Implement a render context without state sets

[pmiddend]

The idea here is to get rid of: renderer.state(list_of_states);, simply because implementing backends for that is very tedious and not flexible enough.

Instead, we should have virtual functions for states. For example, instead of:

context.state(
    (fog_mode::linear)
    (fog_start = foo)
    (fog_end = bar)
    (...)
);

we should have

context.fog_properties(
    fog_properties(
        fog_mode::linear,
        fog_start::foo,
        fog_end::bar
    )
);

Using this, we can more easily implement:

• pure GL3/DX11 contexts, since we can now properly separate ffp states from non-ffp states
• "ffp fallback contexts", meaning contexts which use a shader as backend and might even have more properties than the ffp context (such as specular maps)
• an inheritance hierarchy with render contexts (ffp_fallback context derives from ffp context which in turn derives from core context)

Disadvantages of this approach are:

• no push_state/pop_state (might be possible, but is extremely difficult to implement)

[pmiddend]

List of all core states:

• int/uint:
  • stencil_ref
  • stencil_mask
  • stencil_write_mask
• enums:
  • cull_mode
  • depth_func
  • dest_blend_func
  • source_blend_func
  • stencil_func
  • stencil_op
  • stencil_op_value
  • draw_mode
• bool:
  • enable_alpha_blending
  • enable_scissor_test
  • write_to_depth_buffer
  • write_color

List of all ffp states:

• enums
  • alpha_func
  • fog_mode
• bool
  • enable_lighting
  • enable_point_sprites (really?)
  • local_viewer
  • normalize_normals
• color
  • ambient light color
  • fog color
• float:
  • alpha_test_ref
  • fog_start
  • fog_end
  • fog_density

List of core "pseudostates" (states not in renderer::state, but already in the context in the described fashion):

• vertex buffer (multiple possible at once)
• vertex declaration
• texture filter
• texture address mode
• texture (multiple possible at once, via index)
• cg texture
• cg program

List of ffp "pseudostates":

• material
• light (enabled flag and light::object)
• clip plane (enabled flag and clip_plane)
• texture stage operation
• texture stage arg
• world, texture and projection transform matrix

(alpha_func moved to ffp enums by Freundlich)

[pmiddend]

The whole issue might be something we should test in a smaller environment, first. I'm going to implement two scenic::render_contexts, one using the ffp, one using Cg. This could serve as a hint as to how the interface is going to look like.

[cpreh]

In D3D11, the following state sets are available (only the states that are currently implemented in sge are listed):

• blend states:
  • alpha blending enabled
  • color and alpha, source and destination blend
  • write color
• depth stencil states:
  • depth and stencil enabled
  • depth and stencil write mask
  • depth func
  • stencil op
• rasterizer state:
  • fill mode
  • cull mode
  • enable scissor test
  • enable multi sampling
• sampler state
  • texture filter
  • texture address mode