Graphics Reference
In-Depth Information
The following primitives can be drawn in OpenGL ES 3.0:
• Triangles
• Lines
• Point sprites
Triangles represent the most common method used to describe a
geometry object rendered by a 3D application. The triangle primitives
supported by OpenGL ES are
GL_TRIANGLES
,
GL_TRIANGLE_STRIP
, and
GL_TRIANGLE_FAN
. Figure 7-1 shows examples of supported triangle
primitive types.
v
1
v
3
v
3
v
4
v
1
v
5
v
0
v
4
v
2
v
2
v
0
GL_TRIANGLES
GL_TRIANGLE_STRIP
v
2
v
3
v
4
v
1
v
0
GL_TRIANGLE_FAN
Figure 7-1
Triangle Primitive Types
GL_TRIANGLES
draws a series of separate triangles. In Figure 7-1, two
triangles given by vertices (v
0
, v
1
, v
2
) and (v
3
, v
4
, v
5
) are drawn. A total
of
n/3
triangles are drawn, where
n
is the number of indices specified as
count
in
glDraw***
APIs mentioned previously.
GL_TRIANGLE_STRIP
draws a series of connected triangles. In the example
shown in Figure 7-1, three triangles are drawn given by (v
0
, v
1
, v
2
), (v
2
, v
1
, v
3
)
(note the order), and (v
2
, v
3
, v
4
). A total of
(n-2)
triangles are drawn, where
n
is the number of indices specified as
count
in
glDraw***
APIs.
