This handles the case where bypass_vs is set, but vertices need to go
through the pipeline for some reason - eg unfilled polygon mode.
Demonstrates how to drive the pipeline from inside one of these things.
Leaving it until 'run' is bad as the primitive is pretty much state
for some drivers and so needs to get set early. In some drivers
this is used to determine things like vertex format, etc -- by the
time we get to 'run', it's too late to change this.
- Reduce the number of changes to the normal vertex ordering
- Assume that the hardware knows how to do this in the standard case.
- Add support to the passthrough vcache path.
Trying to put a structure in place that we can actually optimize.
Initially just implementing a passthrough mode, this will fairly soon
replace all the vertex_cache/prim_queue/shader_queue stuff that's so
hard to understand...
Split the vertex processing into a couple of distinct stages:
- Frontend
- Prepares two lists of elements (fetch and draw) to be processed
by the next stage. This stage doesn't fetch or draw vertices, but
makes the decision which to draw. Multiple implementations of this
will implement different strategies, currently just a vcache
implementation.
- MiddleEnd
- Takes the list of fetch elements, fetches them, runs the vertex
shader, cliptest, viewport transform on them to produce a
linear array of vertex_header vertices.
- Passes that list of vertices, plus the draw_elements (which index
into that list) onto the backend
- Backend
- Either the existing primitive/clipping pipeline, or the vbuf_render
hardware backend provided by the driver.
Currently, the middle-end is the old passthrough code, and it build hardware
vertices, not vertex_header vertices as above. It may be that passthrough
is a special case in this respect.
