The VERT_T3D function transforms a 3D array by a 4x4 transformation matrix and returns the transformed array. The 3D points are typically an array of polygon vertices that were generated by SHADE_VOLUME or MESH_OBJ.
This routine is written in the IDL language. Its source code can be found in the file
subdirectory of the IDL distribution.
Normally, a copy of Vertex_list is transformed and the original Vertex_list is preserved. If NO_COPY is set, however, then the original Vertex_List will be undefined after the call to VERT_T3D. Using the NO_COPY requires less memory.
Normally, when a [ x , y , z , 1] vector is transformed by a 4x4 matrix, the final homogeneous coordinates are obtained by dividing the x , y , and z components of the result vector by the fourth element in the result vector. Setting the NO_DIVIDE keyword will prevent VERT_T3D from performing this division. In some cases (usually when a perspective transformation is involved) the fourth element in the result vector can be very close to (or equal to) zero.
Set this keyword to a named variable that will hold receive the fourth element of the transformed vector(s). If Vertex_list is a vector then SAVE_DIVIDE is a scalar. If Vertex_list is an array then SAVE_DIVIDE is an array of n elements. This keyword only has effect when the NO_DIVIDE keyword is set.