Tooling to generate Mesh Cross-Sections projected onto a plane at a selected location.

Tooling appears in the Edit/Object mode UI under "Cross Section Tools" And the X-Plane ACF body exporter appears in the export menu.

To generate cross sections, a selection should contain at least two objects the active object is taken as the definition for the cutting plane on which the cross-section will be projected. The X/Y axis define the plane and the Z the normal. For each of the other selected components, if they are meshes, a cross-section mesh object named "Section(.n)" is generated if the plane cuts any part of the selected object.

In addition there is an option to generate sampled curves from the inner or outer surfaces at each cross section, the number of sample points can be selected, and the curve can either be generated as a Bezier or a Polyline. The sampling works by 'ray tracing' from the center of the bounding box outward and taking the first (inner) or last (outer) intersection with the section meshes along each ray. This works for relatively simple shapes cylinders basically things like an aircraft fuselage! Complex folded shapes an I-beam for instance will not surface detect correctly, you can still generate the cross-sectional meshes but surface detection will be a manual process.

Finally the exporter option will write the data from a set of cross sections in an X-Plane 'Body' format into an export file, the idea is that you can select the content of the file, cut and paste it into an actual ACF file to obtain the profile of the body. Select the set of surface curves and hit the export button!

The 'Generate' button will only activate if there are at least two selected items, and one of them is active. The Active object label will display the name of the object to be used as the cutting plane.

The second screenshot below shows a cross-section generated with the cutting plane rotated about the X axis

The next shot shows a more complex model comprised of several objects and internal structure (an aircraft engine nacelle) The slicing plane is defined by the arrowed empty at the nose.

In this case the empty carries a number of optional custom properties

z_samples: The z_samples is a float array containing offset distances to generate a number of cross sections stepping back the z ordinate by the given amounts:

z_adjust:By default the exporter will set the Z 0 position as the position of the highest Z in the samples. The z_adjust is basically used to modify the exported 0 position, in this case the X-Plane 'engine' location is a little to the right of the spinner tip, so we add 43.3cm offset

body_id: The exporter will generate a body '0' by default, if this property is specified then the output data will contain an appropriately numbered body

The next screen shows the content of the 'redo' panel

The 'Generate Meshes' panel indicates whether the meshes remain in the model on completion (they are always generated to be sampled but are only kept if this is checked)

The 'Generate Curve' option controls the sampling of the meshes into surface curves. If selected the Curve config options willbe shown

The 'Generate bezier curve' option will use a 'Bezier' representation of the surface, if not selected then a 'Polyline' will be produced instead (for X-Plane this is probably more appropriate)

The 'Outer surface' option selects the furthest from the center sample as the surface, unchecked the nearest to center inner face will be sampled.

The 'sample Half section' option chooses to take a 0-180 set of samples, unchecked this will take 0-360 (and importantly twice the number of samples selected below)

The 'Number of samples' option selects how many sample points are taken (0 and 180 are always present others are spaced between)

Save sample angles will write a float array custom property to the plane definition object 'sample_angles' with the set of angles at which samples are taken, if this is present when generating the curves, the content will override the default equally spaced sampling angles and can be used to sample at angles which better follow contours of the body being sampled.

The next shot shows the sampled curves for the nacelle

And the next one shows the mesh cross sections generated. The front green one shows some internal structure and the rear white one s actually composed of two meshes from two separate components. Thes have been sampled in the previous shot to give the 'outer' surface curves shown