Due to the fact that the points renderer does not know for sure
which attributes will be used for rendering, it is now mandatory
to provide both vertex/fragment shaders for rendering AND hit
detection.
The hit detection shaders should expect having an `a_hitColor`
that they should return to allow matching the feature uid.
This will be all one eventually by shader builders under the hood.
Now most attributes will be custom ones defined by the user of the renderer.
The hit detection is broken for now and still has to be fixed.
Also it is not possible anymore to give a texture to the renderer,
this will have to be fixed as well.
The worker self object is simply cast to any to make sure typescript
does not complain.
Actual typecheck may be restored once the following issue is fixed:
https://github.com/microsoft/TypeScript/issues/20595
The worker currently works by receiving GENERATE_BUFFERS messages and
will send back the same kind of message, with the generated buffers
attached. All properties of the original message are kept, so that
when a GENERATE_BUFFERS message comes back to the main thread it
is possible to know what and how the buffers where generated.
This is typically used for the `projectionTransform` matrix, and
will also be necessary when working with tiles.
The worker receives a transferable array of instructions
and sends back two transferable arrays (vertex and index buffer).
The projection transform is also sent so that when the main thread
receives the buffers from the worker it also knows which projection to
apply when rendering the geometries.
