090b6d18dc
DrawAhead.Rotation delegates to Turned(pose, angle) so the turn is testable on a tilted pose, where the flat Duel poses make the quaternion product's off-axis terms vanish. Unverified at this commit. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
38 lines
1.9 KiB
C#
38 lines
1.9 KiB
C#
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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using CultMath;
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using static CultMath.math;
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// Where a presenter draws the latest sim state when the frame falls Lead sim seconds after the last step. Pure reads
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// of the simulation for presenters (never called by ServerShared): the sim owns every pose and no presenter stores
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// one, a previous state or a velocity of its own.
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public static class DrawAhead
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{
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public static float3 Position(Entity entity, float lead) =>
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entity.Position + float3(entity.Velocity.x, 0, entity.Velocity.y) * lead;
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// The ship's rotation turned about its own up axis by the rate its last step turned, for lead seconds.
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public static quaternion Rotation(Ship ship, float lead) => Turned(ship.Rotation, ship.TurnRate * lead);
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// q turned about its own up axis by the angle, in the sense Direction turns for a positive TurnRate.
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public static quaternion Turned(quaternion q, float angle)
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{
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var u = float3(q.x, q.y, q.z);
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var up = float3(0, 1, 0);
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up += 2 * (q.w * cross(u, up) + cross(u, cross(u, up)));
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var half = angle * .5f;
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var s = sin(half);
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var t = new quaternion(up.x * s, up.y * s, up.z * s, cos(half));
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// Hamilton product t * q: CultMath carries no quaternion product (a gap in CultMath, not filled here).
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return normalize(new quaternion(
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t.w * q.x + t.x * q.w + t.y * q.z - t.z * q.y,
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t.w * q.y - t.x * q.z + t.y * q.w + t.z * q.x,
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t.w * q.z + t.x * q.y - t.y * q.x + t.z * q.w,
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t.w * q.w - t.x * q.x - t.y * q.y - t.z * q.z));
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}
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// Zone time for a presenter that evaluates a sim function of time (FireControl.RoundAt).
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public static float Time(Zone zone, float lead) => zone.Time + lead;
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}
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