Nerfed/Nerfed.Runtime/Systems/LocalToWorldSystem.cs

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using MoonTools.ECS;
using Nerfed.Runtime.Components;
using Nerfed.Runtime.Util;
using System.Numerics;
// TODO:
// Explore if having a WorldTransform and LocalTransfom component each holding position, rotation, scale values and the matricies is useful.
// Often you need to either get or set these values.
// If so, we probably need a utility funciton to do so. Since changing these values means that we need to update all the related data + children as well.
// TODO:
// When modifying transform all the children need to be updated as well.
namespace Nerfed.Runtime.Systems
{
public class LocalToWorldSystem : MoonTools.ECS.System
{
private readonly bool useParallelFor = true; // When having a low amount of transforms or when in debug mode this might be slower.
private readonly Filter rootEntitiesFilter;
private readonly Filter entitiesWithoutLocalToWorldFilter;
private readonly Action<int> updateWorldTransform;
public LocalToWorldSystem(World world) : base(world)
{
rootEntitiesFilter = FilterBuilder.Include<LocalTransform>().Exclude<Child>().Build();
if (useParallelFor)
{
entitiesWithoutLocalToWorldFilter = FilterBuilder.Include<LocalTransform>().Exclude<LocalToWorld>().Build();
updateWorldTransform = UpdateWorldTransformByIndex;
}
}
public override void Update(TimeSpan delta)
{
if (rootEntitiesFilter.Empty)
{
return;
}
if (useParallelFor)
{
Profiler.BeginSample("ParallelFor.LocalToWorldCheck");
// This check is needed because some entities might not have a LocalToWorld component yet.
// Adding this during the loop will break.
foreach (Entity entity in entitiesWithoutLocalToWorldFilter.Entities) {
Set(entity, new LocalToWorld(Matrix4x4.Identity));
}
Profiler.EndSample();
Profiler.BeginSample("ParallelFor.LocalToWorldUpdate");
// This should only be used when the filter doesn't change by executing these functions!
// So no entity deletion or setting/removing of components used by the filters in this loop.
Parallel.For(0, rootEntitiesFilter.Count, updateWorldTransform);
Profiler.EndSample();
}
else
{
foreach (Entity entity in rootEntitiesFilter.Entities)
{
Profiler.BeginSample("UpdateWorldTransform");
UpdateWorldTransform(entity, Matrix4x4.Identity);
Profiler.EndSample();
}
}
}
private void UpdateWorldTransformByIndex(int entityFilterIndex)
{
Profiler.BeginSample("UpdateWorldTransformByIndex");
Entity entity = rootEntitiesFilter.NthEntity(entityFilterIndex);
UpdateWorldTransform(entity, Matrix4x4.Identity);
Profiler.EndSample();
}
private void UpdateWorldTransform(in Entity entity, Matrix4x4 localToWorldMatrix)
{
// TODO: Only update dirty transforms.
// If a parent is dirty all the children need to update their localToWorld matrix.
// How do we check if something is dirty? How do we know if a LocalTransform has been changed?
if (Has<LocalTransform>(entity))
{
LocalTransform localTransform = Get<LocalTransform>(entity);
localToWorldMatrix = Matrix4x4.Multiply(localToWorldMatrix, localTransform.TRS());
LocalToWorld localToWorld = new(localToWorldMatrix);
Set(entity, localToWorld);
}
ReverseSpanEnumerator<Entity> childEntities = World.InRelations<ChildParentRelation>(entity);
foreach (Entity childEntity in childEntities)
{
UpdateWorldTransform(childEntity, localToWorldMatrix);
}
}
}
}