Lesson 6 – Introduction To 3DORBIT



You have seen that you can use the View command to quickly change viewing directions for standard views.

  • the 3dorbit command lets you dynamically view your 3D models from any direction.
  • you will probably use 3dorbit often if you regularly work in 3D.

The 3dorbit command is readily accessible from the usual menus (pulldown and standard toolbar)

  • but 3dorbit can also be invoked from a right-click shortcut when you are using Zoom or Pan in the realtime mode.
  • many of the options shown below for this shortcut are unavailable when the current shade mode is 2D Wireframe.
  • the same shortcut is available when 3dorbit is running and it includes many other related options in one convenient location.

When you invoke 3dorbit you will see an arcball image (with a circle at each quadrant) displayed in the center of the active viewport.

  • you can left-click and drag inside the arcball to dynamically change your viewpoint and orientation relative to your 3D model.

Your model is NOT moving (you are moving) when you use 3dorbit but it helps to imagine that the model is moving & you are stationary.

  • imagine that the model is attached to the arcball so if you revolve the arcball you will see the model from another viewpoint.
  • this arcball is like your mouse ball because it can swivel about any axis (turn your mouse upside down to see it in action!)

When you left-click and drag inside the arcball you can freely change the orientation of your model on-screen.

  • you may not understand it now but you should be comfortable with this interface after only a few minutes of practice.

If you left-click and drag outside the arcball it is like revolving a camera about the axis of the camera lens (roll).

  • you are essentially reducing the degrees of freedom for the arcball such that it can ONLY revolve about one axis.
  • this axis is perpendicular to the screen.

If you left-click in one of the smaller circles before dragging you can revolve the arcball about either a vertical or horizontal axis.

  • left-click first inside either the left or right side circles to restrict rotation about the vertical axis.
  • left-click first inside either the top or bottom circles to restrict rotation about a horizontal axis.

Visual Aids

The Compass is a collection of three dotted circles (same diameter as the arcball) that are perpendicular to the X, Y and Z axes.

  • you can toggle the Compass On or Off while 3dorbit is running and it will remain On or Off even when you exit 3dorbit.
  • you might find it helpful to use this aid when you are first learning how to use 3dorbit (but it will probably get in your way later on).

You can turn the Grid on to see the location of the XY plane (i.e. the construction plane for 2D objects) for the current UCS.

  • the grid is displayed over the current LIMITS (this setting can also be changed using the GRID button on the status bar).

The UCS Icon visual aid toggles the UCS icon On or Off.

  • you can also pick View + Display + UCS Icon + On in the pulldown menu.

Projection

The default mode for projection is Parallel, which projects the object image along a parallel path (parallel to the viewing direction).

  • there is no distortion of objects for this mode of projection.

If you want models to appear the way your eye (or a camera lens) would actually see them you can change projection to Perspective.

There are limitations when projection is Perspective.

  • for example, you CANNOT pick points on-screen for editing and you CANNOT use the Zoom or Pan commands in this mode.
  • you can, however, select Zoom or Pan from the right-clickshortcut (this invokes 3dzoom & 3dpan commands instead)

  • these points can be influenced by how you use 3dorbit and other display commands but the results may not be what you want.

The distortion effects for Perspective projection depend on the distance between the camera and target points.

  • you may have to use the Camera command to explicitly specify 3D points for the camera and target to achieve the best effect.
  • If you want to view models from the inside you must position the camera point inside the model
  • and change projection to Perspective if you want to use Hide (or use Shademode and select Hidden or Shaded modes).
  • otherwise, the outer surfaces of the model will obscure details inside the model.

Adjust Distance

You can dynamically move the camera closer to (or further away from) the target to change the distance between them.

One way to invoke 3ddistance is to use the right-click shortcut menu when 3dorbit is running.

Drag up or down to make the distance shorter or longer (this is like using the realtime option of Zoom).

– your cursor also changes form during this operation.

When projection is Parallel the results on-screen are similar to using the realtime option of Zoom

  • but when projection is Perspective you will notice more distortion as you decrease the distance.

Using 3dzoom (Zoom on the shortcut above) when projection is Perspective is like changing the lens length on a camera

  • you can simulate wide angle or telephoto lens effects.

Continuous Orbit

The Continuous Orbit feature lets you watch your model revolve continuously about any axis at variable speeds.

