Well, they are not Blitz specific. More general 3D related.
Normals are used in 3D calculations such as in checking what direction a polygon is facing - ie which way a polygon's normal is pointing.
The 'Blitz' definition is 'Recalculates all normals in a mesh. This is necessary for correct lighting if you have not set surface normals using 'VertexNormals' commands.'
In Blitz you generally use normals for lighting reasons - but you could use them for backface culling, etc too.
Here is a link regarding the z-buffer:
http://www.toymaker.info/Games/html/z_buffer.html
Blitz also has a wbuffer command. Type wbuffer into Blitz3D - click on the word, then press F1 for a bit of info.
You are best Googling your two questions as they are not Blitz-based. I believe though that there are quirks to the z-buffer in Blitz3D.
Normals are used in 3D calculations such as in checking what direction a polygon is facing - ie which way a polygon's normal is pointing.
The 'Blitz' definition is 'Recalculates all normals in a mesh. This is necessary for correct lighting if you have not set surface normals using 'VertexNormals' commands.'
In Blitz you generally use normals for lighting reasons - but you could use them for backface culling, etc too.
Here is a link regarding the z-buffer:
http://www.toymaker.info/Games/html/z_buffer.html
Blitz also has a wbuffer command. Type wbuffer into Blitz3D - click on the word, then press F1 for a bit of info.
You are best Googling your two questions as they are not Blitz-based. I believe though that there are quirks to the z-buffer in Blitz3D.