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bevy_render: Fix Quad flip (#3741)

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# Objective

The documentation was unclear but it seemed like it was intended to _only_ flip the texture coordinates of the quad. However, it was also swapping the vertex positions, which resulted in inverted winding order so the front became a back face, and the normal was pointing into the face instead of out of it.

## Solution

- This change makes the only difference the UVs being horizontally flipped.
This commit is contained in:
Robert Swain 2022-02-12 00:46:04 +00:00
parent 6475268351
commit 0ccb9dd07e
1 changed files with 8 additions and 52 deletions
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60
crates/bevy_render/src/mesh/shape/mod.rs
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@ -125,7 +125,7 @@ impl From<Box> for Mesh {
pub struct Quad {
/// Full width and height of the rectangle.
pub size: Vec2,
/// Flips the texture coords of the resulting vertices.
/// Horizontally-flip the texture coordinates of the resulting mesh.
pub flip: bool,
}
@ -150,57 +150,13 @@ impl From<Quad> for Mesh {
let extent_x = quad.size.x / 2.0;
let extent_y = quad.size.y / 2.0;
let north_west = vec2(-extent_x, extent_y);
let north_east = vec2(extent_x, extent_y);
let south_west = vec2(-extent_x, -extent_y);
let south_east = vec2(extent_x, -extent_y);
let vertices = if quad.flip {
[
(
[south_east.x, south_east.y, 0.0],
[0.0, 0.0, 1.0],
[1.0, 1.0],
),
(
[north_east.x, north_east.y, 0.0],
[0.0, 0.0, 1.0],
[1.0, 0.0],
),
(
[north_west.x, north_west.y, 0.0],
[0.0, 0.0, 1.0],
[0.0, 0.0],
),
(
[south_west.x, south_west.y, 0.0],
[0.0, 0.0, 1.0],
[0.0, 1.0],
),
]
} else {
[
(
[south_west.x, south_west.y, 0.0],
[0.0, 0.0, 1.0],
[0.0, 1.0],
),
(
[north_west.x, north_west.y, 0.0],
[0.0, 0.0, 1.0],
[0.0, 0.0],
),
(
[north_east.x, north_east.y, 0.0],
[0.0, 0.0, 1.0],
[1.0, 0.0],
),
(
[south_east.x, south_east.y, 0.0],
[0.0, 0.0, 1.0],
[1.0, 1.0],
),
]
};
let (u_left, u_right) = if quad.flip { (1.0, 0.0) } else { (0.0, 1.0) };
let vertices = [
([-extent_x, -extent_y, 0.0], [0.0, 0.0, 1.0], [u_left, 1.0]),
([-extent_x, extent_y, 0.0], [0.0, 0.0, 1.0], [u_left, 0.0]),
([extent_x, extent_y, 0.0], [0.0, 0.0, 1.0], [u_right, 0.0]),
([extent_x, -extent_y, 0.0], [0.0, 0.0, 1.0], [u_right, 1.0]),
];
let indices = Indices::U32(vec![0, 2, 1, 0, 3, 2]);