Entry 88

The window's scaler: sharp bilinear, so thin strokes keep one weight at any size

2026-09-24rendertest

Filescrates/piney-gs/src/lib.rs

The user reported that the desktop's font looked buggy: the icon labels (THE WORLD, MAILER, NEWS, ACCESSORY, AUDIO, DATA) had letters of uneven weight.

Not the game's drawing

• The native frame is clean. A 512 x 448 shot of the desktop, enlarged by whole pixels, shows every label crisp and even.
• The game samples nearest too. The labels are ccSprite cells. ccSprite::SetTag (0x0015c0c0) sends the TEX1 that SetTex (0x0015c2f0) copied from the texture's own data (+0x10 of the texture object) with MXL cleared. The desktop's textures set only MXL there, so the game samples them nearest, as desktop records and the port does.

The window

• What the presenter did. It stretched the frame to 4:3, letterboxed, with a plain bilinear sampler. The scale is not a whole number (1.5625 wide for a 512-wide frame in an 800-wide window).
• Why strokes went uneven. A 1-pixel stroke came out crisp where it lined up with the window's pixels and smeared over two greyer pixels where it did not.
• The fix. The present shader now scales sharp bilinear. Each frame pixel is a solid block, and only the one-window-pixel seam between two blocks is blended.
  • At a whole-number scale it samples texel centres exactly.
  • At scale 1 it is plain bilinear.
  • The scale per axis comes from the derivatives of the texel coordinate, so no uniform is needed.

This is a presentation choice, not the game's: a television blurs the analog picture instead.

Checked

• A new test on the GPU. present_keeps_thin_lines_whole draws twelve 1-pixel lines, 7 frame pixels apart, and presents them at 1600 x 1200 (3.125 wide). Every line keeps a pure-white peak.
• The test catches the old behaviour. With the plain sampler put back, the line at x 100 peaks at 219, and the test fails.
• The earlier test still passes. It is now written on a shared presented read-back helper and checks the letterbox and the colour values.