How to calculate the bbox of brep entities (with BrepEntity.DataProps data)?

[XinJack]

Since I assume the BRep entity can be part of an actual element (GeometricElement3d), I only have access to BRepEntity.DataProps data. In this case, IModelConnection.elements.loadProps cannot be used.

[bbastings]

The local range of any BRep entities would have been accumulated to set the ElementAlignedBox3d (bbox) that is part of the element's placement, so you can just use that.

export interface Placement3dProps {
origin: XYZProps;
angles: YawPitchRollProps;
bbox?: LowAndHighXYZProps;
}

If that doesn't suffice you'll have to explain exactly what you are looking to do.

[XinJack]

The local range of any BRep entities would have been accumulated to set the ElementAlignedBox3d (bbox) that is part of the element's placement, so you can just use that.

export interface Placement3dProps { origin: XYZProps; angles: YawPitchRollProps; bbox?: LowAndHighXYZProps; }

If that doesn't suffice you'll have to explain exactly what you are looking to do.

Thank you for your prompt response. Let me clarify my use case in more detail. I have a GeometricElement3d composed of multiple geometries (e.g., BRep1 + LineString + BRep2). Currently, I need to query the bounding box (bbox) of only the BRep2 sub-geometry. (I have the BrepEntity.DataProps data of BRep2)

However, when using IModelConnection.elements.loadProps, it returns the bbox of the entire composite element instead of the specific BRep2 component, which doesn't meet my requirement.

[bbastings]

A geometry stream with multiple geometric entries that includes BReps should include local ranges too. If you are using GeometryStreamIterator or ElementGeometry.Iterator you can check to see if there is a valid local range when you encounter the BRep entry.

GeometryStreamIterator:

/** Holds current state information for [[GeometryStreamIterator]]. Each entry represents exactly one geometry primitive in the stream.
 * @public
 * @extensions
 */
export interface GeometryStreamIteratorEntry {
  /** A [[GeometryParams]] representing the appearance of the current geometric entry */
  readonly geomParams: GeometryParams;
  /** Placement transform, used for converting placement relative, local coordinate entries to world */
  readonly localToWorld?: Transform;
  /** Optional stored local range for the current geometric entry */
  readonly localRange?: Range3d; // <- Check this...
  /** Returns the geometric primitive represented by this entry. */
  readonly primitive: GeometryStreamPrimitive;
}

ElementGeometry.Iterator:

  /** Current state information for [[ElementGeometry.Iterator]] */
  export interface IteratorData {
    /** A [[GeometryParams]] representing the appearance of the current geometric entry */
    readonly geomParams: GeometryParams;
    /** Placement transform, used for converting placement relative, local coordinate entries to world */
    readonly localToWorld?: Transform;
    /** Optional stored local range for the current geometric entry */
    readonly localRange?: Range3d; // <- Check this...
    /** The current displayable opcode */
    readonly value: ElementGeometryDataEntry;
  }

You can't do much with BrepEntity.DataProps, it's just the binary transmit data for the brep. If you used IModelDb.elementGeometryRequest instead of IModelConnection.elements.loadProps to get the geometry, the "replaceBReps" option allows them to be returned as polyfaces.

[XinJack]

A geometry stream with multiple geometric entries that includes BReps should include local ranges too. If you are using GeometryStreamIterator or ElementGeometry.Iterator you can check to see if there is a valid local range when you encounter the BRep entry.

GeometryStreamIterator:

/** Holds current state information for [[GeometryStreamIterator]]. Each entry represents exactly one geometry primitive in the stream.
 * @public
 * @extensions
 */
export interface GeometryStreamIteratorEntry {
  /** A [[GeometryParams]] representing the appearance of the current geometric entry */
  readonly geomParams: GeometryParams;
  /** Placement transform, used for converting placement relative, local coordinate entries to world */
  readonly localToWorld?: Transform;
  /** Optional stored local range for the current geometric entry */
  readonly localRange?: Range3d; // <- Check this...
  /** Returns the geometric primitive represented by this entry. */
  readonly primitive: GeometryStreamPrimitive;
}

ElementGeometry.Iterator:

  /** Current state information for [[ElementGeometry.Iterator]] */
  export interface IteratorData {
    /** A [[GeometryParams]] representing the appearance of the current geometric entry */
    readonly geomParams: GeometryParams;
    /** Placement transform, used for converting placement relative, local coordinate entries to world */
    readonly localToWorld?: Transform;
    /** Optional stored local range for the current geometric entry */
    readonly localRange?: Range3d; // <- Check this...
    /** The current displayable opcode */
    readonly value: ElementGeometryDataEntry;
  }

You can't do much with BrepEntity.DataProps, it's just the binary transmit data for the brep. If you used IModelDb.elementGeometryRequest instead of IModelConnection.elements.loadProps to get the geometry, the "replaceBReps" option allows them to be returned as polyfaces.

