Transforms

For representing a hierarchy of objects in 3D space.

Behaviour

Entities with the IsTransform tag will have a LocalToWorld component calculated using data from these components, relative to the parent:

• Position
• Rotation
• Scale
• Anchor
• Pivot

Modifying these components wont update the LocalToWorld component immediately, requiring a system to do so with a TransformUpdate message.

Axis convention

This is only relevant for rotations when working with them manually:

• X axis is right (pitch)
• Y axis is up (yaw)
• Z axis is forward (roll)

Anchoring to corners

The Anchor component is able to describe both relative and absolute values. The example below makes the child transform have a 10 pixel border inside the parent:

Transform parent = new(world);
parent.LocalScale = new(100, 100, 0);
parent.LocalPosition = new(50, 50, 0);

Transform child = new(world);
child.Anchor = new(10, 10, 0, 10, 10, 0, Anchor.Relativeness.X | Anchor.Relativeness.Y);

//after simulating, child will be at position (60, 60) with size (80, 80)

Reading world state

Accessing world position, rotation or scale is can be done through properties of a transform entity:

Transform a = ...
Vector3 position = a.WorldPosition;
Quaternion rotation = a.WorldRotation;
Vector3 scale = a.WorldScale;

And optionally, can be accessed directly through components. However, accessing the world rotation is not possible through the LocalToWorld component and must be done through WorldRotation:

uint a = ...
LocalToWorld ltw = world.GetComponent<LocalToWorld>(a);
Vector3 position = ltw.Position;
Vector3 scale = ltw.Scale;
Quaternion rotation = world.GetComponent<WorldRotation>(a).value;