feat(physics): Task 2 — true sphere collision primitive (CSphere::intersects_sphere)
Setup.Spheres were previously coerced to short cylinders (CylHeight=2*r), which is geometrically wrong: a cylinder has flat caps; a sphere does not. This ported CSphere::intersects_sphere (0x00537A80) so sphere-typed shadow entries are tested as spheres — 3-D distance, no height clamping. Changes: - ShadowObjectRegistry.cs: added ShadowCollisionType.Sphere (enum value 2). The BuildFloodSpheres anyCyl dedup at :232 is unaffected: only Cylinder sets anyCyl=true; Sphere shapes fall through to the BSP-fallback path (anyCyl=false → included), which is correct. - ShadowShapeBuilder.cs: FromSetup now emits ShadowCollisionType.Sphere (CylHeight=0) for Setup.Spheres instead of a short Cylinder. - CollisionPrimitives.cs: added SweptSphereHitsSphere — quadratic swept solve ported from ACE Sphere.cs::FindTimeOfCollision, which is a C# port of retail's CSphere::intersects_sphere @ 0x00537A80. Sign convention confirmed against the decomp: retail negates the root to produce a forward t ∈ (0,1]. - TransitionTypes.cs: added Sphere narrow-phase branch between BSP and Cylinder in FindObjCollisionsInCell; uses 3-D distance for overlap (not XY-only). Added SphereCollision() method implementing the 3-D wall-slide response. Updated diagnostic logging at :2734 to cover Sphere. - Updated ShadowShapeBuilderTests for new Sphere type assertion. - New SphereIntersectsSphereConformanceTests: 9 geometrically-anchored cases (head-on, tangent, perpendicular-miss, lateral-near-miss, sweep-away, beyond-step, degenerate-zero-sweep, already-overlapping, vertical-sweep). Retail oracle: CSphere::intersects_sphere @ 0x00537A80 (named-retail); ACE Sphere.cs::FindTimeOfCollision (C# port, cross-confirmed). Build: 0 errors, 10 warnings (pre-existing). Tests: 1576 pass / 0 fail / 2 skip (1578 total). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Erik
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7 changed files with 609 additions and 16 deletions
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@ -634,6 +634,115 @@ public static class CollisionPrimitives
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return (offset - dist) / denom;
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}
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// -----------------------------------------------------------------------
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// 8b. SweptSphereHitsSphere — CSphere::intersects_sphere narrow-phase
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// -----------------------------------------------------------------------
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/// <summary>
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/// Returns <see langword="true"/> when a moving sphere first intersects a
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/// stationary sphere within the movement step, and the parametric contact
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/// time <paramref name="t"/> is in (0, 1].
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///
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/// <para>
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/// Ported from <c>CSphere::FindTimeOfCollision</c> in
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/// <c>ACE.Server/Physics/Sphere.cs</c>, which is a line-for-line C# port
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/// of retail's <c>CSphere::intersects_sphere @ 0x00537A80</c> (the
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/// "collide ≠ 0, not creature" branch at <c>0x00537B8C</c>).
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/// </para>
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///
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/// <para>
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/// The retail quadratic (from the decomp):
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/// <list type="bullet">
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/// <item><c>distSq = |movement|²</c> — squared length of sweep vector.</item>
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/// <item><c>gap = |spherePos|² − radSum²</c> — positive when centers
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/// are separated, negative when already overlapping.</item>
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/// <item><c>similar = −dot(spherePos, movement)</c> — projection of the
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/// separation onto the movement direction.</item>
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/// <item><c>disc = similar² − gap·distSq</c> — discriminant.</item>
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/// <item>Pick the earlier root, normalise by <c>distSq</c>.</item>
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/// </list>
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/// </para>
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///
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/// <para>
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/// Returns <see langword="false"/> when the spheres are already overlapping
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/// (<c>gap < ε</c>), the discriminant is negative (miss), the movement
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/// is degenerate, or the contact time is outside (0, 1].
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/// </para>
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/// </summary>
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/// <param name="moverCenter">
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/// World-space centre of the moving sphere at the START of the step.
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/// </param>
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/// <param name="moverRadius">Radius of the moving sphere.</param>
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/// <param name="sweepDelta">
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/// Movement vector: <c>checkPos − currCenter</c>.
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/// </param>
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/// <param name="targetCenter">
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/// World-space centre of the stationary target sphere.
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/// </param>
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/// <param name="targetRadius">Radius of the target sphere.</param>
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/// <param name="t">
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/// On success: parametric fraction of <paramref name="sweepDelta"/> at
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/// which the sphere surfaces first touch (in (0, 1]).
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/// Undefined on failure.
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/// </param>
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/// <returns>
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/// <see langword="true"/> when the mover hits the target within this step.
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/// </returns>
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public static bool SweptSphereHitsSphere(
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Vector3 moverCenter, float moverRadius,
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Vector3 sweepDelta,
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Vector3 targetCenter, float targetRadius,
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out float t)
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{
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t = 0f;
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// movement = sweepDelta (mover travels from moverCenter by this vector)
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// spherePos = targetCenter − moverCenter (target relative to mover start)
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// radSum = combined radius for first-surface-contact
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float radSum = moverRadius + targetRadius;
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float mx = sweepDelta.X, my = sweepDelta.Y, mz = sweepDelta.Z;
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float distSq = mx * mx + my * my + mz * mz;
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if (distSq < EpsilonSq)
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return false; // degenerate sweep (stationary mover)
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float sx = targetCenter.X - moverCenter.X;
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float sy = targetCenter.Y - moverCenter.Y;
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float sz = targetCenter.Z - moverCenter.Z;
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// gap = |spherePos|² − radSum²
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// Positive → centers are separated (the common case).
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// Negative → already overlapping → treat as no forward collision (retail returns -1).
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float gap = sx * sx + sy * sy + sz * sz - radSum * radSum;
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if (gap < EpsilonSq)
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return false; // already overlapping — use static test separately
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// similar = −dot(spherePos, movement)
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// Positive when the sphere is in FRONT of us (moving toward it).
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float similar = -(sx * mx + sy * my + sz * mz);
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// discriminant = similar² − gap · distSq
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float disc = similar * similar - gap * distSq;
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if (disc < 0f)
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return false; // ray misses the combined-radius sphere entirely
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float cDist = MathF.Sqrt(disc);
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// Pick the nearer root. ACE mirrors retail (Sphere.cs::FindTimeOfCollision):
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// if (similar − cDist < 0) → return −1 × (cDist + similar) / distSq
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// else → return −1 × (similar − cDist) / distSq
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// The −1 negation converts from ACE's "closest-approach" parameterisation
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// back to a forward t ∈ (0,1] (positive = hit ahead of mover).
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float root = (similar - cDist < 0f) ? -(cDist + similar) : -(similar - cDist);
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// Normalise to [0, 1] scale
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t = root / distSq;
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// t ≤ 0: contact is behind / at the start (already handled by gap check).
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// t > 1: contact is beyond this movement step — miss.
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return t > 0f && t <= 1f;
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}
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// -----------------------------------------------------------------------
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// 9. land_on_sphere — FUN_00538f50
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// -----------------------------------------------------------------------
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