4. Turn a 3D View into an Answer

This is where PurpleGeo becomes more than a way to look at point clouds. The important operations are often modest: find a useful plane through the data, take a dimension, mark the feature, or compare two dates. They let you turn an impression into something another person can evaluate.

Cross Section: a working 2D plane inside the 3D site

A cross section is not simply another camera angle. It establishes a vertical drawing and inspection plane through the 3D data, giving you a side-on, orthographic view at the location you choose. The distinction matters: complicated geometry can become much easier to reason about once you put the section in the right place.

1. Choose Cross Section.
2. Left-drag a line across the area of interest in Map or over the data in 3D.
3. Release to enter a side-on orthographic section view.
4. Adjust Cross Section Thickness to show a thinner or thicker slab.
5. Left-drag to pan; scroll or right-drag to zoom. Use W/S to move the slab forward or backward, with Shift/Ctrl for faster/slower movement.

The section keeps horizontal and vertical scales equal, without vertical exaggeration. A thick slab includes more depth but can clutter the profile; a thin slab separates features but may contain fewer points. Start reasonably thick so you can find the feature, then thin the section if nearby geometry is obscuring it. Step the plane along the site to see how the section changes.

Choose another camera mode to leave the section view. The current section plane is vertical; this is not yet an arbitrary inclined or oblique cutting plane.

Why sections are particularly useful

Consider a laser scan of an existing plant room where a boiler or piece of machinery is being replaced. The interesting question may not be Can I model the entire room? It may be:

• How wide is the space between the wall and the adjacent equipment?
• Where are the relevant pipes, penetrations, and obstructions?
• At what height do they cross the proposed installation area?
• What few dimensions need checking on site before anything is fabricated?

A carefully placed section turns a busy 3D scan into a readable 2D working view. You can use annotations and measurements on that view to record the observations that matter. A couple of sections can be much more useful to the next person than a beautiful but ambiguous general-purpose 3D perspective.

The same principle applies outdoors. Across an embankment, trench, channel, cut slope, or roadway, a section makes width, shape, grade changes, and local geometry easier to inspect. Moving the section a short distance can reveal whether the shape you saw is representative or just one isolated feature.

Important distinction: The section is a way of viewing and working with the existing points. It does not automatically create a finished 2D CAD drawing, prove an installation path is clear, or crop the cloud for export. Drawing-style annotations in a section are useful, but still need appropriate checking and downstream documentation for formal design or fabrication.