Draw wire between two invisible objects

[M.a.]

Hi,
I have several invisible object ( such as TGLsphere) as connection points and I want to pick these objects and draw wires ( such as wire example )
How can I do that?

[shine world]

To draw wires (lines) just Show object at runtime and change object material polygon mode with what you want (TGLPolygonMode = (pmFill, pmLines, pmPoints))

        OBJ.Material.Material.PolygonMode := <polygon_mode>;

[M.a.]

hi shine , I have 2 freeform such as electrical device , I defined 2 point by two sphere for connection point but these spheres are invisible , I want to connect line (as wire) between two free form connection point at runtime bye mouse. how detect the position of that sphere for add line node?

[shine world]

Actually there are two ways, that I know, to detect a picked object:

• Picked Object By Raycast
• GLSceneViewer.Buffer.GetPicketObject (use a mask on surfaces draw to detect object).

In below code I'm looking for TFreeForm object in pick search but you can change to other types.

procedure TGLSceneFrame.GLSceneViewerMouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
var
  PickedObject: TGLBaseSceneObject;

// TODO: To complete, seem inacurate and slow!!!
{$IFDEF EXPERIMENAL_RAY_CAST}
  function GetPickedObjectRayCast(const Root: TGLBaseSceneObject; X, Y: Integer): TGLBaseSceneObject;
  var
    T: Integer;
    Dist: Single;
    IPoint: TVector;
    INormal: TVector;
    RayStart: TVector;
    RayVector: TVector;
    HasRayCast: Boolean;
  begin
    Result := nil;
    SetVector(RayStart, GLSceneViewer.Camera.AbsolutePosition);
    SetVector(RayVector, GLSceneViewer.Buffer.ScreenToVector(AffineVectorMake(X, GLSceneViewer.Height - Y, 0)));
    NormalizeVector(RayVector);
    for T := 0 to Root.Count - 1 do
    begin
      if not (Root[T] is TGLFreeForm) then Continue;
      if Root[T].Visible then
      begin
        HasRayCast := Root[T].RayCastIntersect(RayStart, RayVector, @IPoint, @INormal);
        if HasRayCast and (VectorDotProduct(RayVector, INormal) < 0) then
        begin
          Dist := VectorLength(VectorSubtract(IPoint, RayStart));
          Result := Root[T];
          Exit;
        end;
      end;
    end;
  end;
{$ENDIF}

begin
  // stores mouse coordinates when a button went down
  FMDX := X;
  FMDY := Y;

  // checks if left mouse and control key pressed
  if Shift = [ssCtrl, ssLeft] then
  begin
    PickedObject := GLSceneViewer.Buffer.GetPickedObject(X, Y);
    if PickedObject is TGLFreeForm then
    begin
{$IFDEF EXPERIMENAL_RAY_CAST}
      // define selected object in the virtual machine manager
      FVMManager.PickedPart := TGLFreeForm(GetPickedObjectRayCast(VMManager.MachineFParts, X, Y));
{$ELSE}
      // define selected object in the virtual machine manager
      FVMManager.PickedPart := TGLFreeForm(PickedObject);
{$ENDIF}
    end
    else
      FVMManager.PickedPart := nil;
  end;

  // sets screen cursor to meet active operation
  if ssRight in Shift then
    Screen.Cursor := crOpacityPan
  else if (ssLeft in Shift) and not (ssCtrl in Shift) then
    Screen.Cursor := crOpacityOrbit;
end;

I don't know if this can work for you.
It required a visible object to detect if picked.

A little video about how works:
https://youtu.be/fmwr5SVt__Q