Navigation component

This component defines nodes to control the camera, and some effects closely related to the camera. NavigationInfo controls the camera behavior. Viewpoint and OrthoViewpoint define the initial camera position and rotation, and may be used to animate the camera. LOD allows to implement level-of-detail, where different versions of some object are displayed depending on the camera distance. Collision allows to use a simpler geometry for collision purposes, or even to turn the collisions off (like a fake wall hiding a secret room in games). Billboard may be used to create sprites, as it aligns geometry (flat or not) with respect to the camera.

See also X3D specification of the Navigation component.

Contents:

See also Castle Game Engine (and view3dscene) extensions related to navigation.

1. Demos

For demos and tests of these features, see the navigation subdirectory inside our VRML/X3D demo models.

2. Supported nodes

  • Viewpoint (API reference),
    OrthoViewpoint (API reference).

    These nodes define the initial camera position, rotation, and field of view. The Viewpoint makes a perspective projection (objects further away are smaller), OrthoViewpoint makes an orthographic projection.

    You can even animate their transformation and properties, to animate the camera.

    Note: In Castle Game Engine you can also control the camera by Pascal code, using the Viewport.Camera property that keeps a TCastleCamera instance. See manual about displaying scene and controlling the camera. Still, this X3D node is useful to set initial camera through e.g. Blender (you can export to glTF or X3D and importing them will set initial camera properly).

    view3dscene displays a nice menu allowing you to jump to any defined viewpoint, showing viewpoints' descriptions. Animating viewpoint's position and orientation (directly or by animating it's parent transformation) also works perfectly.

    TODO: We support most, but not all, X3D fields. Fields not implemented yet: jump, retainUserOffsets, centerOfRotation.

    • Support for centerOfRotation already exists in the engine (TExamineCamera.CenterOfRotation), so it should be easy to finish it (copy X3D Viewpoint.centerOfRotation to TExamineCamera.CenterOfRotation). But we may have to treat centerOfRotation = 0,0,0 as special value meaning "middle of the box", otherwise many models will have weird navigation because they lack correct centerOfRotation value (and the default is just zero).

      Suggestions and reports how does this work in other VRML/X3D browsers are welcome.

    • Support for jump and retainUserOffsets is probably easy, but someone has to actually understand the X3D specification about them, and explain how they are related to each other (and to NavigationInfo.transitionType). Suggestions and testcases and reports how do they work in other VRML/X3D browsers are welcome.

  • NavigationInfo (API reference)

    Controls the navigation behavior (mode of movement, gravity, etc.) and the headlight.

    Note: In Castle Game Engine you can also control the navigation by Pascal code, using the Viewport.Navigation property where you can assign an instance of some TCastleNavigation descendant. See manual about displaying scene and controlling the camera and navigation. And you can control the headlight using the Viewport.Items.UseHeadlight property. Still, this node is useful to define defaults.

    Details about supported fields:

    • avatarSize is honoured fully:

      1. First avatarSize item is the camera radius. If you use view3dscene, note that --camera-radius command-line option overrides this value.

      2. 2nd avatarSize item is the preferred height above the ground.

      3. 3rd avatarSize item is the tallest object over which you can climb.

        If this is missing (or it has value <= 0) then there's no such limit, and you can climb as long as you can move forward. So you can climb the stairs with steps almost as high as your own height minus the camera radius. Simplifying (ignoring other effects, like head bobbing), you can say that avatarSize[2] is by default like avatarSize[1] - avatarSize[0]).

        See TWalkCamera.ClimbHeight API docs for more details about this.

    • speed field is supported, it sets the speed in meters/second. Speed = 0.0 is also correctly honored (user will not be able to move in Walk/Fly modes, only to rotate).

    • type field is supported. Navigation types fully supported are: EXAMINE, WALK, FLY, NONE. Inside the engine, the navigation paradigm is actually a little more flexible. You can fine-tune the rotations and gravity behavior by view3dscene Navigation -> Walk and Fly Settings menu.

      As an extension, we also support new navigation mode TURNTABLE. This is similar to the Examine mode, with controls comfortable for viewing models that have a sense of floor/ground in the XZ plane, and vertical axis in +Y. Implementation is not finished yet.

      The presence of navigation type ANY is ignored by view3dscene. We always show controls to change navigation settings, hiding them feels harmful to user.

    • Nice transitions between viewpoints are supported, honouring transitionType and transitionTime fields, and (since view3dscene 3.13.0) making transitionComplete event. See demo model navigation/transition_multiple_viewpoints.x3dv showing how to use it to make an animated transition between a couple of viewpoints.

    Binding different NavigationInfo nodes, and changing their exposed fields by events, of course works.

    When no NavigationInfo node is present in the scene:

    • avatarSize and speed are calculated based on scene's bounding box sizes, to a values that will hopefully "feel right". We try to calculate them intelligently, because simply using NavigationInfo defaults results in bad experience in many scenes.
    • headlight behaves like true, type behaves like [EXAMINE, ANY], this follows NavigationInfo defaults.

    TODO: visibilityLimit may be ignored if shadow volumes are allowed (We use frustum with z-far in infinity then.)

  • LOD (API reference)

    Allows to define various versions of the same object, with varying level-of-detail. An appropriate child is automatically displayed based on the current distance to the camera.

    Note: Right now, the only thing that decides "which level of detail should be used" is the distance to the camera. Which means that only the supplied LOD.range controls which level is displayed. The forceTransitions value is simply ignored, and when range is empty, we simply always use the first (highest-detail) version.

    Example: The simplest example is part of our demo models. View the X3D code here: navigation/lod_test.x3dv.

  • Billboard (API reference)

    The children of this node are automatically aligned with the camera. Two modes are possible: where the objects are rotated only around a specified axis, or where objects are rotated freely to match the camera.

    Example: The simplest example is part of our demo models. View the X3D code here: navigation/billboard_simple.x3dv.

  • Collision (API reference)

    Allows to define a simpler geometry for collision purposes, or even to turn the collisions off (like a fake wall hiding a secret room in games).

    Most things work: grouping (children property, in particular), allows to control collision detection by honoring enabled (named collide in VRML 97) and proxy fields.

    bboxCenter/Size is currently simply ignored, our engine always calculates and updates the bounding boxes where needed.

    TODO: collideTime and isActive out events are not implemented yet.

  • ViewpointGroup (API reference)

    You can use this to create submenus in "Viewpoints" menu in view3dscene. Fields description and children are taken into account. Also, you can use this node to hide some viewpoints from the menu: the displayed field also works.

    TODO: size/center is not honored yet. Group is displayed regardless of camera position. A possible workarond could be to use a ProximitySensor node, routing ProximitySensor.isActive to the displayed field... Except this workaround will not work too, because changing of the displayed field after the scene loading doesn't change the menu for now.

    TODO: retainUserOffsets is ignored.