Graphical Entity Behavior Concepts

A set of ODA PRC SDK entities with graphical content are derived from the OdPrcBaseWithGraphics class. This class encapsulates an instance of the OdPrcGraphics class to enhance the OdPrcReferencedBase class.

The OdPrcGraphics class has a set of bits that controls visibility, color, material and some other aspects of graphical entity behavior. This bit field contains 16 bits, therefore it can be represented with an OdUInt16 value. To operate on the current state of behavior bit field, OdPrcGraphics class provides two methods:

• behaviourBitField() — Retrieves the current value of the behavior bit field (as an OdUInt16).
• setBehaviourBitField() — Sets a new behavior bit field value. It accepts an OdUInt16 value as an input parameter.

Behavior parameter values are represented in the following table. Definitions of appropriate constants can be found in the /Prc/Include/PrcDefines.h file.

Flag Type	Identifier	Value	Description
Entity Show Flag	PRC_GRAPHICS_Show	0x0001	Determines whether the entity is shown.
	PRC_GRAPHICS_SonHeritShow	0x0002	Son inheritance flag.
	PRC_GRAPHICS_FatherHeritShow	0x0004	Parent inheritance flag.
Color/material Flag	PRC_GRAPHICS_SonHeritColor	0x0008	Determines son inheritance for color or material.
	PRC_GRAPHICS_FatherHeritColor	0x0010	Determines parent inheritance for color or material.
Layer Flag	PRC_GRAPHICS_SonHeritLayer	0x0020	Determines son inheritance for layers.
	PRC_GRAPHICS_FatherHeritLayer	0x0040	Determines parent inheritance for layers.
Transparency Flag	PRC_GRAPHICS_SonHeritTransparency	0x0080	Determines son inheritance for transparency.
	PRC_GRAPHICS_FatherHeritTransparency	0x0100	Determines parent inheritance for transparency.
Line Pattern Flag	PRC_GRAPHICS_SonHeritLinePattern	0x0200	Determines son inheritance for line patterns.
	PRC_GRAPHICS_FatherHeritLinePattern	0x0400	Determines parent inheritance for line patterns.
Line Width Flag	PRC_GRAPHICS_SonHeritLineWidth	0x0800	Determines son inheritance for line width.
	PRC_GRAPHICS_FatherHeritLineWidth	0x1000	Determines parent inheritance for line width.
Is Entity Removed Flag	PRC_GRAPHICS_Removed	0x2000	Determines whether the entity has been removed and does not appear in the tree.

Common Behavior Algorithm

All graphical entity behaviors are managed using a common algorithm. Any entity can accept its own behavior setting value or inherit it from a parent entity in the occurrence tree.

Assume that in the first case the entity behavior type is named kUseSon, and in the second case is named kUseParent. The third variant is kUseCurrent, which is the same as kUseParent.

Behavior settings are represented as a set of bits either for the entity (sonBits) or for its parent (fatherBits), therefore in general the algorithm of determining an entity behavior type consists of the following steps:

• If sonInheritBit is switched ON in sonBits
  • kUseSon type is applied.
• Else
  • If sonInheritBit is switched ON in fatherBits
    • kUseParent is applied.
  • Else
    • If fatherInheritBit is switched OFF in fatherBits
      • kUseSon is applied.
    • Else
      • kUseCurrent is applied.

Examples of Handling Graphical Entity Visibility

Suppose that there is a .prc entity tree:

• Product Occurrence
  • Part Definition
    • PolyBrepModel_1
    • PolyBrepModel_2
    • PolyBrepModel_3

The first three bits of the behavior bit field are responsible for resolving the visibility of each entity. Examples below show how visibility of each entity is resolved when these bits have different values.

Example 1

Entity			Parent Inherit	Son Inherit	Show Bit Value	Show Flags	Is Entity Shown
Product Occurrence			0	0	1	0x01
	Part Definition		0	0	1	0x01
		PolyBrepModel_1	0	0	1	0x01	Yes
		PolyBrepModel_2	0	0	1	0x01	Yes
		PolyBrepModel_3	0	0	1	0x01	Yes

All entities have the PRC_GRAPHICS_Show bit set, therefore they all will be shown.

Example 2

Entity			Parent Inherit	Son Inherit	Show Bit Value	Show Flags	Is Entity Shown
Product Occurrence			0	0	1	0x01
	Part Definition		0	0	0	0x00	Yes
		PolyBrepModel_1	0	0	1	0x01	Yes
		PolyBrepModel_2	0	0	0	0x00	No
		PolyBrepModel_3	0	0	1	0x01	Yes

All entities are shown, except PolyBrepModel_2. Notice that despite PRC_GRAPHICS_Show not being set for Part Definition, child entities are shown anyway.

