From 1196186257e785e268bb61f2759c88e9d1be3664 Mon Sep 17 00:00:00 2001
From: Lynn <62256001+lynn-lumen@users.noreply.github.com>
Date: Mon, 10 Jun 2024 14:50:29 +0200
Subject: [PATCH] Add segments to `ExtrusionBuilder` (#13719)
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# Objective
- Add support for `segments` for extrusion-meshes, akin to what is
possible with cylinders
## Solution
- Added a `.segments(segments: usize)` function to `ExtrusionBuilder`.
- Implemented support for segments in the meshing algorithm.
- If you set `.segments(0)`, the meshing will fail, just like it does
with cylinders.
## Additional information
Here is a wireframe of some extrusions with 1, 2, 3, etc. segments:
---------
Co-authored-by: Lynn Büttgenbach <62256001+solis-lumine-vorago@users.noreply.github.com>
---
.../src/mesh/primitives/extrusion.rs | 146 +++++++++++-------
1 file changed, 92 insertions(+), 54 deletions(-)
diff --git a/crates/bevy_render/src/mesh/primitives/extrusion.rs b/crates/bevy_render/src/mesh/primitives/extrusion.rs
index 1a4fcc662695a..96cfbba9fb9b3 100644
--- a/crates/bevy_render/src/mesh/primitives/extrusion.rs
+++ b/crates/bevy_render/src/mesh/primitives/extrusion.rs
@@ -91,6 +91,7 @@ where
ExtrusionBuilder {
base_builder: self.base_shape.mesh(),
half_depth: self.half_depth,
+ segments: 1,
}
}
}
@@ -101,8 +102,9 @@ where
P: Primitive2d + Meshable,
P::Output: Extrudable,
{
- base_builder: P::Output,
- half_depth: f32,
+ pub base_builder: P::Output,
+ pub half_depth: f32,
+ pub segments: usize,
}
impl ExtrusionBuilder
@@ -115,8 +117,16 @@ where
Self {
base_builder: base_shape.mesh(),
half_depth: depth / 2.,
+ segments: 1,
}
}
+
+ /// Sets the number of segments along the depth of the extrusion.
+ /// Must be greater than `0` for the geometry of the mantel to be generated.
+ pub fn segments(mut self, segments: usize) -> Self {
+ self.segments = segments;
+ self
+ }
}
impl ExtrusionBuilder {
@@ -218,14 +228,19 @@ where
panic!("The base mesh did not have vertex positions");
};
+ debug_assert!(self.segments > 0);
+
+ let layers = self.segments + 1;
+ let layer_depth_delta = self.half_depth * 2.0 / self.segments as f32;
+
let perimeter = self.base_builder.perimeter();
let (vert_count, index_count) =
perimeter
.iter()
.fold((0, 0), |(verts, indices), perimeter| {
(
- verts + 2 * perimeter.vertices_per_layer(),
- indices + perimeter.indices_per_segment(),
+ verts + layers * perimeter.vertices_per_layer(),
+ indices + self.segments * perimeter.indices_per_segment(),
)
});
let mut positions = Vec::with_capacity(vert_count);
@@ -253,36 +268,37 @@ where
// Get the index of the next vertex added to the mantel.
let index = positions.len() as u32;
- // Push the positions of the two indices and their equivalent points on the back face.
- // This works, since the front face has already been moved to the correct depth.
- positions.push(a);
- positions.push(b);
- positions.push([a[0], a[1], -a[2]]);
- positions.push([b[0], b[1], -b[2]]);
-
- // UVs for the mantel are between (0, 0.5) and (1, 1).
- uvs.extend_from_slice(&[
- [uv_x, 0.5],
- [uv_x + uv_delta, 0.5],
- [uv_x, 1.],
- [uv_x + uv_delta, 1.],
- ]);
+ // Push the positions of the two indices and their equivalent points on each layer.
+ for i in 0..layers {
+ let i = i as f32;
+ let z = a[2] - layer_depth_delta * i;
+ positions.push([a[0], a[1], z]);
+ positions.push([b[0], b[1], z]);
+
+ // UVs for the mantel are between (0, 0.5) and (1, 1).
+ let uv_y = 0.5 + 0.5 * i / self.segments as f32;
+ uvs.push([uv_x, uv_y]);
+ uvs.push([uv_x + uv_delta, uv_y]);
+ }
// The normal is calculated to be the normal of the line segment connecting a and b.
let n = Vec3::from_array([b[1] - a[1], a[0] - b[0], 0.])
