Float precision loss far from origin: prefab cockpit rotation and Searchlight light offset

There are two places that round an absolute world position to a 32-bit float. Far from the origin the precision gets course, finally becoming a problem once the float step is 32m at 268,435 km jumping to 64m at 536,871 km, so the result is off by tens of meters. The float step doubles every power of 2. The proposed fixes resolve these issues and should make very large system entirely playable as long as mods that handle absolute positions use doubles as well.

1. Prefab spawn: cockpit rotation

Sandbox.Game.World.MyPrefabManager.SpawnPrefabInternalSetProperties

With SpawningOptions.RotateFirstCockpitTowardsDirection, a prefab containing a cockpit, remote control or flight block is placed tens of metres off, buried or floating. Prefabs without such a block are fine it seems.

Cause: the rotation matrix that turns the whole prefab about its cockpit so the cockpit faces the requested direction is built as a float Matrix from the pivot block's absolute world matrix.

Fix:

- Matrix matrix = Matrix.Identity;

+ MatrixD matrix = MatrixD.Identity;

- matrix = Matrix.Multiply(Matrix.Invert(m), Matrix.CreateWorld(myCubeBlock.WorldMatrix.Translation, spawnPrefabProperties.Forward, spawnPrefabProperties.Up));

+ matrix = MatrixD.Multiply(MatrixD.Invert(m), MatrixD.CreateWorld(m.Translation, spawnPrefabProperties.Forward, spawnPrefabProperties.Up));

2. Searchlight: light drawn away from its block

Sandbox.Game.EntityComponents.MyLightingLogic

The Searchlight's light is drawn metres to tens of metres from the block. Spotlights and interior lights are not affected.

Cause: MySearchlight.UpdateAfterSimulationParallel passes worldMatrix.Translation (a Vector3D) to MyLightingLogic.UpdateAfterSimulation(Vector3 lightPosition, MatrixD), whose parameter is a float Vector3. UpdateLightPosition(Vector3, MatrixD) then builds the light position from that rounded value.

Fix: change Vector3 to Vector3D in the two signatures, and the "no position" marker Vector3.PositiveInfinity to Vector3D.PositiveInfinity in its three uses.

- public void UpdateAfterSimulation(Vector3 lightPosition, MatrixD lightRotation)

+ public void UpdateAfterSimulation(Vector3D lightPosition, MatrixD lightRotation)

- UpdateAfterSimulation(Vector3.PositiveInfinity, MatrixD.Zero);

+ UpdateAfterSimulation(Vector3D.PositiveInfinity, MatrixD.Zero);

- UpdateLightPosition(Vector3.PositiveInfinity, MatrixD.Zero);

+ UpdateLightPosition(Vector3D.PositiveInfinity, MatrixD.Zero);

- public void UpdateLightPosition(Vector3 lightPosition, MatrixD lightRotation)

+ public void UpdateLightPosition(Vector3D lightPosition, MatrixD lightRotation)

- if (lightPosition == Vector3.PositiveInfinity)

+ if (lightPosition == Vector3D.PositiveInfinity)

I was able to test this using a pulsar plugin. The plugin applies the same two double-precision fixes as the report by patching the game from outside (it rotates prefabs about their cockpit in MatrixD, and sets the Searchlight’s light position from its exact world position), and everything else in it is support that a fix inside the game would not need: it re-implements the game’s pivot-block choice, computes all the new matrices before changing anything, falls back to the game’s own path or switches itself off if something throws, logs [LargeScalePrecisionFix] lines, and removes its patches on shutdown. I have provided the source just in case.

I've also attached some screenshots of before and after the fix was applied.

Please let me know if you require anything else.