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# Objective Introduce isometry types for describing relative and absolute position in mathematical contexts. ## Solution For the time being, this is a very minimal implementation. This implements the following faculties for two- and three-dimensional isometry types: - Identity transformations - Creation from translations and/or rotations - Inverses - Multiplication (composition) of isometries with each other - Application of isometries to points (as vectors) - Conversion of isometries to affine transformations There is obviously a lot more that could be added, so I erred on the side of adding things that I knew would be useful, with the idea of expanding this in the near future as needed. (I also fixed some random doc problems in `bevy_math`.) --- ## Design One point of interest here is the matter of if/when to use aligned types. In the implementation of 3d isometries, I used `Vec3A` rather than `Vec3` because it has no impact on size/alignment, but I'm still not sure about that decision (although it is easily changed). For 2d isometries — which are encoded by four floats — the idea of shoving them into a single 128-bit buffer (`__m128` or whatever) sounds kind of enticing, but it's more involved and would involve writing unsafe code, so I didn't do that for now. ## Future work - Expand the API to include shortcuts like `inverse_mul` and `inverse_transform` for efficiency reasons. - Include more convenience constructors and methods (e.g. `from_xy`, `from_xyz`). - Refactor `bevy_math::bounding` to use the isometry types. - Add conversions to/from isometries for `Transform`/`GlobalTransform` in `bevy_transform`. |
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Bevy Math
