# Reference on Topology/Tessellation

Creates and accesses entities that reference topological entities and that specify globally-defined attributes.

> 2.0

Entity type is `kA3DTypeMiscReferenceOnTopology`.

Referenced topological entities are retrieved by indexes which are meaningful in the context of their parent element.

For a `A3DTopoConnex`, it needs:

- the `A3DTopoConnex`index on the current `A3DTopoBrepData`.

For a `A3DTopoShell`, it needs:

-     A3DUns32uiShellIndex=0;
      forallpConnexonA3DTopoBrepData
      {
      forallpShellonpConnex
      {
      ifpShelliswanted
      returnuiShellIndex;
      uiShellIndex++;
      }
      }

For a `A3DTopoFace`, it needs:

-     A3DUns32uiFaceIndex=0;
      forallpConnexonA3DTopoBrepData
      {
      forallpShellonpConnex
      {
      forallpFaceonpShell
      {
      ifpFaceiswanted
      returnuiFaceIndex;
      uiFaceIndex++;
      }
      }
      }

For a `A3DTopoEdge`or `A3DTopoCoEdge`, it needs:

- the `A3DTopoFace`index on the current `A3DTopoBrepData`(see index need for `A3DTopoFace`reference).
- the `A3DTopoLoop`index on the current `A3DTopoFace`.
- the `A3DTopoCoEdge`index on the current `A3DTopoLoop`.

For a `A3DTopoVertex`, it needs:

- the `A3DTopoFace`index on the current `A3DTopoBrepData`(see index need for `A3DTopoFace`reference).
- the `A3DTopoLoop`index on the current `A3DTopoFace`.
- the `A3DTopoCoEdge`index on the current `A3DTopoLoop`.
- the `A3DTopoVertex`index on the current `A3DTopoEdge`. Is set to 0 for the start vertex, and 1 for the end vertex.

Parameters

> pData: The `A3DMiscReferenceOnTessData`instance to create reference from

> ppReferenceOnTess: A pointer to the resulting `A3DMiscReferenceOnTess`entity

Returns

> `A3D_SUCCESS`on success, or an error code on failure

Structures

- `A3DMiscReferenceOnTopologyData`
- `A3DMiscReferenceOnTessData`

Functions

- `A3DMiscReferenceOnTopologyGet()`
- `A3DMiscReferenceOnTessGet()`
- `A3DMiscReferenceOnTessCreate()`
- `A3DMiscReferenceOnTopologyCreate()`

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