Detailed Description
When a Mesh object or modifier (such as Editable Mesh, Edit Mesh, or Mesh Select) handles viewport subobject selection, the flow is basically as follows from Editable Mesh.
- EditTriObject::HitTest is called with window information.
- It passes the hit region description to
Mesh::SubObjectHitTest
-
Mesh::SubObjectHitTest culls some subobjects (say, because
they're backfacing), and creates hits for others that are within
the hit region.
- EditTriObject::SelectSubComponent is called with the list of
hits, and
constructs the appropriate BitArray selection.
The problem was that in cases of Window selection, you want to only select an element or polygon if all the faces of that element or polygon were in the selection region. But since some of these faces could have been culled, they might not have hit records even if they're within the correct region. This would mean, for instance, that a window selection of an entire Sphere would fail to get select its single element, because all the backfaces would not
have been selected.
So in order to do this correctly, we need the face culling information. This information is stored and applied in the new MeshSelectionConverter interface, which is part of class Mesh.
This sort of culling and subobject level translation is not only relevant for Polygon and Element selections, but also for "By Vertex" selections of edges, faces, polygons, or elements.
Examples of the use of this interface are available in maxsdk/SAMPLES/mesh/editablemesh/triobjed.cpp, and in meshsel.cpp and editmesh.cpp in maxsdk/SAMPLES/modifiers..
Owner: class Mesh
InterfaceID: MESHSELECTCONVERT_INTERFACE
- Flags:
- We have the usual three methods for setting, clearing, and
getting flags: void SetFlag (DWORD f, bool value=true) void
ClearFlag(DWORD
f) bool GetFlag (DWORD f)
We currently only have one flag influencing subobject selection conversion: MESH_SELCONV_REQUIRE_ALL
If set, it implies that, for instance, an element is only selected if all of its (non-culled) faces are selected. If cleared, an element is selected if any of its faces are selected.
#include <mnmesh.h>
Public Member Functions |
|
| DllExport void | FaceToElement (MNMesh &mesh, BitArray &faceSel, BitArray &elementSel) |
| Converts a face selection to an element
selection. |
|
| DllExport void | EdgeToBorder (MNMesh &mesh, BitArray &edgeSel, BitArray &borderSel) |
| DllExport void | VertexToEdge (MNMesh &mesh, BitArray &vertexSel, BitArray &edgeSel) |
| Converts a vertex selection to a "By Vertex"
edge selection. |
|
| DllExport void | VertexToFace (MNMesh &mesh, BitArray &vertexSel, BitArray &faceSel) |
Member Function Documentation
Converts a face selection to an element selection.
This method can only produce accurate results with culling if we
are certain that the face selection corresponds to the results of
the last call to
the owner Mesh's SubObjectHitTest method. (To turn off culling, use
GetCull ().ClearAll(). Culling is not relevant if the
MESH_SELCONV_REQUIRE_ALL flag
is turned off.)
Converts a vertex selection to a "By Vertex" edge selection.
This method can only produce accurate results with culling if we
are certain that the vertex selection corresponds to the results of
the last call
to the owner Mesh's SubObjectHitTest method. (To turn off culling,
use GetCull ().ClearAll(). Culling is not relevant if the
MESH_SELCONV_REQUIRE_ALL flag
is turned off.)
