fix(mhfu-port): a ported PMO's clip is its largest scale component, as MHFU's are

The converter wrote 0, so the engine's sphere-frustum cull treated a port as a
point just above its feet: the model vanished as soon as that point left the
view, near the camera most of all.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: sp00ktober

docs/formats/pmo.md

@@ -22,7 +22,7 @@ from [mhff](https://github.com/svanheulen/mhff) by Seth VanHeulen.
 | 0x00 | `char[4]` | `pmo\0` |
 | 0x04 | `char[4]` | Version, `1.0\0` or `102\0` |
 | 0x08 | `u32` | Size: header, tables and geometry region. Bytes after it are the tail |
-| 0x0C | `f32` | Clip distance; MHFU sets the largest scale component |
+| 0x0C | `f32` | Cull-sphere radius before the entity's scale; MHFU sets the largest scale component, and 0 culls the model as a point |
 | 0x10 | `f32[3]` | Scale (MHFU): multiplies the dequantised positions |
 | 0x1C | `u16` | Mesh count |
 | 0x1E | `u16` | Material count |

packages/mhfu-port/src/mhfu_port/mesh.py

@@ -25,7 +25,6 @@
 BLEND = 0
 SHADOW = 0
 COLOR = 0xFFFFFFFF
-CLIP = 0.0
 NO_NORMAL = (0.0, 0.0, 0.0)
 """Written for a donor vertex that carries no normal."""
 
@@ -162,7 +161,8 @@ def build(skinned: Sequence[Skinned], scale: Vec3) -> pmo.Pmo:
     groups = [group(s, scale, material_of[s.part.texture]) for s in skinned]
     mesh = pmo.Mesh(groups, list(range(len(textures))), lighting=LIGHTING, blend=BLEND)
     materials = [pmo.Material(color=COLOR, shadow=SHADOW, texture=t) for t in textures]
-    return pmo.Pmo([mesh], materials, scale, CLIP)
+    # the engine's cull sphere (Pmo.clip): 0 culls the model as a point near its feet
+    return pmo.Pmo([mesh], materials, scale, max(scale))
 
 
 def group(skinned: Skinned, scale: Vec3, material: int = 0) -> pmo.Group:

packages/mhfu-port/tests/test_build.py

@@ -17,8 +17,8 @@
 
 PORTS = Path(__file__).parents[3] / "ports"
 BUILT = {
-    "brute_tigrex": "a882bf01daf07df844a07da32fd6ff87ed10c9ecb1fec7e1eb207172e6ca5e29",
-    "zinogre": "3a0b11b7556678c66364d3357107a8ee130677d2c5fde9a43c7dfd5f82948f12",
+    "brute_tigrex": "1082b88cfaeee3086020a6b02ff59101dec4af8653ff44a4b56373a90ae87fae",
+    "zinogre": "830a4c15ed67a8760c0462fa8bcd5fc6548ca0b00b090089bb6d382c5e5e2256",
 }
 """sha256 of each manifest's build: changes only with an intended change to the port."""
 HEAD = '[port]\nname = "t"\nhost_species = 75\npac = "t.bin"\n[source]\nmodel = 5248\n'

packages/mhfu-port/tests/test_mesh.py

@@ -131,7 +131,7 @@ def test_build():
     joint_of = {4: 1, 7: 2, 9: 3}
     built = mesh.build(skin.source(parts, joint_of), SCALE)
     back = fu.Pmo.from_bytes(built.to_bytes())
-    assert back == built and back.clip == mesh.CLIP and back.scale == SCALE
+    assert back == built and back.clip == max(SCALE) and back.scale == SCALE
     assert [m.texture for m in back.materials] == [2, 6]
     assert {(m.color, m.shadow) for m in back.materials} == {(mesh.COLOR, mesh.SHADOW)}
     assert back.meshes[0].materials == [0, 1] and back.meshes[0].lighting == mesh.LIGHTING
@@ -163,8 +163,8 @@ def test_palette_limit():
 
 
 DONORS = {  # model, geometry: groups, vertices, triangles, sha256 of our PMO on an identity map
-    "brute": (5248, 5249, 88, 2862, 2973, "cb0d830eb6c61a09"),
-    "zinogre": (5339, 5340, 181, 4336, 4426, "98b3869f594ce302"),
+    "brute": (5248, 5249, 88, 2862, 2973, "ccc9f32546fdfcbb"),
+    "zinogre": (5339, 5340, 181, 4336, 4426, "09fd2847cff33e01"),
 }
 
 

packages/mhp-formats/src/mhp_formats/pmo.py

@@ -536,7 +536,8 @@ class Pmo:
     scale: Vec3 = (1.0, 1.0, 1.0)
     """Multiplies the dequantised positions."""
     clip: float = 0.0
-    """Clipping distance; MHFU sets it to the largest scale component."""
+    """Cull-sphere radius before the entity's scale, centred half a `scale.y` up; MHFU sets it to
+    the largest scale component, and 0 culls the model as a point."""
     tail: bytes = b""
     """Bytes after the size the header declares (a standalone file pads to 0x800)."""