Q: Some of the blocks in a MDB file have a 32-bit field in front of the vertex count field, which we assume is a flag bit vector. In most cases it has a value of 0, but occasionally some bits are set. What do they indicate?
A: The bitflags are as follows for skin and rigid packets:
const DWORD NWN2_ALPHA_TEST = 1 << 0;
const DWORD NWN2_ALPHA_BLEND = 1 << 1; // #### SHOULD NOT BE USED
const DWORD NWN2_ADDITIVE_BLEND = 1 << 2; // #### SHOULD NOT BE USED
const DWORD NWN2_ENVIRONMENT_MAPPED = 1 << 3;
const DWORD NWN2_CUTSCENE_MESH = 1 << 4;
const DWORD NWN2_GLOW = 1 << 5;
const DWORD NWN2_NO_CAST_SHADOWS = 1 << 6;
const DWORD NWN2_PROJECTED_TEXTURES = 1 << 7;
Most of them are pretty straightforward. The projected texture flag means that the model will accept UI projected textures such as the spell targeting cursor.