Graphics Reference
In-Depth Information
As you read through this topic, you will look at a lot of shaders. If you
ever start developing your own OpenGL ES 3.0 application, chances
are that you will write a lot of shaders. By now, you should understand
the fundamental concepts of what a shader does and how it fits in the
pipeline. If not, please go back and review Chapter 1, “Introduction to
OpenGL ES 3.0,” where we covered the pipeline and described where
vertex and fragment shaders it within it.
What we want to look at now is what exactly makes up a shader. As you
have probably already observed, the syntax bears great similarity to that
seen in the C programming language. If you can understand C code, you
likely will not have much difficulty understanding the syntax of shaders.
However, there are certainly some major differences between the two
languages, beginning with the version specification and the native data
types that are supported.
The first line of your OpenGL ES 3.0 vertex and fragment shaders will
always declare a shader version. Declaring the shader version informs the
shader compiler which syntax and constructs it can expect to be present
in the shader. The compiler checks the shader syntax against the declared
version of the shading language used. To declare that your shader uses
version 3.00 of the OpenGL ES Shading Language, use the following
syntax:
#version 300 es
Shaders that do not declare a version number are assumed to use revision
1.00 of the OpenGL ES Shading Language. Revision 1.00 of the shading
language is the version that was used in OpenGL ES 2.0. For OpenGL
ES 3.0, the specification authors decided to match the version numbers
for the API and Shading Language, which explains why the number
jumped from 1.00 to 3.00 for OpenGL ES 3.0. As described in Chapter 1,
“Introduction to OpenGL ES 3.0,” the OpenGL ES Shading Language
3.0 adds many new features, including non-square matrices, full integer
support, interpolation qualifiers, uniform blocks, layout qualifiers, new
built-in functions, full looping, full branching support, and unlimited
shader instruction length.