Example 3

Entity			Parent Inherit	Son Inherit	Show Bit Value	Show Flags	Is Entity Shown
Product Occurrence			0 or 1	1 or 0	0	0x02 (or 0x04)
	Part Definition		0	0	0	0x00
		PolyBrepModel_1	0	0	1	0x01	No
		PolyBrepModel_2	0	0	0	0x00	No
		PolyBrepModel_3	0	0	1	0x01	No

No entity is visible. Product Occurrence has the PRC_GRAPHICS_Show bit not set, and this value is inherited by other child entities.

Example 4

Entity			Parent Inherit	Son Inherit	Show Bit Value	Show Flags	Is Entity Shown
Product Occurrence			0 or 1	1 or 0	1	0x03 (or 0x05)
	Part Definition		0	0	0	0x00
		PolyBrepModel_1	0	0	1	0x01	Yes
		PolyBrepModel_2	0	0	0	0x00	No for Adobe 9.1, Yes for Adobe 11
		PolyBrepModel_3	0	0	1	0x01	Yes

All entities will be shown, except PolyBrepModel_2. The PRC_GRAPHICS_Show bit value is inherited by all child entities, but the local show bit value also will be applied by the && operation.

Example 5

Entity			Parent Inherit	Son Inherit	Show Bit Value	Show Flags	Is Entity Shown
Product Occurrence			0 or 1	1 or 0	1	0x03 (or 0x05)
	Part Definition		1	0	0	0x04
		PolyBrepModel_1	0	0	1	0x01	Yes
		PolyBrepModel_2	0	0	0	0x00	No for Adobe 9.1, Yes for Adobe 11
		PolyBrepModel_3	0	0	1	0x01	Yes

All entities are shown, except PolyBrepModel_2. PRC_GRAPHICS_FatherHeritShow can not override anything, even itself.

Example 6

Entity			Parent Inherit	Son Inherit	Show Bit Value	Show Flags	Is Entity Shown
Product Occurrence			0 or 1	1 or 0	1	0x03 (or 0x05)
	Part Definition		0	1	0	0x02
		PolyBrepModel_1	0	0	1	0x01	No
		PolyBrepModel_2	0	0	0	0x00	No
		PolyBrepModel_3	0	0	1	0x01	No

No entity is visible because PRC_GRAPHICS_SonHeritShow overrides other settings.

Example 7

If a parent entity has the removed flag set (PRC_GRAPHICS_Removed bit is equal to 1), then no child entity is shown.

Example 8: Using OdPrcReference

If one of the child entities is linked by an OdPrcReference object somewhere higher in the hierarchy (for example in ProductOccurrence entity), the linked entity's bit will be replaced with OdPrcReference object bits.

For example, if an OdPrcReference object points to a PolyBrepModel_3 entity and has (PRC_GRAPHICS_SonHeritShow | PRC_GRAPHICS_Show == 3) bits, then PolyBrepModel_3 is shown:

Entity			Parent Inherit	Son Inherit	Show Bit Value	Show Flags	Is Entity Shown
Product Occurrence			0 or 1	1 or 0	1	0x03 (or 0x05)
	Part Definition		0	1	0	0x02
		PolyBrepModel_1	0	0	1	0x01	No
		PolyBrepModel_2	0	0	0	0x00	No
		PolyBrepModel_3	Any	Any	Any	Any value	Yes

Handling of OdPrcTessFace Entity Behavior

An OdPrc3dTess entity contains an array of OdPrcTessFace objects. Each OdPrcTessFace object has its own behavior field. This behavior field denotes graphics behavior for the entity in the tree that owns the face tessellation, except the situation when the face tessellation has no graphic attributes (method lineAttributes() returns an empty array).

For example, if OdPrcTessFace::behavior is set to PRC_GRAPHICS_SonHeritColor for all OdPrcTessFace objects in a file, all entities will be drawn in the color that OdPrcTessFace line attributes contain. But if OdPrcTessFace::behavior is set to the PRC_GRAPHICS_SonHeritShow bit without the PRC_GRAPHICS_Show bit, it does not disable entity visibility because the Show property bit is not filtered on this level.

See Also

Work with Markup Entities
Work with PRC Entities

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