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Generic GetMassData (#6291)

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* Generic GetMassData

Nothing fancy. Also made the class version use the struct.

* Slim method

* Fix test
This commit is contained in:
metalgearsloth
2025-11-10 18:30:24 +11:00
committed by GitHub
parent 3f19d25018
commit 015bf3318b
2 changed files with 33 additions and 10 deletions
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20
Robust.Shared/Physics/Shapes/Polygon.cs
View File

@@ -41,6 +41,8 @@ internal record struct Polygon : IPhysShape
}
public Polygon(PhysShapeAabb aabb) : this(aabb.LocalBounds) {}
public Polygon(PolygonShape polyShape)
{
Unsafe.SkipInit(out this);
@@ -52,6 +54,24 @@ internal record struct Polygon : IPhysShape
polyShape.Normals.AsSpan()[..VertexCount].CopyTo(_normals.AsSpan);
}
internal Polygon(SlimPolygon slim)
{
Unsafe.SkipInit(out this);
Radius = slim.Radius;
VertexCount = slim.VertexCount;
_vertices._00 = slim._vertices._00;
_vertices._01 = slim._vertices._01;
_vertices._02 = slim._vertices._02;
_vertices._03 = slim._vertices._03;
_normals._00 = slim._normals._00;
_normals._01 = slim._normals._01;
_normals._02 = slim._normals._02;
_normals._03 = slim._normals._03;
Centroid = slim.Centroid;
}
public Polygon(Box2 box)
{
Unsafe.SkipInit(out this);

23
Robust.Shared/Physics/Systems/FixtureSystem.Shapes.cs
View File

@@ -73,7 +73,7 @@ namespace Robust.Shared.Physics.Systems
}
}
public static MassData GetMassData(IPhysShape shape, float density)
public static MassData GetMassData<T>(T shape, float density) where T : IPhysShape
{
var data = new MassData();
@@ -82,7 +82,7 @@ namespace Robust.Shared.Physics.Systems
return data;
}
public static void GetMassData(IPhysShape shape, ref MassData data, float density)
public static void GetMassData<T>(T shape, ref MassData data, float density) where T : IPhysShape
{
// Box2D just calls fixture.GetMassData which just calls the shape method anyway soooo
// we can just cut out the middle-man
@@ -106,16 +106,17 @@ namespace Robust.Shared.Physics.Systems
data.I = data.Mass * (0.5f * circle.Radius * circle.Radius + Vector2.Dot(circle.Position, circle.Position));
break;
case PhysShapeAabb aabb:
var polygon = (PolygonShape) aabb;
var polygon = new Polygon(aabb);
GetMassData(polygon, ref data, density);
break;
case Polygon fastPoly:
GetMassData(new PolygonShape(fastPoly), ref data, density);
case PolygonShape fatPoly:
GetMassData(new Polygon(fatPoly), ref data, density);
break;
case SlimPolygon slim:
GetMassData(new PolygonShape(slim), ref data, density);
var slimPoly = new Polygon(slim);
GetMassData(slimPoly, ref data, density);
break;
case PolygonShape poly:
case Polygon poly:
// Polygon mass, centroid, and inertia.
// Let rho be the polygon density in mass per unit area.
// Then:
@@ -142,6 +143,7 @@ namespace Robust.Shared.Physics.Systems
var count = poly.VertexCount;
DebugTools.Assert(count >= 3);
DebugTools.Assert(poly._normals._00 != Vector2.Zero);
Vector2 center = new(0.0f, 0.0f);
float area = 0.0f;
@@ -149,15 +151,16 @@ namespace Robust.Shared.Physics.Systems
// Get a reference point for forming triangles.
// Use the first vertex to reduce round-off errors.
var s = poly.Vertices[0];
var s = poly._vertices._00;
var polySpan = poly._vertices.AsSpan;
const float k_inv3 = 1.0f / 3.0f;
for (var i = 0; i < count; ++i)
{
// Triangle vertices.
var e1 = poly.Vertices[i] - s;
var e2 = i + 1 < count ? poly.Vertices[i+1] - s : poly.Vertices[0] - s;
var e1 = polySpan[i] - s;
var e2 = i + 1 < count ? polySpan[i+1] - s : polySpan[0] - s;
float D = Vector2Helpers.Cross(e1, e2);