Splines Kochanek-Bartel được thiết kế đường dẫn hình ảnh động mô hình. Đặc biệt, những thay đổi đột ngột chuyển động của một đối tượng có thể được mô phỏng với các giá trị khác không cho tham số cùng, chúng ta có thể expre5s mẫu số trong Eq. 14-46 | Simpo PDF Merge and Split Unregistered Version - http _Chapter where the view-volume boundaries are established by the window limits xwmin Three-Dimensional Viewing xw ywmin yWjnax and the positions zfront and z k of the front and back planes. Viewport boundaries are set with the coordinate values xumin xVnw yvmin yvmax zv n and zv . The additive translation factors Kx Ky and K2 in the transformation are x min min x y y min y min y X2 zvmin -z rontDz 12-35 Viewport Clipping Lines and polygon surfaces in a scene can be clipped against the viewport boundaries with procedures similar to those used for two dimensions except that objects are now processed against clipping planes instead of clipping edges. Curved surfaces are processed using the defining equations for the surface boundary and locating the intersection lines with the parallelepiped planes. The two-dimensional concept of region codes can be extended tọ three dimensions by considering positions in front and in back of the three-dimensional viewport as well as positions that are left right below or above the volume. For two-dimensional clipping we used a four-digit binary region code to identify the position of a line endpoint relative to the viewport boundaries. For three-dimensional points we need to expand the region code to six bits. Each point in the description of a scene is then assigned a six-bit region code that identifies the relative position of the point with respect to the viewport. For a line endpoint at position x y z we assign the bit positions in the region code from right to left as bit 1 1 if X í Xĩ min left bit 2 1 ifx w right bit 3 1 ify yvm n. below bit 4 1 ify 5 y maxfabove bit 5 1 ifz z mm bont bit 6 1 ifz Z Tnax back For example a region code of 101000 identifies a point as above and behind the viewport and the region code 000000 indicates a point within the volume. A line segment can be immediately identified as completely within the viewport if both .
