Cameras vs. views; views.xml

Question

Hi guys,
[Question 1]
I'm having problems defining and using appropriate user-defined cameras / views created within Acrobat 3D Toolkit.
What I would like to do is predefine a set of appropriate user-defined views based on exact angles within my U3D model, and use this set within 3D annotations embedded in PDF documents.
What I do not want are inexact views. I know that I could generate views by mouse-dragging (rotating) the scene within Acrobat 3D and saving the current view using the view snapshot button. That's not what I want.
First of all I think I understand the difference between using views vs. using cameras:
- When using views and clicking the left mouse button, the camera stays fixed, and the model is rotated about the center of the scene.
- When using cameras and clicking the left mouse button, the camera is rotated around its focal point.
I came up with the following workflow:
(1) Open a U3D model in Acrobat 3D Toolkit
(2) Select the desired view, e.g. 30° isometric view left top front, no perspective
(3) Create a new camera (which is based on the current view)
(4) Save the U3D model
(5) Embed the U3D model into a PDF document thus creating a new 3D annotation
(6) Import the cameras stored in the U3D model converting them into 3D annotation views
The problem is that the resulting 3D annotation views are cameras but not views. I.e. when the user activates such a view and drags the mouse, the camera will be rotated but not the model! If the camera is far enough away from the center of the scene, the model "escapes".
How can I solve this?
[Question 2]
Acrobat 3D Toolkit user manual:
p.51:
"Note: A sample views.xml is included with Acrobat 3D Toolkit and can be used as a template to define your custom views."
p.54:
User-defined views can be created either by creating camera objects or by defining the views in the views.xml file."
p.54:
"views.xml file: Views created using the views.xml file are non-positional. That is, they only control the angle of the camera. They are activated by using the Views menu (on page 293). Note that this file must be located in Acrobat 3D Toolkit's root installation folder for the views to be visible in the Views menu."
I have no such file in my Acrobat installation folder. Where can I get a sample views.xml file?
Thanks in advance for your help!
Best regards
Sebi

Answer 1

The issue with the camera orbiting around its center is due to a limitation of the U3D file format. U3D does not support the concept of a camera target object or position. This means that when cameras are imported from the file the information pertaining to their orbit distance is lost in the conversion.
The only way to really get around this shortcoming at the moment is to manually create the views in the PDF file with the correct camera target distance.
Another possible solution is to create the views and then add a JavaScript file that has a CameraEventHandler that updates the camera's target distance based up the camera information provided.
Something like the following:
viewManager = new CameraEventHandler();
viewManager.onEvent = function( event )
  if ( event.targetDistance == 1 )
    bb = scene.computeBoundingBox();
    cam = event.canvas.getCamera();
    dist = bb.center.subtract( cam.position ).length;
    dir = cam.targetPosition.subtract( cam.position );
    cam.targetPosition.set( cam.position.add( dir.scale( dist ) ) );
runtime.addEventHandler( viewManager );
Note: This will not work well for cameras placed very close to the exact center of the scene and added views that happen to have an exact target distance of 1 (very unlikely)