Motocross Madness demo

Test route

The browser build can reach a live race without Wine. With a persisted profile, the reliable 640x480 guest-coordinate route is:

1. (310,441) captures the mouse over the existing-profile screen.
2. (445,45) twice enters the main menu and Single Player Event.
3. (350,442) advances through track selection, rider selection, and Start.

The CLI-driven Puppeteer probe used during the 2026-08-30 investigation waited 45 seconds after Start in cooperative mode and 60 seconds in true browser Worker mode. Both reached UI id 104 and rendered the quarry, rider, HUD, and attached 16-bit Z surface. The Worker run was served with COOP/COEP isolation and reported hasWorker:true; its loading phase is substantially slower but is not stuck.

Rendering findings

• MCM submits legacy D3DLVERTEX records with the documented eight-DWORD, 32-byte layout: XYZ, reserved, diffuse, specular, U, V. Treating the record as 28 bytes shifts every vertex after the first and reads the reserved DWORD as diffuse colour.
• Direct DrawPrimitive receives projected vertices that can straddle the near plane. Drawing those triangles without reconstructing and clipping their homogeneous coordinates leaves camera-near holes containing old menu pixels. Clipping at z=0, then reprojecting the generated vertices, produces continuous terrain from the horizon to the rider. A positive reciprocal W does not make a vertex near-plane-visible: MCM also produces vertices with rhw > 0 but z/w < 0. Classifying only by RHW sends those triangles to the raw rasterizer and creates giant landscape wedges and repeated billboard labels. The first correction classified those vertices correctly but still intersected every rejected edge with z=0. That is also insufficient: when a negative-RHW endpoint retains positive clip-z, the edge enters through the far plane z=w, and a forced near intersection collapses the visible part into a fan. The direct path now clips a bounded convex polygon against both homogeneous depth inequalities, z>=0 and z<=w; together they imply a positive W. Pre-transformed UI records with rhw=0 retain the raw path because their original homogeneous coordinates cannot be reconstructed.
• MCM enables D3DRENDERSTATE_COLORKEYENABLE and uses packed 16-bit source colour keys. A keyed sample is discarded before both colour and Z writes.
• MCM owns both a 640x480 race viewport and a 128x128 texture viewport on the same Direct3D device. SetViewport configures the addressed viewport object; it must not replace the device's cached transform rectangle when that object is inactive. Doing so changes the projection scale from (320,240) to (64,64) and compresses the rider and terrain toward the upper-left while long camera-near polygons fan across the rest of the frame. Selecting a viewport with SetCurrentViewport now restores that object's saved rectangle.
• The HUD uses paired system/video-memory surfaces. For example, the traced 64x64 gauge source and destination were slots 406 and 407 with identical pixels. IDirect3DTexture::Load must copy the source-key flag and packed key to the destination, converting the key when the surface formats differ. Pixel-only loads leave the destination texture's 0xf81f magenta background visible even though the renderer implements colour-key discard correctly.
• DirectDraw Blt must apply DDBLT_KEYSRC to nearest-neighbour stretches as well as equal-size copies. MCM exercises that path for scaled 2D art.

The focused coverage is in test/test-d3dim-indexed-texture.js and test/test-directdraw-cursor-background-restore.js. The verified final race screenshots from the investigation were /private/tmp/mcm-fixed-coop2-final-wait-45000.png and /private/tmp/mcm-fixed-worker-final-wait-60000.png.