IN THIS ARTICLE
Vertex Containers
Vertex Containers
VertexContainer is a concrete type and an interface that is used by several Lumberyard component buses. It is implemented directly by the Polygon Prism Shape component and the Spline component and used indirectly by the Navigation Area component.
Vertex Container Interface
A vertex container provides the ability to access, modify, add, and remove vertices. A vertex container has several interfaces that build upon one another.
These include the following interfaces:
Contents
FixedVertices Interface
The simplest interface is FixedVertices. FixedVertices supports GetVertex and UpdateVertex functions for vertices in a container and a Size function that returns the number of vertices in the container.
Because the number of vertices is fixed, vertices cannot be added or removed. You can implement this interface with an array or AZStd::fixed_vector.
VariableVertices Interface
The VariableVertices interface supports all the functionality of FixedVertices, but also provides AddVertex, InsertVertex, and RemoveVertex functions. VariableVertices also provides a utility function called Empty that checks whether a container has any elements or is empty.
To implement the VariableVertices interface, you can use either an AZStd::vector or a VertexContainer.
VertexContainerInterface
The VertexContainerInterface provides an interface to all functionality provided by the previous two interfaces and the VertexContainer type. For convenience, the VertexContainerInterface also provides SetVertices and ClearVertices functions that can update all vertices or remove all vertices in one operation. The SetVertices function takes a vertices parameter that contains a list of all vertices to be stored.
Note
A VertexContainer owns the vertices to which it has access; they are not stored elsewhere (a VertexContainer is not a view).
As mentioned, the VertexContainerInterface is implemented by the Spline component and Polygon Prism component EBuses. The Navigation Area component also uses the interface through its dependence on the Polygon Prism Shape component. Each of these components uses the VertexContainer type internally to manage its vertices.
For more information about the interfaces in the VertexContainerInterface, see the code and code comments in the lumberyard_version\dev\Code\Framework\AzCore\AzCore\Math\VertexContainerInterface.h file.
For more information about the VertexContainer type, see the code and code comments in the lumberyard_version\dev\Code\Framework\AzCore\AzCore\Math\VertexContainer.h file.
Note
The VertexContainer can store Vector2 or Vector3 types. The vector type is determined at compile time when the type is created. This is useful for certain components that do not allow points to be modified on the Z (vertical) axis and treat points just in two dimensions. The Polygon Prism component uses the Vector2 type.
EBus Request Bus Interface Example
The following is an example of a Lua script that uses the RequestBus interface.
local firstVertex = <type_with_vertex_container>.vertexContainer[1];
local lastVertex = <type_with_vertex_container>.vertexContainer[spline.vertexContainer:size()];
...RequestBus.Event.AddVertex(self.entityId, lastVertex + Vector3(1, 2, 3));
...RequestBus.Event.UpdateVertex(self.entityId, 0, firstVertex + Vector3(1, 2, 3));
...RequestBus.Event.InsertVertex(self.entityId, spline.vertexContainer:size() - 1, lastVertex + Vector3(1, 2, 3));
...RequestBus.Event.ClearVertices(self.entityId);
...RequestBus.Event.RemoveVertex(self.entityId, spline.vertexContainer:size() - 1);
-- Note: In Lua, use the member functions of VertexContainer, which start indexing from 1
.vertexContainer:AddVertex(lastVertex + Vector3(1, 2, 3));
.vertexContainer:UpdateVertex(1, firstVertex + Vector3(1, 2, 3));
.vertexContainer:InsertVertex(spline.vertexContainer:size(), lastVertex + Vector3(1, 2, 3));
.vertexContainer:ClearVertices();
.vertexContainer:RemoveVertex(spline.vertexContainer:size());