Class TMFVec2f

Unit

VRMLFields

Declaration

type TMFVec2f = class(TVRMLSimpleMultField)

Description

Multiple values VRML field. Remember that such field may always have any number of items, including zero.

Note that we keep MF fields contents in TDyn*Array instances (RawItems in this class, also accessible as Items (with more concrete class) in descendants). This means that they are in compact form, easy for reading, or even for feeding the list into OpenGL. That's the main reason why I did not simply implement TVRMLSimpleMultField as a descendant of TVRMLSingleFieldsList: A long list of vertexes, MFVec3f, would be kept as a list of pointers to a lot of TSFVec3f instances. This would be quite memory-consuming, and very uncomfortable for access. On the contrary, current implementation keeps all these vertexes inside one TDynVector3SingleArray instance, that internally keeps all items in one continuos piece of memory.

Descendants implementors notes: to make new descendant:

• In CreateUndefined you have to initialize FItemClass and create RawItems. In destructor of this class, RawItems are freed, so don't worry about this.

• Override RawItemsAdd.

• If your ItemClass doesn't work 100% correctly when it's initialized by CreateUndefined, you may have to override CreateItemBeforeParse. Fortunately, VRML specification was careful to choose as multi-valued field types' only fields that can behave nicely when initialized by CreateUndefined (and in fact VRML 2.0 removed the "bad fields" entirely).

• Not strictly required, but usually it's comfortable to have a constructor that allows you to init default field value from some "array of TXxx".

Hierarchy

• TPersistent
• TNonRefCountedInterfacedPersistent
• TVRMLFileItem
• TVRMLFieldOrEvent
• TVRMLField
• TVRMLMultField
• TVRMLSimpleMultField
• TMFVec2f

Overview

Methods

	function RawItemToString(ItemNum: integer): string; override;
	function Items: TDynVector2SingleArray;
	procedure RawItemsAdd(Item: TVRMLSingleField); override;
	constructor Create(AParentNode: TVRMLFileItem; const AName: string; const InitialContent: array of TVector2Single);
	constructor CreateUndefined(AParentNode: TVRMLFileItem; const AName: string); override;
	function EqualsDefaultValue: boolean; override;
	function Equals(SecondValue: TVRMLField; const EqualityEpsilon: Double): boolean; override;
	procedure AssignLerp(const A: Double; Value1, Value2: TVRMLField); override;
	function CanAssignLerp: boolean; override;
	procedure Assign(Source: TPersistent); override;
	procedure AssignValue(Source: TVRMLField); override;
	procedure AssignDefaultValueFromValue; override;
	class function VRMLTypeName: string; override;

Properties

property ItemsSafe[Index: Integer]: TVector2Single read GetItemsSafe write SetItemsSafe;

Description

Methods

	function RawItemToString(ItemNum: integer): string; override;

	function Items: TDynVector2SingleArray;

	procedure RawItemsAdd(Item: TVRMLSingleField); override;

	constructor Create(AParentNode: TVRMLFileItem; const AName: string; const InitialContent: array of TVector2Single);

	constructor CreateUndefined(AParentNode: TVRMLFileItem; const AName: string); override;

	function EqualsDefaultValue: boolean; override;

	function Equals(SecondValue: TVRMLField; const EqualityEpsilon: Double): boolean; override;

	procedure AssignLerp(const A: Double; Value1, Value2: TVRMLField); override;

	function CanAssignLerp: boolean; override;

	procedure Assign(Source: TPersistent); override;

	procedure AssignValue(Source: TVRMLField); override;

	procedure AssignDefaultValueFromValue; override;

	class function VRMLTypeName: string; override;

Properties

	property ItemsSafe[Index: Integer]: TVector2Single read GetItemsSafe write SetItemsSafe;
Access Items[] checking for range errors. In case of errors, Get will return zero vector, Set will do nothing, and both will produce clear VRMLNonFatalError.