Class TGroupNode_1

Unit

Declaration

type TGroupNode_1 = class(TAbstractChildNode)

Description

This item has no description. Showing description inherited from TAbstractChildNode.

Abstract node type that indicates that the node may be used as a child of a grouping node, e.g. inside TAbstractGroupingNode.FdChildren.

Hierarchy

Overview

Methods

Public constructor Create(const AX3DName: string = ''; const ABaseUrl: String = ''); override;
Public procedure CreateNode; override;
Public class function ClassX3DType: String; override;
Public class function ForVRMLVersion(const Version: TX3DVersion): Boolean; override;

Description

Methods

Public constructor Create(const AX3DName: string = ''; const ABaseUrl: String = ''); override;

This item has no description. Showing description inherited from TX3DNode.Create.

Constructor. Initializes various properties:

  • Name, BaseUrl are initialized from given parameters.

  • The Fields, Events lists are filled in every descendant, to have all the fields/events defined by the specification.

  • DefaultContainerField, and other node-specific stuff, is filled in descendants. This is actually implemented in CreateNode, that is called at the end of this constructor.

Public procedure CreateNode; override;

Create node fields and events.

Public class function ClassX3DType: String; override;

This item has no description. Showing description inherited from TX3DNode.ClassX3DType.

Node type name in VRML/X3D, for this class. Normal VRML/X3D node classes should override this to return something non-empty, and then X3DType automatically will return the same value.

Empty for classes that don't have a hardcoded VRML/X3D node name, like a special TX3DUnknownNode. Such special classes should override then X3DType to return actual non-empty name there.

You usually should call X3DType. The only use of this method is that it works on classes (it's "class function"), without needing at actual instance.

Public class function ForVRMLVersion(const Version: TX3DVersion): Boolean; override;

This item has no description. Showing description inherited from TX3DNode.ForVRMLVersion.

Some nodes are present only in specific VRML/X3D version. This functions decides it.

For example some nodes can only work in VRML < 2.0, some others only in VRML >= 2.0. There are even some pairs of nodes: for example TConeNode_1 works with VRML < 2.0, TConeNode works with VRML >= 2.0.

NodesManager will use this.

Default implementation of this function returns always True. Generally, I don't try to set this too aggresively — in other words, for all cases when it's sensible, I allow nodes to be used in every VRML/X3D version, even when official specification doesn't. This means that when reading VRML 1.0 files actually a large part of VRML 2.0 is allowed too, and also while reading VRML 2.0 many constructs from VRML 1.0 (officially no longer present in VRML 2.0) are allowed too. I'm trying to support what I call a "sum of VRML 1.0 and 2.0".

In practice I only use this function when various VRML/X3D versions specify the same node name but

  • With different fields.

    For example Cone and Cylinder have slightly different fields, due to the fact that VRML 2.0 resigned from using TSFBitMask fields.

  • With different behavior.

    For example definitions of Sphere for VRML 1.0 and 2.0 are practically equal. However, the behavior from where to take texture and material info is different — in VRML 1.0 we take last Texture2, Material etc. nodes, while in VRML 2.0 we look in parent Shape's "appearance" field. So once again two different Sphere classes are needed.


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