Intel 815 Manuel D’Utilisation

206  

 

In Variable vertex format, a position mask is sent to indicate the present of X, Y, Z, and 1/W parameters. 
If 1/W (RHW) is declared not present in the vertex packet, hardware forces 1/w equal to 1. In the case Z 
is declared not present, the Z value of the last triangle from the last vertex instruction packet will be used 
for the triangles in this packet. 

A Z bias value can be included in the vertex instruction packet as a per polygon basis. This value is a 
floating point number that ranges from -1 to 1. The Z bias value is added to the Z value and then clamped 
to between 0 to 1 before primitive setup calculation. In triangle or line primitive type, Z bias of the last 
vertex (3

rd

 in triangle, 2

nd

 in line) will be used to add to all the vertices of the primitive and the Z bias 

value on the other vertices will be ignored. In triangle strip and fan, the Z bias value on the 3

rd

 vertex will 

be used for the first triangle and the Z bias value on subsequent vertex which defined a triangle will be 
used for that triangle. 

 

0 31:29 

Client : 03h – Rendering Engine 

 28:24 

Rendering Primitive : 1Fh 

 23 

Reserved: 00h 

 22:18 

Primitive Type: 

0h = Triangle or Triangle List 
1h = Triangle Strip 
2h = Triangle Strip with Reverse Winding Order 
3h = Triangle Fan 
4h = Polygon(Triangle Fan with Common Flat Shaded Vtx) 
5h = Line or Line List 
6h = Line Strip 
7h = Rectangle or Rectangle List (must be axis aligned) 
8h–1Fh = Reserved 

 17:0 

DWord Count  

1 N/A 

Primitive[0] Vertex[0]: GFXVERTEX 

 N/A 

Primitive[0] Vertex[1]: GFXVERTEX 

 

: 

                      : 

Variable N/A 

Primitive[n] Vertex[2]: GFXVERTEX 

Last DWORD of last vertex of last primitive 

Refer to GFXVERTEX section for details on defining primitive vertex.