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How to Set Different Colors for Local Highlight Elements

Visualization and 3D ViewerMon, 02/17/2025 - 03:014 replies

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QuestionAuthor

Content:

I am working with OCCT in C# and trying to set different colors for edges and faces when using SetHighlightStyle(LocalDynamic). Below is the Prs3d_Drawer setup I am using:

var drawer = new Prs3d_Drawer();
drawer.SetZLayer(-2);
drawer.SetupOwnDefaults();
drawer.SetDisplayMode(1);
drawer.SetColor(Color.Yellow.To_quantity_color());

var line_aspect = new Prs3d_LineAspect(Color.Red.To_quantity_color(), Aspect_TypeOfLine.SOLID, local_hovered.Edge.Thickness);
drawer.SetWireAspect(line_aspect);
drawer.SetFaceBoundaryAspect(line_aspect);
drawer.SetUnFreeBoundaryAspect(line_aspect);

var shading_aspect = new Prs3d_ShadingAspect();
shading_aspect.SetColor(Color.Green.To_quantity_color());
shading_aspect.SetTransparency(0);
shading_aspect.Aspect().SetPolygonOffsets((int)Aspect_PolygonOffsetMode.Fill, 0.99f, 0.0f);
drawer.SetShadingAspect(shading_aspect);

return drawer;

Observations:

  1. When setting
var line_aspect = new Prs3d_LineAspect(Color.Red.To_quantity_color(), Aspect_TypeOfLine.SOLID, local_hovered.Edge.Thickness);
  • The thickness of the edge is correctly applied.
  • However, the edge color does not change to red.
  1. When setting
var shading_aspect = new Prs3d_ShadingAspect();
shading_aspect.SetColor(Color.Green.To_quantity_color());
  • The face color does not change to green as expected.

Question:

Is there a way to display different colors for individual local elements (edges and faces) when using LocalDynamic highlight mode? How can I properly set different colors for edges and faces on hover?

Any insights or alternative methods would be appreciated.

Discussion

4 archived replies

Posts are displayed in their archived order.

01Commenter-1

Some image may help understand your question better.

It is possible to show different colors for edges than for faces, for default or hilight or selection drawing (using AIS_InteractiveContext is quite easy):

myAISContext()->DefaultDrawer()->SetFaceBoundaryDraw(Standard_True);
myAISContext()->DefaultDrawer()->SetFaceBoundaryAspect(new Prs3d_LineAspect(Quantity_NOC_BLACK, Aspect_TOL_SOLID, 1.0));

myAISContext()->HighlightStyle(theType)->ShadingAspect()->SetColor(theColor);
myAISContext()->HighlightStyle(theType)->SetFaceBoundaryDraw(Standard_True);
myAISContext()->HighlightStyle(theType)->FaceBoundaryAspect()->SetColor(theColor);

Hope it helps.

02Author

I have modified the drawer settings based on the comment that viewer.Graphic.Occt is an AIS_InteractiveContext.

Here is my updated code:

viewer.Graphic.Occt.DefaultDrawer().SetFaceBoundaryDraw(true);
var line_aspect = new Prs3d_LineAspect(Color.White.To_quantity_color(), Aspect_TypeOfLine.SOLID, 3.0);
viewer.Graphic.Occt.DefaultDrawer().SetFaceBoundaryAspect(line_aspect);

viewer.Graphic.Occt.HighlightStyle(Aspect_TOH_Type.Dynamic).ShadingAspect().SetColor(Color.Blue.To_quantity_color());
viewer.Graphic.Occt.HighlightStyle(Aspect_TOH_Type.Dynamic).SetFaceBoundaryDraw(true);
viewer.Graphic.Occt.HighlightStyle(Aspect_TOH_Type.Dynamic).FaceBoundaryAspect().SetColor(Color.Green.To_quantity_color());

Expected Behavior:

When I run the program:

  • Faces appear yellow.
  • Edges appear green.

I expected that when hovering the mouse in Edge or Face selection mode:

  • Edge selection mode → Edges should appear green.
  • Face selection mode → Faces should appear blue.

Issue:

However, this is not happening as expected. The DisplayMode of AIS_InteractiveContext is set to 1.

Did I miss something or make a mistake in my implementation? Any guidance would be appreciated!

Additional Screenshots:

  • 1.PNG → The default box rendering.
  • 2.PNG → When hovering the mouse in Edge selection mode.
  • 3.PNG → When hovering the mouse in Face selection mode.
03Commenter-2

I am working with OCCT in C# and trying to set different colors for edges and faces when using SetHighlightStyle(LocalDynamic)

AIS handles highlighting in a special way - by default, it doesn't (re)compute presentation, but modulates/overrides its properties like color. The behavior is managed by class Graphic3d_PresentationAttributes, which is the base of Prs3d_Drawer. Other properties of subclass Prs3d_Drawer are ignored when highlighting entire AIS_Shape, but some of them could take effect within local selection of subshapes (but color will be overridden anyway).

You would need customizing AIS_Shape to achieve highlighting of lines and triangles having different color (and/or probably improving OCCT itself).

There is trick, though. You may assign material for highlighting triangles Prs3d_Drawer::SetBasicFillAreaAspect() and color Prs3d_Drawer::SetColor() which will affect lines:

pload MODELING VISUALIZATION
box b 2 0 0 1 2 3
psphere s 1
vinit View1
vdisplay -dispMode 1 b s
vfit
vaspects b s -faceBoundaries 1 -faceBoundaryColor RED
vselprops dynHighlight -dispMode 1 -color BLUE -material PLASTIC
# now lines and triangles are highlighted in BLUE
vselprops dynHighlight -dispMode 1 -color GREEN
# now lines highlighted in GREEN and triangles in BLUE

Archived image: box_highlight

This wouldn't affect line thickness though.

04Author

Thank you for the detailed explanation.

Your insights on AIS highlighting behavior and possible customization approaches were really helpful.