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PlayStation RSD, Psy-Q PLY, and MAT sidecars

QtMeshEditor treats PlayStation RSD (.rsd) as a small descriptor that points at a mesh and optional texture/material sidecars. The mesh is usually a TMD (.tmd) or a Sony Psy-Q PLY (.ply). These are not Stanford PLY files: Psy-Q PLY uses an @PLY… header, separate vertex and normal tables, and face lines with independent vertex and normal indices.

RSD (.rsd)

An RSD file lists paths or basenames for:

  • Model — typically .tmd or Psy-Q .ply
  • Texture / TIM — PlayStation 4-bit / 8-bit / 16-bit images (.tim), applied when loading through the RSD path
  • Material — optional .mat companion with per-face or material parameters used by classic toolchains

Importing .rsd resolves those references, loads the mesh (TMD or Psy-Q PLY), and attaches TIM-driven materials when possible. Exporting to .rsd writes the descriptor plus best-effort sidecar filenames (.tmd / .tim / etc.) next to the output.

Psy-Q PLY import

  1. Header — e.g. @PLY940102 (variant digits allowed).
  2. Counts — one line: nV nN nF (number of positions, normals, faces). Positions and normals are separate pools; nV and nN need not match.
  3. Vertices — nV lines of x y z (model space; import applies the editor’s Psy-Q PLY world transform).
  4. Normals — nN lines of nx ny nz.
  5. Faces — per face:
    • 0 v0 v1 v2 pad n0 n1 n2 pad — triangle
    • 1 v0 v1 v2 v3 n0 n1 n2 n3 — quad (PlayStation-style split into two triangles internally is (v0,v1,v2) and (v1,v2,v3))

Corner attributes (position + normal + optional colour) are welded on import so Ogre’s indexed triangle list matches shading boundaries.

When the file encodes quads or higher polygons, the importer records logical face sizes and stores n-gon topology on the mesh (qtme.faces.*, same mechanism as FBX n-gons). That preserves artist intent for later export.

Psy-Q PLY export

Export walks the renderable mesh and writes:

  1. Welded position table — unique positions after quantized welding (fixed-point style bucket in world space).
  2. Welded normal table — independent pool: same quantization, but normals deduplicate separately from positions. Many corners can share one quantized normal, so nN is often smaller than nV, even when the source file listed more normal lines. That is expected and usually means redundant normals collapsed to one index after quantization.
  3. Face lines — triangles (0 …) or quads (1 …) with separate vertex and normal indices per corner.

Why fewer normals than the original file is OK

Original Psy-Q assets often duplicate the same direction many times with tiny float differences. After import, Ogre may still carry one normal per corner. On export, each corner’s normal is quantized and welded into the normal pool. If four corners of a flat quad all map to the same quantized (nx,ny,nz), the file shows one normal line and four indices pointing at it — fewer lines than a verbose original, but equivalent shading for that polygon.

qtme.faces vs heuristic quad restore

  • If qtme.faces.0 (etc.) is present — for example after importing a Psy-Q file with quad lines, or after editing in mesh mode — export uses those n-gons directly. Quads stay quads; larger n-gons are fanned to triangles in the file as required by the format.
  • If that metadata is missing — e.g. a mesh that only exists as two triangles in the index buffer — export runs a heuristic: pairs of adjacent triangles that form a convex quad, share an edge in the PS1 (v0,v1,v2)+(v1,v2,v3) pattern, and have nearly parallel face normals (dot ≥ 0.94) are merged back into a single quad line. That restores many flat quads lost when DCC tools triangulate, without inventing quads across sharp creases.

Together, explicit n-gon metadata and the merge heuristic are why round-trips through QtMeshEditor often match or improve on the original polygon layout: fewer spurious triangle pairs, and normal pools that collapse true duplicates after quantization.

MAT sidecars

When vertex colours exist on all submeshes, Psy-Q PLY export can optionally emit per-face colours (for tooling that builds a .mat from face colours). RSD export paths wire this where the pipeline supplies a colour buffer.

See also

  • PS1PLY.h / PS1PLY.cpp — detection, import, export, merge heuristic
  • PS1RSD module — RSD parse/load/save and sidecar resolution