This simplifies python code.
When we call a method like shader.uniform_float("color", (1,1,1,1)),
we expect the shader's uniform to be updated regardless of whether the
shader is bound or not.
And `batch.draw()` already calls `GPU_shader_bind` inside.
Differential Revision: https://developer.blender.org/D15929
Adds an example python script to the documentation for the 3D_IMAGE shader.
The **use-case** is to draw textures with 3D vertex positions, in XR views as well as non-XR views (in a simpler manner).
**Testing**: I've tested that this compiles and works on my Macbook (with the example python script included in this change). I don't have access to a Windows or Linux machine right now, but this change doesn't look platform-specific and no new glsl shaders have been added or edited by this change. I'll try to get access to a Windows machine, but if someone does have one, I'd be really grateful if they could try this change. Thanks!
**Problem addressed**: The existing 2D_IMAGE shader (exposed in the python API) gets near-clipped when drawn in the
XR view, regardless of the near-clip settings. Additionally, the 2D_IMAGE shader only accepts 2D
positions for the image vertices, which means drawing textures in 3D requires providing
2D coordinates and then pushing a transform-rotate-scale matrix to the GPU, even for
non-XR (i.e. WINDOW) views. The 3D_IMAGE shader is simpler: it accepts 3D vertex positions, and doesn't require
any additional work by the scripter.
**Workaround**: The current workaround is to use custom shaders in the python script.
**Non-intrusive change**: No new glsl shaders were added. This change just bundles two existing shaders: the vertex shader used
by the 3D_IMAGE_MODULATE_ALPHA shader, and the fragment shader used by the 2D_IMAGE shader.
Reviewed By: #eevee_viewport, jbakker
Differential Revision: https://developer.blender.org/D14832