This removes the `From<Vec2/3>` implementations for the direction types.
It doesn't seem right to have when it only works if the vector is
nonzero and finite and produces NaN otherwise.
Added `Direction2d/3d::new` which uses `Vec2/3::try_normalize` to
guarantee it returns either a valid direction or `None`.
This should make it impossible to create an invalid direction, which I
think was the intention with these types.
# Objective
First, some terminology:
- **Minor radius**: The radius of the tube of a torus, i.e. the
"half-thickness"
- **Major radius**: The distance from the center of the tube to the
center of the torus
- **Inner radius**: The radius of the hole (if it exists), `major_radius
- minor_radius`
- **Outer radius**: The radius of the overall shape, `major_radius +
minor_radius`
- **Ring torus**: The familiar donut shape with a hole in the center,
`major_radius > minor_radius`
- **Horn torus**: A torus that doesn't have a hole but also isn't
self-intersecting, `major_radius == minor_radius`
- **Spindle torus**: A self-intersecting torus, `major_radius <
minor_radius`
Different tori from [Wikipedia](https://en.wikipedia.org/wiki/Torus),
where *R* is the major radius and *r* is the minor radius:
Currently, Bevy's torus is represented by a `radius` and `ring_radius`.
I believe these correspond to the outer radius and minor radius, but
they are rather confusing and inconsistent names, and they make the
assumption that the torus always has a ring.
I also couldn't find any other big engines using this representation;
[Godot](https://docs.godotengine.org/en/stable/classes/class_torusmesh.html)
and [Unity
ProBuilder](https://docs.unity3d.com/Packages/com.unity.probuilder@4.0/manual/Torus.html)
use the inner and outer radii, while
[Unreal](https://docs.unrealengine.com/5.3/en-US/BlueprintAPI/GeometryScript/Primitives/AppendTorus/)
uses the minor and major radii.
[Blender](https://docs.blender.org/manual/en/latest/modeling/meshes/primitives.html#torus)
supports both, but defaults to minor/major.
Bevy's `Torus` primitive should have an efficient, consistent, clear and
flexible representation, and the current `radius` and `ring_radius`
properties are not ideal for that.
## Solution
Change `Torus` to be represented by a `minor_radius` and `major_radius`.
- Mathematically correct and consistent
- Flexible, not restricted to ring tori
- Computations and conversions are efficient
- `inner_radius = major_radius - minor_radius`
- `outer_radius = major_radius + minor_radius`
- Mathematical formulae for things like area and volume rely on the
minor and major radii, no conversion needed
Perhaps the primary issue with this representation is that "minor
radius" and "major radius" are rather mathematical, and an inner/outer
radius can be more intuitive in some cases. However, this can be
mitigated with constructors and helpers.
# Objective
This PR adds some helpers for `Triangle2d` to work with its winding
order. This could also be extended to polygons (and `Triangle3d` once
it's added).
## Solution
- Add `WindingOrder` enum with `Clockwise`, `Counterclockwise` and
`Invalid` variants
- `Invalid` is for cases where the winding order can not be reliably
computed, i.e. the points lie on a single line and the area is zero
- Add `Triangle2d::winding_order` method that uses a signed surface area
to determine the winding order
- Add `Triangle2d::reverse` method that reverses the winding order by
swapping the second and third vertices
The API looks like this:
```rust
let mut triangle = Triangle2d::new(
Vec2::new(0.0, 2.0),
Vec2::new(-0.5, -1.2),
Vec2::new(-1.0, -1.0),
);
assert_eq!(triangle.winding_order(), WindingOrder::Clockwise);
// Reverse winding order
triangle.reverse();
assert_eq!(triangle.winding_order(), WindingOrder::Counterclockwise);
```
I also added tests to make sure the methods work correctly. For now,
they live in the same file as the primitives.
## Open questions
- Should it be `Counterclockwise` or `CounterClockwise`? The first one
is more correct but perhaps a bit less readable. Counter-clockwise is
also a valid spelling, but it seems to be a lot less common than
counterclockwise.
- Is `WindingOrder::Invalid` a good name? Parry uses
`TriangleOrientation::Degenerate`, but I'm not a huge fan, at least as a
non-native English speaker. Any better suggestions?
- Is `WindingOrder` fine in `bevy_math::primitives`? It's not specific
to a dimension, so I put it there for now.
# Add and implement constructors for Primitives
- Adds more Primitive types and adds a constructor for almost all of
them
- Works towards finishing #10572
## Solution
- Created new primitives
- Torus
- Conical Frustum
- Cone
- Ellipse
- Implemented constructors (`Primitive::new`) for almost every single
other primitive.
---------
Co-authored-by: Joona Aalto <jondolf.dev@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
- Implement a subset of
https://github.com/bevyengine/rfcs/blob/main/rfcs/12-primitive-shapes.md#feature-name-primitive-shapes
## Solution
- Define a very basic set of primitives in bevy_math
- Assume a 0,0,0 origin for most shapes
- Use radius and half extents to avoid unnecessary computational
overhead wherever they get used
- Provide both Boxed and const generics variants for shapes with
variable sizes
- Boxed is useful if a 3rd party crate wants to use something like
enum-dispatch for all supported primitives
- Const generics is useful when just working on a single primitive, as
it causes no allocs
#### Some discrepancies from the RFC:
- Box was changed to Cuboid, because Box is already used for an alloc
type
- Skipped Cone because it's unclear where the origin should be for
different uses
- Skipped Wedge because it's too niche for an initial PR (we also don't
implement Torus, Pyramid or a Death Star (there's an SDF for that!))
- Skipped Frustum because while it would be a useful math type, it's not
really a common primitive
- Skipped Triangle3d and Quad3d because those are just rotated 2D shapes
## Future steps
- Add more primitives
- Add helper methods to make primitives easier to construct (especially
when half extents are involved)
- Add methods to calculate AABBs for primitives (useful for physics, BVH
construction, for the mesh AABBs, etc)
- Add wrappers for common and cheap operations, like extruding 2D shapes
and translating them
- Use the primitives to generate meshes
- Provide signed distance functions and gradients for primitives (maybe)
---
## Changelog
- Added a collection of primitives to the bevy_math crate
---------
Co-authored-by: Joona Aalto <jondolf.dev@gmail.com>
