78df1370b6
PhysicsObjUpdate.HandleAllCollisions — retail CPhysicsObj::handle_all_collisions (0x00514780, pc:282647): the velocity 'bleed on block' decision. fsf<=1 → reflect the into-surface component (v += -(v·n)(elasticity+1)·n) unless staying-on-walkable (retail's should_reflect guard, restoring the broader rule AD-25 suppressed); INELASTIC zeros instead; fsf>1 → v=0 entirely (the airborne-stuck fix). Bit round-trip owned by the Core resolve writeback (Slice 1), not re-encoded here. 7 conformance tests green. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
78 lines
4 KiB
C#
78 lines
4 KiB
C#
using System.Numerics;
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namespace AcDream.Core.Physics;
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/// <summary>
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/// Verbatim port of the collision-response tail of retail
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/// <c>CPhysicsObj::UpdateObjectInternal</c>: the velocity decision that
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/// <c>SetPositionInternal</c> (0x00515330) drives through
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/// <c>handle_all_collisions</c> (0x00514780, pc:282647). Kept as a pure function over a
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/// <see cref="PhysicsBody"/> + the resolve outcome so the whole decision is unit-testable
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/// in Core, independent of the App per-frame loop. The transition INTERNALS
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/// (<c>ResolveWithTransition</c> and below) are untouched.
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/// </summary>
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public static class PhysicsObjUpdate
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{
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/// <summary>
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/// retail <c>handle_all_collisions</c> (0x00514780). Reflects or zeros the body's
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/// <see cref="PhysicsBody.Velocity"/> (retail m_velocityVector) based on
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/// <see cref="PhysicsBody.FramesStationaryFall"/>:
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/// <list type="bullet">
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/// <item>fsf ≤ 1 → reflect the into-surface component
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/// (<c>v += -(v·n)(elasticity+1)·n</c>, pc:282712) when we should reflect and a
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/// collision normal is valid; an INELASTIC mover zeros instead (pc:282720).</item>
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/// <item>fsf > 1 → <c>v = 0</c> entirely (pc:282729) — the "bleed on block" that
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/// lets gravity resume so a blocked jump falls/glides off (fixes the #182
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/// airborne-stuck wedge).</item>
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/// </list>
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/// The Stationary* transient-bit round-trip (pc:282737-758) is owned by the Core resolve
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/// writeback (<c>PhysicsEngine.ResolveWithTransition</c>), not re-encoded here.
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/// </summary>
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/// <param name="body">The mover.</param>
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/// <param name="collisionNormalValid">Was a wall/creature collision normal recorded this resolve.</param>
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/// <param name="collisionNormal">Outward collision normal (points away from the surface).</param>
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/// <param name="prevContact">Whether the body had Contact BEFORE this resolve committed
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/// (retail arg3 — reserved for environment-collision reporting; unused today).</param>
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/// <param name="prevOnWalkable">Whether the body was OnWalkable before this resolve (retail arg4).</param>
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/// <param name="nowOnWalkable">Whether the body is OnWalkable after this resolve.</param>
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public static void HandleAllCollisions(
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PhysicsBody body,
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bool collisionNormalValid, Vector3 collisionNormal,
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bool prevContact, bool prevOnWalkable, bool nowOnWalkable)
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{
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// var_10_1 (pc:282653-282657): reflect UNLESS the mover stays on walkable ground
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// (and is not sledding). This restores retail's broader rule — the AD-25 airborne-only
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// suppression is retired: the landing-snap fragility it guarded is gone (landing state
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// is now owned by the SetPositionInternal-derived contact flags, not a Velocity.Z<=0
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// gate). A grounded corridor wall-slide keeps its tangential velocity (should_reflect
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// false), exactly as retail.
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bool sledding = body.State.HasFlag(PhysicsStateFlags.Sledding);
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bool shouldReflect = !(prevOnWalkable && nowOnWalkable && !sledding);
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if (body.FramesStationaryFall <= 1)
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{
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if (shouldReflect && collisionNormalValid)
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{
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if (body.State.HasFlag(PhysicsStateFlags.Inelastic))
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{
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body.Velocity = Vector3.Zero; // pc:282720-282722
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}
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else
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{
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float dot = Vector3.Dot(body.Velocity, collisionNormal);
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if (dot < 0f) // moving INTO the surface
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{
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float k = -(dot * (body.Elasticity + 1f)); // pc:282712
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body.Velocity += collisionNormal * k;
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}
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}
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}
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}
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else
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{
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body.Velocity = Vector3.Zero; // fsf>1 → THE BLEED (pc:282729)
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}
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_ = prevContact; // retail report_environment_collision(arg3) — weenie collision events, later.
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}
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}
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