API Docs: gpu api introduction + examples

doc/python_api/examples/gpu.1.py

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+"""
+Geometry Batches
+++++++++++++++++
+
+To draw geometry using the gpu module you need to create a :class:`gpu.types.GPUBatch` object.
+Batches contain a sequence of points, lines or triangles and associated geometry attributes.
+
+A batch can be drawn multiple times, so they should be cached whenever possible.
+This makes them much faster than using the legacy `glBegin` and `glEnd` method, which would recreate the geometry data every time.
+
+Every batch has a so called `Vertex Buffer`.
+It contains the attributes for every vertex.
+Typical attributes are `position`, `color` and `uv`.
+Which attributes the vertex buffer of a batch contains, depends on the shader that will be used to process the batch.
+
+Shaders
++++++++
+
+A shader is a small program that tells the GPU how to draw batch geometry.
+There are a couple of built-in shaders for the most common tasks.
+Built-in shaders can be accessed with :class:`gpu.shader.from_builtin`.
+Every built-in shader has an identifier (e.g. `2D_UNIFORM_COLOR` and `3D_FLAT_COLOR`).
+
+Custom shaders can be used as well.
+The :class:`gpu.types.GPUShader` takes the shader code as input and compiles it.
+Every shader has at least a vertex and a fragment shader.
+Optionally a geometry shader can be used as well.
+
+.. note::
+   A `GPUShader` is actually a `program` in OpenGL terminology.
+
+Shaders define a set of `uniforms` and `attributes`.
+**Uniforms** are properties that are constant for every vertex in a batch.
+They have to be set before the batch but after the shader has been bound.
+**Attributes** are properties that can be different for every vertex.
+
+The attributes and uniforms used by built-in shaders are listed here: :class:`gpu.shader`
+
+A batch can only be processed/drawn by a shader when it provides all the attributes that the shader specifies.
+
+Examples
+++++++++
+
+To try these examples, just copy them into Blenders text editor and execute them.
+To keep the examples relatively small, they just register a draw function that can't easily be removed anymore.
+Blender has to be restarted in order to delete the draw handlers.
+"""