Viewpoint and lighting

Overview:

The View tab can be used to control both the viewpoint and the scene lighting, and displays the current settings for both.

When visualizing data in the VAPOR GUI, the 3D scene is shown in the visualizer window as if viewed from a camera positioned a a particular place in 3D space, pointed in a particular direction.  

Various ways of controlling the viewpoint in VAPOR GUI:

The viewpoint in VAPOR GUI can be controlled by various controls in the main window, as well as by using controls in the View tab.

Viewpoint navigation:  The easiest way to control the viewpoint is by using the mouse in the scene as follows:

• Dragging the mouse in the scene while pressing the left mouse button will rotate the scene relative to the center of view.
• Dragging up or down while pressing the right mouse button will result in zooming in or out of the scene
• Dragging with the middle mouse button pressed will pan the viewpoint in the direction you drag the mouse.

More information about mouse control is provided in the discussion of manipulators and mouse modes.

Main window viewpoint controls:  There are several buttons and selectors at the top of the VAPOR GUI main window that are useful in controlling the viewpoint, as follows:

The leftmost selector ("Visualizer No. 0") controls which visualizer is the current active visualizer and allows creation of a new visualizer.

The next two buttons: enable rearrangement of visualizer windows, as described where multiple visualizers are discussed.

Clicking on the Home button causes the viewpoint to be reset to the current "Home" viewpoint (which is initially the default viewpoint, looking down negative Z axis at teh center of the data volume). 

You can set the home viewpoint by clicking on the "Set Home" button: .

The Magnifying glass sets the view so as to focus on the current region. 

The "eye" or "View all" button will reset the viewpoint so that the entire domain is visible in the scene.

When you select the "Align View" selector you are presented with a choice of axis-aligned viewpoints:

Viewpoint settings in View Tab: Full control of the viewpoint is provided in the View tab.  The viewing parameters are specified at the top of the View tab as follows:

• The "view direction" is a 3-vector specifying the direction in which the camera is pointed.
• The "up vector" is a vector in the scene that is aligned with the upward direction of the camera.
• The "camera position" is a 3D point in the scene where the camera is located.
• The "rotation center" is a 3D point in the scene that is used as the center of rotation when the user rotates the scene by dragging with the left mouse button.  This point is set to the center of the current region when you click on the magnifying glass button.  When you use the middle mouse to pan the view, the rotation center is not moved.

The camera view subtends a 45 degree angle horizontally (i.e. there is a 45 degree view frustum).  This angle cannot be modified.

Setting the view from the Probe:  Often it is important to center the view at a particular position in space, or to set the center of rotation at a point of interest that you would like to observe closely or rotate around.  This can easily be done using the Probe.  Position the probe at a place near where you are interested in observing, and then, at the bottom of the Probe Image Settings, click the button labeled "Use selected point to center:... View".  This will make the Probe cursor position become the center of rotation, and also will move the camera so as to point directly at the probe cursor.  This view setting can also be done with the 2D and Image panels.

Stereoscopic Rendering:

Stereoscopic rendering has been introduced in VAPOR 2.5, wherein users can create real-time visualizations of their data in 3D.  This requires a graphics card that supports quad-buffered stereo rendering, a 3D display, and 3D stereo glasses.  Once these hardware requirements are met, users can check the "Enable stereo settings at startup" checkbox under the User Preferences menu.  This setting will require VAPOR to be restarted before it takes effect.  

After restarting, stereo rendering can be applied with the "Stereo Enabled" checkbox in the View tab.  The "Convergence" slider bar allows users to cast the 3D scene in front of the screen or behind it.  A convergence value of -1 will bring the scene close to the viewer, and a value of 1 will place the scene away from the viewer.

Release availability: version 2.5 and beyond.

Lighting control:

VAPOR GUI allows the user to specify up to three directional light sources.  The DVR and the Isosurface renderer use only the first light source.  Other visualizers use all specified light sources.  The properties of these lights are set at the bottom of the View panel:

VAPOR GUI simulates white light sources.  For each light source the lighting orientation specifies a direction vector, indicating the direction of the light source relative to the camera direction.  The first light source has by default a direction vector of (0,0,1), indicating that its direction is the same as the camera direction, as if the light is positioned behind the camera.

Each light source has diffuse and specular components, which should be set to values between 0 and 1.  There is also an ambient coefficient, indicating the contribution of a directionless ambient light, and a shininess exponent that applies to all lights with nonzero specular coefficients.