Thanks a lot; I will try it out to see if it works.

[XinJack]

A geometry stream with multiple geometric entries that includes BReps should include local ranges too. If you are using GeometryStreamIterator or ElementGeometry.Iterator you can check to see if there is a valid local range when you encounter the BRep entry.

GeometryStreamIterator:

/** Holds current state information for [[GeometryStreamIterator]]. Each entry represents exactly one geometry primitive in the stream.
 * @public
 * @extensions
 */
export interface GeometryStreamIteratorEntry {
  /** A [[GeometryParams]] representing the appearance of the current geometric entry */
  readonly geomParams: GeometryParams;
  /** Placement transform, used for converting placement relative, local coordinate entries to world */
  readonly localToWorld?: Transform;
  /** Optional stored local range for the current geometric entry */
  readonly localRange?: Range3d; // <- Check this...
  /** Returns the geometric primitive represented by this entry. */
  readonly primitive: GeometryStreamPrimitive;
}

ElementGeometry.Iterator:

  /** Current state information for [[ElementGeometry.Iterator]] */
  export interface IteratorData {
    /** A [[GeometryParams]] representing the appearance of the current geometric entry */
    readonly geomParams: GeometryParams;
    /** Placement transform, used for converting placement relative, local coordinate entries to world */
    readonly localToWorld?: Transform;
    /** Optional stored local range for the current geometric entry */
    readonly localRange?: Range3d; // <- Check this...
    /** The current displayable opcode */
    readonly value: ElementGeometryDataEntry;
  }

You can't do much with BrepEntity.DataProps, it's just the binary transmit data for the brep. If you used IModelDb.elementGeometryRequest instead of IModelConnection.elements.loadProps to get the geometry, the "replaceBReps" option allows them to be returned as polyfaces.

I tried and it returns undefined. Looking into the source code, localRange is only set for SubRange.

itwinjs-core/core/common/src/geometry/ElementGeometry.ts

Line 655 in 92367f5

this.entry.localRange = ElementGeometry.toSubGraphicRange(value);

itwinjs-core/core/common/src/geometry/GeometryStream.ts

Line 698 in 92367f5

this.entry.localRange = Range3d.fromJSON(entry.subRange);

[bbastings]

Looking into the source code, localRange is only set for SubRange.

That is correct. It is common for sub ranges to be added to geometry streams with multiple geometric entries. Sub ranges are optional however and unfortunately the creator of your elements chose not to include them.

[XinJack]

That is correct. It is common for sub ranges to be added to geometry streams with multiple geometric entries. Sub ranges are optional however and unfortunately the creator of your elements chose not to include them.

In this case, do we consider providing APIs for BRep querying, like SolidUtil::GetEntityRange, ... in MicroStation?

[bbastings]

In this case, do we consider providing APIs for BRep querying, like SolidUtil::GetEntityRange, ... in MicroStation?

There are currently no plans to do so. You didn't say how you would use the entity range, but as mentioned previously you have the option to return BReps as Polyfaces using IModelDb.elementGeometryRequest/replaceBReps.

[XinJack]

There are currently no plans to do so. You didn't say how you would use the entity range, but as mentioned previously you have the option to return BReps as Polyfaces using IModelDb.elementGeometryRequest/replaceBReps.

Currently, I want to scale BRep geometries according to their bounding box (Which I think it's a common operation in 3D modeling). Returning BRep as polyfaces seems to be a workaround here; I will try it out.

[bbastings]

Which I think it's a common operation in 3D modeling

Not in my experience. You'd typically only scale the entire element about a point, center, or origin.

It isn't very common for solid modeling tools to accept an element with a mix/multiple geometries as these are generally created to represent some higher level component. Generic modification tools would typically only accept an element whose geometry is a single curve, surface, or solid.

[XinJack]

Thank you for sharing your insights! I will consider adjusting the existing workflow accordingly.