acdream/src/AcDream.Core/Physics/PortalPlane.cs
Erik dc0341e85a fix(core): Phase B.3 — add centroid + radius bounds to PortalPlane crossing test
Two targeted fixes for user-reported movement bugs:

1. Wall bounce: PortalPlane.FromVertices now accepts ALL polygon vertices
   (not just 3) for accurate centroid + bounding radius. IsCrossing uses
   2D (XY) distance check with tight radius (no multiplier) to prevent
   wall faces from triggering false indoor transitions. Walking along a
   building wall no longer launches the player into the air.

2. Slope alignment: PlayerMovementController adds a slope-proportional
   Z bias when walking uphill (up to +0.8 on steep slopes, grounded
   only). Prevents feet from sinking into the visual terrain mesh on
   slopes where the physics sample point lags the render surface.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-12 19:08:46 +02:00

86 lines
3.5 KiB
C#

using System.Numerics;
namespace AcDream.Core.Physics;
/// <summary>
/// A portal plane derived from an EnvCell's CellPortal polygon.
/// Used to detect when a player crosses from one cell into another.
/// </summary>
public readonly record struct PortalPlane(
Vector3 Normal,
float D,
uint TargetCellId, // OtherCellId — the cell on the far side (0xFFFF = outdoor)
uint OwnerCellId, // the EnvCell that owns this portal
ushort Flags, // PortalFlags value
Vector3 Centroid, // center of the portal polygon in world space
float Radius) // bounding radius of the portal polygon
{
/// <summary>
/// Construct a PortalPlane from ALL polygon vertices (winding order of the
/// first three determines the normal). Centroid + radius are computed from
/// the full vertex set for accurate doorway bounds.
/// </summary>
public static PortalPlane FromVertices(
ReadOnlySpan<Vector3> vertices,
uint targetCellId, uint ownerCellId, ushort flags)
{
if (vertices.Length < 3)
throw new ArgumentException("Need at least 3 vertices", nameof(vertices));
var edge1 = vertices[1] - vertices[0];
var edge2 = vertices[2] - vertices[0];
var normal = Vector3.Normalize(Vector3.Cross(edge1, edge2));
float d = -Vector3.Dot(normal, vertices[0]);
// Centroid = average of ALL vertices.
var sum = Vector3.Zero;
foreach (var v in vertices) sum += v;
var centroid = sum / vertices.Length;
// Bounding radius = max distance from centroid to any vertex.
// NO padding — we rely on the tight radius to prevent wall-bounce.
float maxR = 0f;
foreach (var v in vertices)
{
float r = Vector3.Distance(centroid, v);
if (r > maxR) maxR = r;
}
return new PortalPlane(normal, d, targetCellId, ownerCellId, flags, centroid, maxR);
}
/// <summary>
/// Convenience overload for 3-vertex portals (backwards-compatible with
/// existing test call sites).
/// </summary>
public static PortalPlane FromVertices(
Vector3 v0, Vector3 v1, Vector3 v2,
uint targetCellId, uint ownerCellId, ushort flags)
{
ReadOnlySpan<Vector3> verts = stackalloc Vector3[] { v0, v1, v2 };
return FromVertices(verts, targetCellId, ownerCellId, flags);
}
/// <summary>
/// Returns true when the movement from <paramref name="oldPos"/> to
/// <paramref name="newPos"/> crosses this plane AND both positions are
/// within the portal's bounding radius of its centroid. Without the
/// radius check, infinite planes cause false transitions when walking
/// far from a doorway but on the same plane extension.
/// </summary>
public bool IsCrossing(Vector3 oldPos, Vector3 newPos)
{
// Quick reject: 2D (XY) distance from the portal centroid.
// Using XY-only prevents roof-level positions from triggering
// ground-floor doorways. The radius is kept tight (no multiplier)
// so only positions genuinely near the doorway opening pass.
float dx = MathF.Min(MathF.Abs(oldPos.X - Centroid.X), MathF.Abs(newPos.X - Centroid.X));
float dy = MathF.Min(MathF.Abs(oldPos.Y - Centroid.Y), MathF.Abs(newPos.Y - Centroid.Y));
float minDist2D = MathF.Sqrt(dx * dx + dy * dy);
if (minDist2D > Radius) return false;
float oldDist = Vector3.Dot(Normal, oldPos) + D;
float newDist = Vector3.Dot(Normal, newPos) + D;
return oldDist * newDist < 0f;
}
}