Spline

You can create lines and curves in Lumberyard Editor by using the Spline component,

A spline is a curve that connects two or more specific points. This is useful if you want to animate entities along a spline, such as a road or river.

Topics

• Spline Properties
• Working with Spline Components
• EBus Request Bus Interface

Spline Properties

The Spline component has the following properties.

By default, a Spline component has four vertices that are spaced evenly in a line. The vertex positions are stored in the local space of the entity.

Working with Spline Components

You can move the vertices in the local space of the entity along each axis. Each vertex has a planar, linear, and surface manipulator. Combined, these are called the translation manipulator. You can use the translation manipulator to move the vertices.

To change the vertex positions for a spline

1. Do one of the following:

   • In the viewport, double-click the spline.
   • In the Entity Inspector, choose Edit. For more information, see Editing Components in the Viewport.

2. Do one of the following:

• Select a vertex on the component and drag either the blue, green, or red arrow (linear manipulator) or the hollow blue, green, or red square (planar manipulator) to a position.
• Select a vertex on the component and drag the yellow point (surface manipulator) to move the vertex.

Note
The manipulators follow the grid snap setting that you can specify in Lumberyard Editor toolbar. For more information, see Using the Top Toolbar.

Note
The manipulators behave correctly if the entity is scaled, but the scaling must be uniform so that the x, y, and z values match (for example, 2.0, 2,0, 2.0). We recommend that you use uniform scaling for entities with a Spline component.

You can also select multiple vertices.

To select multiple vertices on a spline

• Hold Ctrl and select the vertices. Selected vertices appear yellow.
  Note
  Currently, you can’t click and draw a box around the vertices to select them.

You can also snap a vertex to another position on the terrain.

To snap a vertex to another position

1. Select a vertex.

2. Hold Shift+Ctrl and click another position on the terrain. The vertex snaps to that position.

You can also add vertices to the spline.

To add a vertex to a spline

1. Pause over a line and hold Ctrl. A preview appears where you can add the vertex.
   

2. Click to add the vertex to the spline.
   

You can also delete vertices from the spline.

To delete a vertex from the spline

1. Hold Alt and pause on a vertex. The vertex appears gray.
   

2. Click the vertex to delete it. You can also select a vertex and press Delete. Note
   Linear and Bézier splines must have a minimum of two vertices. Catmull-Rom splines must have a minimum of four vertices.
   

If you change the spline type, the component is updated to represent the new interpolation method.

Example Bézier

Example Catmull-Rom

Note
The first and last vertices of a Catmull-Rom spline are only control points. They don’t form part of the curve. A well-formed Catmull-Rom spline must have a minimum of four vertices. The spline doesn’t render if there are fewer than four vertices.

The following examples show how Catmull-Rom splines change when you adjust the Knot Parameterization property.

Example Knot Parameterization = 0

Example Knot Parameterization =1

Example Linear and Bézier Splines
The following examples are linear and Bézier splines with the same vertices but with open and closed loops.

EBus Request Bus Interface

Use the following request functions with the SplineComponentRequestBus EBus interface to communicate with other components of your game. The Spline component also uses VertexContainer functions. For more information, see Vertex Containers.

For more information about using the event bus (EBus) interface, see Working with the Event Bus (EBus) system.

Example
The following script uses the request bus interface.

local spline = SplineComponentRequestBus.Event.GetSpline(self.entityId);
 
  
-- GetNearestAddressPosition
local posSplineQueryResult = spline:GetNearestAddressPosition(Vector3(0, 0, 0));
  
posSplineQueryResult.splineAddress
posSplineQueryResult.splineAddress.segmentIndex
posSplineQueryResult.splineAddress.segmentFraction
posSplineQueryResult.distanceSq
  
-- GetNearestAddressRay
local raySplineQueryResult = spline:GetNearestAddressRay(Vector3(10, -1, 0), Vector3(0, -1, 0));
raySplineQueryResult.splineAddress.segmentIndex
raySplineQueryResult.splineAddress.segmentFraction
raySplineQueryResult.distanceSq
raySplineQueryResult.rayDistance
  
local splineAddressFromDistance = spline:GetAddressByDistance(3.0);
local splineAddressFromFraction = spline:GetAddressByFraction(0.75);
  
-- Test SplineAddress Constructor (1 param)
local splineAddress_1 = SplineAddress(2);
 
-- Test SplineAddress Constructor (2 params)
local splineAddress_2 = SplineAddress(1, 0);
  
spline:GetPosition(splineAddress_1)
spline:GetNormal(splineAddress_1)
spline:GetTangent(splineAddress_1)
spline:GetLength(splineAddress_1)
spline:GetSplineLength()
spline:GetSegmentLength(1)
spline:GetSegmentCount()
spline:GetSegmentGranularity()
  
local aabb = spline:GetAabb(Transform:CreateIdentity());
  
local closed = spline:IsClosed();
local firstVertex = spline.vertexContainer[1];
local lastVertex = spline.vertexContainer[spline.vertexContainer:Size()];
 
-- Attention: You can use the bus interface directly, but here (at the moment at least) indexing will start from 0, not 1 as is the norm in Lua. Instead, you should use the functions directly on the VertexContainer, listed below
SplineComponentRequestBus.Event.AddVertex(self.entityId, lastVertex + Vector3(1, 2, 3));
SplineComponentRequestBus.Event.UpdateVertex(self.entityId, 0, firstVertex + Vector3(1, 2, 3));
SplineComponentRequestBus.Event.InsertVertex(self.entityId, spline.vertexContainer:Size() - 1, lastVertex + Vector3(1, 2, 3));
SplineComponentRequestBus.Event.ClearVertices(self.entityId);
SplineComponentRequestBus.Event.RemoveVertex(self.entityId, spline.vertexContainer:Size() - 1);
  
-- Prefer these functions - indexing will start from 1
spline.vertexContainer:AddVertex(lastVertex + Vector3(1, 2, 3));
spline.vertexContainer:UpdateVertex(1, firstVertex + Vector3(1, 2, 3));
spline.vertexContainer:InsertVertex(spline.vertexContainer:Size(), lastVertex + Vector3(1, 2, 3));
spline.vertexContainer:ClearVertices();
spline.vertexContainer:RemoveVertex(spline.vertexContainer:Size());