GLScene拾取

Question

在pick演示中，我一直使用GLSceneViewer1.Buffer.GetPickedObject( x，y)在GLViewerMouseDown事件中选择GLscene对象。我需要选择一个对象，改变颜色，用鼠标左键点击，再用鼠标左键点击取消选择，如果选择了另一个对象，它就被取消选择。似乎TGLSceneObject需要一个属性IsPicked : boolean才能实现这一点。如果有人知道不用修改GLScene就能做到这一点，那就太酷了。这是我写的代码，它可以工作，但不能工作。SetSelected( Selected，SelectedColor )只是改变所选对象的颜色。

procedure TForm32.GLSceneViewer1MouseDown( Sender : TObject; Button : TMouseButton; Shift : TShiftState; X, Y : Integer );
  var
    Selected : TGLSceneObject;
    AButton : TGLMouseButton;
  begin
    AButton := TGLMouseButton( Button );

    // if an object is picked...
    Selected := ( GLSceneViewer1.Buffer.GetPickedObject( x, y ) as TGLSceneObject );

      case AButton of
        mbLeft:
          begin
              if( Selected <> UnSelected ) then
                begin
                   if( Assigned( Selected ) ) then
                      begin
                        SetSelected( Selected, SelectedColor );
                        StatusBar1.Panels[0].Text := 'Selected';
                        UnSelected := Selected;
                      end
                   else
                    if( not Assigned( Selected ) ) then
                      begin
                        UnSelected.Material.FrontProperties.Emission.Color:= clrBlack;
                        UnSelected.Material.FrontProperties.Ambient.Color := clrGray20;
                        UnSelected.Material.FrontProperties.Diffuse.Color := clrGray80;
                        StatusBar1.Panels[0].Text := 'Unselected';
                        UnSelected := Selected;
                      end;
                end;
          end;
      end;
  end;

对我来说，这会更容易：

procedure TForm32.GLSceneViewer1MouseDown( Sender : TObject; Button : TMouseButton; Shift : TShiftState; X, Y : Integer );
  var
    Selected : TGLSceneObject;
  begin
    Selected := ( GLSceneViewer1.Buffer.GetPickedObject( x, y ) as TGLSceneObject );
      if( not Selected.IsPicked ) then
        SetSelected( Selected, SelectedColor )
      else
        SetSelected( Selected, UnSelectedColor );
   end;

Answer 1

经过一番讨论，我是否应该通过修改源代码来破坏我的GLScene库，这将需要分发源代码，这对我来说并不理想，我想出了以下代码来解决我的问题。答案似乎是维护一个我命名为CurrentSelection的TGLSceneObject buffer对象。

procedure TForm32.GLSceneViewer1MouseDown( Sender : TObject; Button : TMouseButton; Shift : TShiftState; X, Y : Integer );
  //CurrentSelection : TGLSceneObject; //TForm private declaration
  //Selected : TGLSceneObject; //TForm private declaration
  begin
    Selected := ( GLSceneViewer1.Buffer.GetPickedObject( x, y ) as TGLSceneObject );
      if( Selected <> nil ) then  //Avoid access violation error
        begin
          if( Assigned( CurrentSelection ) ) then //If CurrentSelection is not nil deselect it
            SetSelectedColor( CurrentSelection, UnSelectedColor );

          if( Selected = CurrentSelection ) then 
            begin 
              //has the same object been clicked then deselect it and clear the buffer object
              SetSelectedColor( Selected, UnSelectedColor );
              CurrentSelection := nil;
            end
          else
            begin 
              //if no object is selected select an object, set the color and assign the object to the buffer
              SetSelectedColor( Selected, SelectedColor );
              CurrentSelection := Selected;
            end;
        end;
  end;

设置TGLSceneObject的颜色

procedure TForm32.SetSelectedColor( Selected : TGLSceneObject; Color : TColorVector );
  begin
    Selected.Material.FrontProperties.Ambient.Color := Color;
    Selected.Material.FrontProperties.Diffuse.Color := Color;
    Selected.Material.FrontProperties.Emission.Color:= clrBlack;
  end;

上面的代码没有检查使用了哪个鼠标按钮，但我可以选择一个对象，取消选择该对象，当选择另一个对象时，它将取消选择当前对象。

我需要修改它以将取消选择的对象设置为其原始颜色/材质，但这应该是相对简单的。

干杯:)