Graphics Programs Reference
In-Depth Information
+ "}";
As explained in the section “GLSL”, every fragment shader must explicitly declare
a default precision for
float
types, such as
vec4
, which is why there is extra code
at the top of fragment shader in
Listing 3-22
.
(Refer back to that topic for more on
the basics of data types.)
Triangle Primitive
Like a line primitive, rendering a triangle primitive (
Figure 3-13
)
requires appropri-
ately setting the arguments of the
glDrawArrays
function. We must specify the
mode
as
GLES20.GL_TRIANGLES
and the
count
as a multiple of 3 (you get an
imaginary triangle if you set the
count
to 0!).
Figure 3-13
.
Rendering triangle using glDrawArrays
Rendering a triangle primitive is left as an exercise for you, but, in case you find
this difficult, you can import the archive file
gltriangle.zip
from the source
code for this chapter. This will load the
GL TRIANGLE
application into your Eclipse
workspace.
As previously mentioned, in ES 2.0 we can use a combination of the same type of
primitives to render various objects. Now, let's look at rendering a rectangle using
two triangle primitives.
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