re: the UI blend mode is MEASURED -- the frames are drawn ADDITIVE

Closes the one route t32-blend-mode-not-on-disc.md left open: the executable's
draw path. Canary's UI draw capture now logs RB_BLENDCONTROL0 per draw, and the
game was driven to the main menu and to EXTRAS with F10 at each.

The title-side UI uses two blend states and ONE pixel shader:

  0x07010701  src=ONE dst=1-SRC_ALPHA  alpha-over (premultiplied)
              ptbase, pteff05, the fade quad, ptmsg, ptmsg2, pttitle, buttons
  0x01010101  src=ONE dst=ONE          ADDITIVE
              ptframe1, ptframe2, ptframe3, pteff20, both rotated sweep strips

Two controls, both run before the result was read:

* the NDC->pixel conversion that identifies a draw by its quad size reproduces
  1134 and 1303 px for the two rotated sweep strips -- numbers measured by a
  different tool in a different session -- on BOTH screens. The tool prints
  PASS/FAIL and disclaims its own output on FAIL.
* pixel shader 0xE59B2B3DA4AA9008 is used with BOTH states, 12 draws additive
  and 18 alpha-over. ptframe1 and ptbase run the same shader; only the blend
  register differs. So this is a blend result, not a shader result.

This confirms the port's independent measurement -- it solved the composite per
pixel from two backgrounds and found additive halves alpha-over's error on both
frames -- by a route with nothing in common with it.

So the blend is no longer authored: 'any blend you choose is authored' was true
of the disc and is not true of the game. What is still unknown is which field
selects it; elements sharing a mode are batched into one draw call, so the
selection happens before the draw.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v

tools/re-capture/ui_blend_map.py

@@ -92,12 +92,19 @@ def main():
             w = (max(xs) - min(xs)) / 2 * W
             h = (max(ys) - min(ys)) / 2 * H
             heights.append(h)
-            best, bd = "-", 1e9
+            # A sprite is drawn at its native size or at 2x: the screen is
+            # 1280x720 and the design space is 640x360, so `ptbase` (640x360)
+            # covers the screen while `pteff05` (1280x720) is 1:1. Both are
+            # tried and the scale is reported, because guessing one would
+            # silently mis-name half the draws.
+            best, bd, bs = "-", 1e9, 1
             for n, (sw, sh) in sizes.items():
-                d = abs(sw - w) + abs(sh - h)
-                if d < bd:
-                    best, bd = n, d
-            tag = best if bd <= 6 else "(no match, nearest %s off %.0f)" % (best, bd)
+                for sc in (1, 2):
+                    d = abs(sw * sc - w) + abs(sh * sc - h)
+                    if d < bd:
+                        best, bd, bs = n, d, sc
+            tag = ("%s @%dx" % (best, bs)) if bd <= 8 else \
+                  "(no match, nearest %s @%dx off %.0f)" % (best, bs, bd)
             print("%4d %4d %4d  0x%08X %-20s %7.1f x %7.1f   %s"
                   % (idx, prim, nidx, raw, blend_name(raw), w, h, tag))
     tall = sorted(h for h in heights if h > 900)