TPrsStd_AISPresentation with wrong location / position

W. H.
Mon, 02/06/2023 - 10:56

Forums:

I try to read step file with opencascade, there are several ways to display the bodies in step file, but when I use TPrsStd_AISPresentation, the location of bodies will go wrong some times. AND when I use method prs->GetAIS()->SetLocalTransformation(loc) to change the location of the AIS Object of TPrsStd_AISPresentation, it will not work too.

Here is my sample codes

//! this will generate wrong location
for (XCAFPrs_DocumentExplorer aLeafIter(d->doc, XCAFPrs_DocumentExplorerFlags_OnlyLeafNodes);
    aLeafIter.More(); aLeafIter.Next())
{
    const XCAFPrs_DocumentNode& aDocNode = aLeafIter.Current();
    TopoDS_Shape aShape = XCAFDoc_ShapeTool::GetShape(aDocNode.RefLabel);
    if (!aShape.IsNull())
    {
        Handle(TPrsStd_AISPresentation) prs = TPrsStd_AISPresentation::Set(aDocNode.Label, XCAFPrs_Driver::GetID());
        prs->Display(true);
    }
}

//! this will generate right location
for (XCAFPrs_DocumentExplorer aLeafIter(d->doc, XCAFPrs_DocumentExplorerFlags_OnlyLeafNodes);
    aLeafIter.More(); aLeafIter.Next())
{
    const XCAFPrs_DocumentNode& aDocNode = aLeafIter.Current();
    TopoDS_Shape aShape = XCAFDoc_ShapeTool::GetShape(aDocNode.RefLabel);
    if (!aShape.IsNull())
    {
        aShape.Location(aDocNode.Location);
        Handle(AIS_Shape) ais = new AIS_Shape(aShape);
        //mCtx->Display(ais, true);
    }
}

I want to know why SetLocalTransformation Method does'work AND why the location was not right?

Does anyone can help, Thank You!

Attachments:

wrong location.png

right location.png

gkv311 n
Tue, 02/07/2023 - 12:41

Please use 'insert code' in editor or Markdown syntax to make shared code readable.

W. H.
Thu, 02/09/2023 - 07:09

sorry, I did't notice that

gkv311 n
Tue, 02/07/2023 - 12:44

Why would you want using TPrsStd_AISPresentation instead of more straightforward XCAFPrs_AISObject?

W. H.
Wed, 02/08/2023 - 05:52

gkv:
Thank you for your reply!
Because I want to store the AIS Objects to ocaf. Before I use TPrsStd_AISPresentation, I have to use a map to keep the relationship of Label and AIS Object. I think may be that's not the best practice, so I want to try TPrsStd_AISPresentation.

W. H.
Wed, 02/08/2023 - 05:53

gkv311 n
Fri, 02/10/2023 - 20:47

    const XCAFPrs_DocumentNode& aDocNode = aLeafIter.Current();
    TopoDS_Shape aShape = XCAFDoc_ShapeTool::GetShape(aDocNode.RefLabel);
    aShape.Location(aDocNode.Location);
    Handle(AIS_Shape) ais = new AIS_Shape(aShape);

The code above works as expected, because you pass shape location from XCAFPrs_DocumentExplorer tool. XCAFPrs_DocumentExplorer combines transformation of all parent nodes in XCAF tree and provides a final location that could be applied to aDocNode.RefLabel to locate shape in the world space.

    const XCAFPrs_DocumentNode& aDocNode = aLeafIter.Current();
    TopoDS_Shape aShape = XCAFDoc_ShapeTool::GetShape(aDocNode.RefLabel);
    if (!aShape.IsNull())
    {
        Handle(TPrsStd_AISPresentation) prs = TPrsStd_AISPresentation::Set(aDocNode.Label, XCAFPrs_Driver::GetID());
        prs->Display(true);

This code doesn't use location accumulated by XCAFPrs_DocumentExplorer tool. Instead, it takes aDocNode.Label (instead of aDocNode.RefLabel). These shape labels have no information about all parents nodes (in fact, shape label may be a child of several different parent nodes having different final location). So that displaying this presentation preserves only transformation of a child relative to a single parent, which is not what you are looking for.

I'm not familiar with a proper way for setting location to TPrsStd_AISPresentation (overriding XCAFPrs_Driver::Update() in a driver subclass?), but you need somehow passing this location information to interactive object (AIS_InteractiveContext::SetLocation()) or to shape.

W. H.
Sun, 02/12/2023 - 09:54

Thank you very much for your explain!
I will try your suggestion.