User guide

247
Location Type or Attribute Type Description
geometry.poly.startIndex integer[ ] Is a list of indices defining the faces of a
mesh. For example, consider a cube. A cube
has a startIndex list size equal to the
number of faces in the mesh plus one. This
is because we must store the index of the
first point on the first face as well as the end
point of all the faces (including the first). So,
for example, the beginning of a cube’s
startIndex list may look like:
0 – 0
1 – 4
2 – 8
......
The indices for each polyon N are from
startIndex(N) to startIndex(N+1)-1. The
value at index 0 of the list tells us the first
face should start at index 0 in the
vertexList, the second value in the list tells
us the first face ends at index 3 (n-1).
This indicates the first face is a quadrilateral
polygon. The image below shows the
startIndex values of the first face in green.
The red text shows the indexed values of
the vertexList.
APPENDIX D STANDARD ATTRIBUTES | LOCATION TYPE CONVENTIONS