  • this is a practical tool for presenting your 3D models to others.

One way to invoke 3dcorbit (“C “is for Continuous) is to use theright-click shortcut menu when 3dorbit is running.

  • you control the direction of spin by the direction that you dragand the speed by how quickly you drag.

Swivel Camera

Swivel Camera is like turning your head to look elsewhere (changes your target point without changing the camera point).

  • drag your cursor to dynamically look in other viewing directions.

One way to invoke 3dswivel is to use the right-click shortcut menu when 3dorbit is running.

Clipping Planes

A clipping plane is an invisible plane and objects (or parts of objects) beyond this plane will not be displayed.

  • these planes will move dynamically as you change your view.

There are front & back clipping planes which can be turned On or

Off independently & you can change the location of these planes.

  • so you can hide objects in front of the front clipping plane or behind the back clipping plane as desired.
  • for example, in the model illustrated below you could isolate the middle set of table of chairs using appropriate clipping planes.

One way to invoke 3dclip is to use the right-click shortcut menu when 3dorbit is running.

The Adjust Clipping Planes window is displayed and you can drag the front & black clipping planes to the desired locations.

  • you should close this window when the planes are adjusted.

You must select one of the first three buttons at the top of this window to determine which plane is moved when you drag.

  • with Adjust Front Clipping selected you drag the front plane.
  • with Adjust Back Clipping selected you drag the back plane.
  • with Create Slice selected you drag both planes as a slice.

The front & back clipping planes can be turned On or Off by picking one of the last two buttons in this window.

  • they can also be toggled On or Off from the shortcut menu shown at the top of this page.
  • a check mark appears in the shortcut beside the appropriate clipping plane if that clipping plane is On.

3D Orbit Toolbar

So far in this section you have seen how to access various features and commands using the right-click shortcut menus.

  • this is perhaps the easiest way to invoke the desired tool and you will normally save time if you use this approach.

When you select Pan and Zoom from this shortcut you are actually using 3dpan and 3dzoom

  • this lets you use a similar interface as for Zoom & Pan in realtime mode when projection is parallel.

Many of the options in the More section of this shortcut are commands (that can be invoked even if 3dorbit is not running).

  • you will not find all of these commands in pulldown menus but there are buttons for them in the 3D Orbit toolbar.
  • there is even a drop-down list to select standard views when 3dorbit is running.

You should consider having the 3D Orbit toolbar displayed on-screen if you work regularly in 3D.

PRACTICE USING 3DORBIT

»1) Close the drawing from the previous exercise if it is open.

»2) Open the T302_4.dwg drawing in your personal folder.

»3) Pick View + 3D Orbit.

4) Right-click in the drawing area to invoke a shortcut and select Zoom. Drag downward so the 3D model is smaller than the arcball circle was when 3dorbit was runnning. Do not exit Zoom (yet).

You can easily toggle back and forth between 3dorbit and Pan or Zoom by using this right-click shortcut menu.

  • in the next step you will switch back to 3dorbit mode.

5) Right-click in the drawing area to invoke a shortcut menu and select Orbit.

6) Press <Enter> to exit 3dorbit.

The right-click shortcut Reset View option restores the view to what it was before you began the current 3dorbit command.

  • you will use this feature to come back to the view illustrated above after practicing various 3dorbit features.
  • this is why it is important to complete the 3dorbit command now (otherwise you will have to repeat steps 3 to 6).

7) Right-click in the drawing area to invoke a shortcut and select Repeat 3D Orbit.

8)Left-click near P1 and hold the mouse button down. Drag your cursor toward P2 & release the button. Try dragging with other points inside the arcball but remain in the same 3dorbit command.

If you do not see why the view changes the way it does you may want to turn On the Compass for the next few steps.

  • right-click in the drawing area to invoke a shortcut menu and select Visual Aids then select Compass to turn it On.
  • you can repeat this step when you are ready to turn the Compass back Off again.

9) Right-click in the drawing area (with 3dorbit still running) to invoke a shortcut and select Reset View to prepare for the next step.

10) Left click near P1 (outside the arcball) and hold your mouse button down. Drag your cursor around the outside of the arcball to P2 then release your mouse button. Remain in the same 3dorbit command.

