Drawing dynamic primitives in RealityKit

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Created Jun ’20

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Is it possible to use RealityKit to draw dynamic primitives?
...like a thin cylinder between 2 dynamically changing location anchors for example?
Or is that still something I need to build using SceneKit?

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Answer 1

Vision Pro Engineer OP

Apple

Jul ’20

You can create primitives programmatically in RealityKit. To create a cylinder, you can use generateBox(size:cornerRadius:) with the corner radius set to half of the box's width.
https://developer.apple.com/documentation/realitykit/meshresource/3244417-generatebox

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Answer 2

maxxfrazer OP

Jul ’20

If you want an actual cylinder the .generateBox with cornerRadius method might not be the best option, as it will give you a capsule shape.

Seeing as RealityKit doesn’t let you generate a Cylinder normally I’ve had to be a little creative when doing this; the best method I’ve found, albeit dirty, is using generateText().

The steps are:

Add mesh using .generateText(“.”) to a ModelEntity
use visualBounds method to check what dimensions it has given the cylinder
using the visual bounds .extents change the scale of the ModelEntity to match [1, 1, 1]
set the position of ModelEntity to negative .center
make this ModelEntity the child of another Entity (just to simplify scale and rotations)

Then you’ll have a cylinder along the Z axis with dimensions the same as the Entity. However you cannot specify the number of segments or the level of detail using generateText(), like you can with SCNCylinder.

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