Spatial Integration can draw the scene with either a perspective or an orthographic camera. The two buttons at the right hand end of the status bar switch between them, and the button of the active mode is shown brightened.
The status bar buttons are, from left to right: legend, measure, screenshot, graticule, perspective view and orthographic view.
The view mode is saved with the project, so a project reopens in the mode it was last used in.
Perspective View
Perspective is the way we see the world: objects further from the camera are drawn smaller, and parallel lines converge towards the horizon. This gives a strong sense of depth and makes it much easier to judge which objects are in front of others.
Spatial Integration is designed to be used in perspective view. Navigation, scale and the general feel of the 3D scene all assume it, and it should be your normal working mode.
Orthographic View
In an orthographic view there is no convergence: an object is drawn at the same size no matter how far it is from the camera, and parallel lines stay parallel. Depth cues are lost, but everything in the image is drawn at exactly the same scale.
Orthographic view is intended for screen shots where you need a consistent scale across the whole image, for example a seismic or geological section, a plan of a drillhole collar layout, or a figure for a report where distances are to be measured off the printed page. Look square onto the section, switch to orthographic, then take the screen shot with the camera button or F12.
Switching modes does not jump the view. The orthographic extents are matched to the perspective field of view at the point you are looking at, so the scene stays the same size on screen and zooming continues to work as usual.
Adding a Scale
A graticule is a useful addition to an orthographic screen shot, because the labelled grid lines give the reader a scale that stays true across the entire image.