D object as a set of surfaces that separates the object interior from the environment.

Objects are represented as a collection of surfaces.

Display file structure in computer graphics tutorial