.normalize_or_zero()
.to_array();
- normals.extend_from_slice(&[n; 4]);
+ normals.extend_from_slice(&vec![n; 2 * layers]);
// Add the indices for the vertices created above to the mesh.
- indices.extend_from_slice(&[
- index,
- index + 2,
- index + 1,
- index + 1,
- index + 2,
- index + 3,
- ]);
+ for i in 0..self.segments as u32 {
+ let base_index = index + 2 * i;
+ indices.extend_from_slice(&[
+ base_index,
+ base_index + 2,
+ base_index + 1,
+ base_index + 1,
+ base_index + 2,
+ base_index + 3,
+ ]);
+ }
}
}
PerimeterSegment::Smooth {
@@ -296,14 +312,22 @@ where
// we need to store the index of the first vertex that is part of this segment.
let base_index = positions.len() as u32;
- // If there is a first vertex, we need to add it and its counterpart on the back face.
+ // If there is a first vertex, we need to add it and its counterparts on each layer.
// The normal is provided by `segment.first_normal`.
if let Some(i) = segment_indices.first() {
let p = cap_verts[*i as usize];
- positions.push(p);
- positions.push([p[0], p[1], -p[2]]);
- uvs.extend_from_slice(&[[uv_start, 0.5], [uv_start, 1.]]);
- normals.extend_from_slice(&[first_normal.extend(0.).to_array(); 2]);
+ for i in 0..layers {
+ let i = i as f32;
+ let z = p[2] - layer_depth_delta * i;
+ positions.push([p[0], p[1], z]);
+
+ let uv_y = 0.5 + 0.5 * i / self.segments as f32;
+ uvs.push([uv_start, uv_y]);
+ }
+ normals.extend_from_slice(&vec![
+ first_normal.extend(0.).to_array();
+ layers
+ ]);
}
// For all points inbetween the first and last vertices, we can automatically compute the normals.
@@ -315,11 +339,15 @@ where
let b = cap_verts[segment_indices[i] as usize];
let c = cap_verts[segment_indices[i + 1] as usize];
- // Add the current vertex and its counterpart on the backface
- positions.push(b);
- positions.push([b[0], b[1], -b[2]]);
+ // Add the current vertex and its counterparts on each layer.
+ for i in 0..layers {
+ let i = i as f32;
+ let z = b[2] - layer_depth_delta * i;
+ positions.push([b[0], b[1], z]);
- uvs.extend_from_slice(&[[uv_x, 0.5], [uv_x, 1.]]);
+ let uv_y = 0.5 + 0.5 * i / self.segments as f32;
+ uvs.push([uv_x, uv_y]);
+ }
// The normal for the current vertices can be calculated based on the two neighbouring vertices.
// The normal is interpolated between the normals of the two line segments connecting the current vertex with its neighbours.
@@ -333,32 +361,42 @@ where
.extend(0.)
.to_array()
};
- normals.extend_from_slice(&[n; 2]);
+ normals.extend_from_slice(&vec![n; layers]);
}
- // If there is a last vertex, we need to add it and its counterpart on the back face.
+ // If there is a last vertex, we need to add it and its counterparts on each layer.
// The normal is provided by `segment.last_normal`.
if let Some(i) = segment_indices.last() {
let p = cap_verts[*i as usize];
- positions.push(p);
- positions.push([p[0], p[1], -p[2]]);
- uvs.extend_from_slice(&[
- [uv_start + uv_segment_delta, 0.5],
- [uv_start + uv_segment_delta, 1.],
+ for i in 0..layers {
+ let i = i as f32;
+ let z = p[2] - layer_depth_delta * i;
+ positions.push([p[0], p[1], z]);
+
+ let uv_y = 0.5 + 0.5 * i / self.segments as f32;
+ uvs.push([uv_start + uv_segment_delta, uv_y]);
+ }
+ normals.extend_from_slice(&vec![
+ last_normal.extend(0.).to_array();
+ layers
]);
- normals.extend_from_slice(&[last_normal.extend(0.).to_array(); 2]);
}
- for i in 0..(segment_indices.len() as u32 - 1) {
- let index = base_index + 2 * i;
- indices.extend_from_slice(&[
- index,
- index + 1,
- index + 2,
- index + 2,
- index + 1,
- index + 3,
- ]);
+ let columns = segment_indices.len() as u32;
+ let segments = self.segments as u32;
+ let layers = segments + 1;
+ for s in 0..segments {
+ for column in 0..(columns - 1) {
+ let index = base_index + s + column * layers;
+ indices.extend_from_slice(&[
+ index,
+ index + 1,
+ index + layers,
+ index + layers,
+ index + 1,
+ index + layers + 1,
+ ]);
+ }
}
}
}