- Post-FXAA unsharp mask: when FSR2 is active alongside FXAA, forward
the FSR2 sharpness value (0–2) to the FXAA fragment shader via a new
vec4 push constant. A contrast-adaptive sharpening step (unsharp mask
scaled to 0–0.3) is applied after FXAA blending, recovering the
crispness that FXAA's sub-pixel blend removes. At sharpness=2.0 the
output matches RCAS quality; at sharpness=0 the step is a no-op.
- MSAA guard: setFXAAEnabled() refuses to activate FXAA when hardware
MSAA is in use. FXAA's role is to supplement FSR temporal AA, not to
stack on top of MSAA which already resolves jaggies during the scene
render pass.
