OpenGL 4.2 (Compatibility Profile) - April 27, 2012

2.6. BEGIN/END PARADIGM 26
2
4
6
2 3
6 7
1
3
5
1
4 5
8
(a)
(b)
Figure 2.5. (a) A quad strip. (b) Independent quads. The numbers give the sequencing
of the vertices between Begin and End.
tion 2.16). If a geometry shader is not active, the adjacent vertices are ignored.
They are generated with mode LINES_ADJACENCY.
A line segment is drawn from the 4i + 2nd vertex to the 4i + 3rd vertex for
each i = 0, 1, . . . , n − 1, where there are 4n + k vertices between a Begin and
End pair. k is either 0, 1, 2, or 3; if k is not zero, the final k vertices are ignored.
For line segment i, the 4i + 1st and 4i + 4th vertices are considered adjacent to the
4i + 2nd and 4i + 3rd vertices, respectively (see figure 2.6).
Line Strips with Adjacency
Line strips with adjacency are similar to line strips, except that each line segment
has a pair of adjacent vertices that can be accessed by a geometry shader. If a
geometry shader is not active, the adjacent vertices are ignored. They are generated
with mode LINE_STRIP_ADJACENCY.
A line segment is drawn from the i + 2nd vertex to the i + 3rd vertex for each
i = 0, 1, . . . , n − 1, where there are n + 3 vertices between a Begin and End pair.
If there are fewer than four vertices, all vertices are ignored. For line segment i,
the i + 1st and i + 4th vertex are considered adjacent to the i + 2nd and i + 3rd
vertices, respectively (see figure 2.6).
Triangles with Adjacency
Triangles with adjacency are similar to separate triangles, except that each triangle
edge has an adjacent vertex that can be accessed by a geometry shader. If a
geometry shader is not active, the adjacent vertices are ignored. They are generated
with mode TRIANGLES_ADJACENCY.
OpenGL 4.2 (Compatibility Profile) - April 27, 2012