Entry 37

The ALTIMIT desktop runs from the disc: opening, main screen and mail

2026-09-23uirenderdecomptest

Filescrates/piney-desktopcrates/piney-drawcrates/piney-gscrates/piney-gamecrates/piney-inputtools/desktop_tables.pytools/test_desktop_rs.pydocs/engine/desktop.md

The user asked for more than a model viewer: a game viewer that boots into the ALTIMIT desktop and can be navigated. This entry is the first half of that:

• a runtime that runs a mode on the game's own clock and draws what the game would send the GS;
• the desktop itself, ported from DESKTOP.PRG.

A helper agent reverse engineered and ported the desktop. I wrote the runtime, the pad reading and the GS back end, and integrated the two.

Shape

The desktop is one of ccThMother's modes (request 3, DESKTOP.PRG, see the overview). The port keeps that seam: each part of the game is a mode that takes the pad and returns one frame's draw list.

• piney-input is ccPad::Read (0x00102d40) and SetAnalogStick:

  • pressed, released and repeat bits (a held combination repeats after 15 frames);
  • the left stick turned into D-pad bits by eighths.

  The game's quirks are kept: a stick with its raw y exactly 128 reads as down, and the up-right eighth presses right alone.

• piney-draw is what the EE sends the GS, as data:

  • primitives in frame-buffer pixels, with the ALPHA register, alpha test, Z test and SCISSOR;
  • model draws through VU1, per mmat, with the transparency, STROW, wrap and alpha reference the material packet carries;
  • run-time textures (the text ccKanji rasterises).

• piney-gs draws that on wgpu, in the game's 512 x 448 frame buffer:

  • it stays in the art's gamma, where the GS blends, and is shown at 4:3;
  • the ALPHA register's ((A - B) * C >> 7) + D becomes blend factors, with FIX as the blend constant;
  • TFX and TCC are in the shader, 0x80 = 1.0;
  • GS Z is larger-nearer;
  • a failing FB_ONLY alpha test gates only the Z write, done as two passes;
  • the GS's pixel-corner rule becomes a half-pixel shift.

  GPU tests check exact pixel coverage, MIX and ADD blending, the alpha test, scissor, MODULATE at 0x80 against the stored texture, and the presenter's letterbox and sRGB round trip.

• piney-game runs a mode on NTSC vertical blanks (59.94 a second), stepping it every frameRate of them. --shot plays scripted presses with no window.

• piney-desktop is Desktop_control and MailList_control, with the main executable's 2D and 3D draw paths they use (ccSprite, ccLayer, ccKanji, ccAnm::Draw, ccView).

• Content is read at run time from DESKTOP.PRG and SLUS_202.67 on the image: mail and reply text, wallpaper and music tables, the kanji fonts. The engine's own tables (glyph trims, escape colours, the blend table, mail reply links) are generated Rust from tools/desktop_tables.py.

What the desktop is

Most of it is 3D: xddesk01's models animated by ccAnm, seen through a camera (ANM_xddcamer). On top of that:

• 2D sprites from TEX_xddcurs1 for cursors, icons and window tiles;
• text as run-time PSMT4 textures.

2D is drawn through the default layer, which maps logical coordinates to GS ones with a 7/6 vertical stretch (XYOFFSET 0x7000, 0x7200).

Draw order. Layers go in ascending priority: 126 the 3D back layer, 127 kanji, 128 and 129 the mail windows, 240 font and fade. Within a layer, opaque models and sprites go in reverse call order, because both are prepended to the layer's list. Translucent mmats come after them, back to front by screen Z.

The saveData the desktop reads is the shared piney_data::save::SaveData:

• mailList / mailOrderList, through NewMail, ReadNewMail and CheckMail;
• the wallpaper and music choice;
• the assigned confirm and cancel buttons.

It also reads two ccEvent members, the operation lock operate and operateSet. The event engine writes them.

Checked

tools/test_desktop_rs.py runs the game's own functions in eemu against the port:

• SelectMode;
• DrawLogo, over 1,024 cases;
• NewIconDraw, over 700 frames, bit-exact;
• the mail list's MoveLine, SetLength and TimeAlphaCurDraw;
• ccKanji's layout against tools/font.py over the mail tables.

All pass. The camera was checked on eemu points: (0,0,0) lands at pixel (256, 224) and (100,0,0) at (257, 224).

Through piney-game and piney-gs:

• Opening. The icons fly in, with sound effects 0 and 1 and music 50 requested.
• Main screen. THE WORLD, MAILER, NEWS, ACCESSORY, AUDIO, DATA, each mode's panel, the ALTIMIT logo, wallpaper 49.
• Navigation. Down twice selects ACCESSORY with the cursor sound.
• Mail. With mails 4, 5 and 320 delivered (--mail; event 1 gives a new game these), the Mailer shows "You have 3 new mails.", the inbox lists CC Corporation, CC Corporation and Yasuhiko, and the first opens with the CC logo and its text.