» 11) Right-click in the drawing area (with 3dorbit still running) to invoke a shortcut and select Reset View to prepare for the next step.

» 12) Left-click inside the small circle near P3 and hold the mouse button down. Drag the cursor to the left and release your mouse button when your model appears as shown. Remain in the same 3dorbit command.

When you left-click first in one of the small circles you will restrict the rotation about either a vertical or horizontal axis.

13) Right-click in the drawing area to invoke a shortcut and select More than select Continuous Orbit. Left-click on any point and hold your mouse button down. Drag your cursor slowly in any direction then release your mouse button to start spinning the model continuously.

You can left-click once at any time to stop the spinning

or drag again (while it is spinning) to change the way the model revolves around your screen.

» 14) While the model is still spinning, right-click in the drawing area to invoke a shortcut. Select Shading Modes and then pick Flat Shaded to change the shade mode.

15) Press <enter> to exit 3dcorbit.

More practice?

» 16)Close the current drawing file without saving changes.

» 17) Open the T302_5.dwg drawing in your personal folder.

18) Display the 3D Orbit toolbar.


19) Pick the
3dclip toolbar button on the 3D Orbit toolbar to open the Adjust Clipping Planes window. Drag your cursor (up and down) in this window and observe the effects of the moving front clipping plane in the drawing window.

20) Select the second button (Adjust Back Clipping) in the Adjust Clipping Plane window then turn the back clipping plane On by picking the last button in this window. Drag your cursor up and down in this window to observe the changes in your drawing window.

21) Close the Adjust Clipping Planes window. Press <enter> in AutoCAD to return to the Command line prompt.

The clipping planes remain on even though no command is running.

» 22) Pick View + 3D Orbit and right-click in the drawing area to invoke a shortcut. Select More then pick Continuous Orbit. Drag the model to spin it continuously on-screen.

» 23) When the model is still spinning on-screen, right-click in the drawing area to invoke a shortcut. Select More then pick Front Clipping On to toggle this plane Off. Repeat for the Back Clipping Plane to toggle it Off.

24) Right-click in the drawing area to invoke a shortcut and select Zoom. Reduce the magnification so the entire model fits on-screen.

25) Right-click in the drawing area to invoke a shortcut and select Projection then pick Perspective.

26) Right-click in the drawing area to invoke a shortcut and select More. Then pick Continuous Orbit. Try to create the impression that you are flying around this model.

Drag near the center of the window to create this illusion.

» 27) Press <enter> to return to the command prompt.

» 28) Close this file without saving changes.

More practice?

» 29) Open the T302_6.dwg drawing in your personal folder.

» 30) Display the View toolbar (if it is not already displayed).

» 31) Select the Camera button and use Center osnaps to select the SOLID spheres near P1 for the camera and P2 for the target points.

This is a simple 3D model of an office that has no surface for the ceiling or for the floor.

  • when you opened the drawing you were looking at this office from above (the Top view).
  • you just placed the camera inside the office to change the viewing direction.
  • the current Shademode is set to 2D Wireframe.

» 32) Pick View + Shade + Hidden.

The surface for the office walls obscures your view inside the office even though you placed the camera inside the office.

  • this is because Projection is still set to the default of Parallel.

» 33) Pick View + 3D Orbit. Right-click in the drawing area to invoke a shortcut. Pick Projection and select Perspective. Remain in 3dorbit.

The walls no longer obscure your view into the office now that you changed Projection to Perspective.

  • but if you moved the camera back (with 3ddistance) to a point outside the office, the walls would obscure your view again.

» 34) Right-click in the drawing area to invoke a shortcut. Select More then select Continuous Orbit. Drag your cursor slowly to simulate flying around the office.

The sphere you used (with a Center osnap) to specify the target point will remain stationary at the center of your screen.

  • the camera point is dynamically changing locations as you orbit the target point.
  • you also see another sphere, the one you used to select the initial camera point, fly by with each orbit.

More things to try?

» 35) Simulate different lens lengths (with perspective still selected for projection) by using the 3dzoom command. What effect does this have on the continuous orbit.

» 36) Change your 3ddistance to see what impact this has on the continuous orbit. How is this different from changing your lens length with 3dzoom?

» 37) Look around the office dynamically (in other directions) using the 3dswivel.

» 38) Close this drawing without saving the changes.

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