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refactoring
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@ciscorn
ciscorn committed Jun 9, 2024
1 parent 0fff2ad commit 47c2e23
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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@

Work in progress.

A 3D mesh voxelizer implemented in Rust using the DDA (Digital Differential Analyzer) algorithm. The DDA method is simple and very fast when you only want to voxelize the surfaces of meshes.
A 3D mesh voxelizer implemented in Rust using the DDA (Digital Differential Analyzer) algorithm. The DDA method is simple and very fast when only the surfaces (not volumes) of 3D objects need to be voxelized.

![1716994116122](docs/demo.png)

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40 changes: 34 additions & 6 deletions examples/voxelize.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -62,17 +62,20 @@ fn main() {
if project3d_to_2d(&buf3d, num_outer, &mut buf2d) {
// earcut
earcutter.earcut(buf2d.iter().cloned(), poly.hole_indices(), &mut index_buf);
for indx in index_buf.chunks_exact(3) {
for index in index_buf.chunks_exact(3) {
voxelizer.add_triangle(
&[
buf3d[indx[0] as usize],
buf3d[indx[1] as usize],
buf3d[indx[2] as usize],
buf3d[index[0] as usize],
buf3d[index[1] as usize],
buf3d[index[2] as usize],
],
&|_current_value, [x, y, z], _vertex_weight| {
let [x, y, z] = [x as f32, y as f32, z as f32];
let color_lab =
palette::Okhsl::new(x.atan2(z).to_degrees(), 1.0, y / 90. + 0.5);
let color_lab = palette::Okhsl::new(
x.atan2(z).to_degrees(),
1.0 - (x * x + z * z) / 2200.,
y / 90. + 0.5,
);
let color_srgb = palette::Srgb::from_color(color_lab);
[color_srgb.red, color_srgb.green, color_srgb.blue]
},
Expand All @@ -82,6 +85,31 @@ fn main() {
}
}

voxelizer.add_triangle(
&[[40., 40., 40.], [40., 40.6, 40.], [40., 40., 40.6]],
&|_, [x, y, z], _| {
let [x, y, z] = [x as f32, y as f32, z as f32];
let color_lab = palette::Okhsl::new(
x.atan2(z).to_degrees(),
1.0 - (x * x + z * z) / 2200.,
y / 90. + 0.5,
);
let color_srgb = palette::Srgb::from_color(color_lab);
[color_srgb.red, color_srgb.green, color_srgb.blue]
},
);

// voxelizer.add_line([40., 40., 40.], [40., 40., 40.], &|_, [x, y, z], _| {
// let [x, y, z] = [x as f32, y as f32, z as f32];
// let color_lab = palette::Okhsl::new(
// x.atan2(z).to_degrees(),
// 1.0 - (x * x + z * z) / 2200.,
// y / 90. + 0.5,
// );
// let color_srgb = palette::Srgb::from_color(color_lab);
// [color_srgb.red, color_srgb.green, color_srgb.blue]
// });

let occupied_voxels = voxelizer.finalize();

// -------------------make glTF-------------------
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166 changes: 63 additions & 103 deletions src/voxelize.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -69,9 +69,9 @@ fn draw_line<V: Clone>(
shader: &impl Shader<V>,
) {
let difference = end - start;
let mut current_voxel = (start + Vec3::splat(0.5)).floor().as_ivec3();
let last_voxel = (end + Vec3::splat(0.5)).floor().as_ivec3();

let mut current_voxel = (start + Vec3::splat(0.5)).floor().as_ivec3();
let step = difference.signum().as_ivec3();
let next_voxel_boundary = current_voxel.as_vec3() + 0.5 * step.as_vec3();
let mut tmax = (next_voxel_boundary - start) / difference;
Expand Down Expand Up @@ -107,29 +107,18 @@ fn fill_triangle<V: Clone>(
triangle: &[[f32; 3]; 3],
shader: &impl Shader<V>,
) {
let p1 = Vec3::from(triangle[0]);
let p2 = Vec3::from(triangle[1]);
let p3 = Vec3::from(triangle[2]);

// If the triangle is small enough, fill only the voxels corresponding to the three vertices.
if is_small_triangle(&p1, &p2, &p3) {
put_voxel(voxels, (p1 + Vec3::splat(0.5)).as_ivec3(), shader);
put_voxel(voxels, (p2 + Vec3::splat(0.5)).as_ivec3(), shader);
put_voxel(voxels, (p3 + Vec3::splat(0.5)).as_ivec3(), shader);
return;
}
let v0 = Vec3::from(triangle[0]);
let v1 = Vec3::from(triangle[1]);
let v2 = Vec3::from(triangle[2]);

let mut normal = (p2 - p1).cross(p3 - p1);
let mut normal = (v1 - v0).cross(v2 - v0);
let normal_length = normal.length();
if normal_length.is_nan() || normal_length == 0.0 {
// TODO: Should we draw a line when the triangle is colinear?
return;
}
normal /= normal_length;

// Find the axis of maximum length
// yz plane if norm_axis is 0(x)
// zx plane if norm_axis is 1(y)
// xy plane if norm_axis is 2(z)
let normal_axis = normal
.abs()
.to_array()
Expand All @@ -139,41 +128,25 @@ fn fill_triangle<V: Clone>(
.map(|(i, _)| i)
.unwrap();

let mut min_point = p1;
let mut max_point = p1;
for p in &[p2, p3] {
min_point = min_point.min(*p);
max_point = max_point.max(*p);
}
let box_size = max_point - min_point;

let sweep_axis = match normal_axis {
0 => {
if box_size[1] >= box_size[2] {
1
} else {
2
}
}
1 => {
if box_size[2] >= box_size[0] {
2
} else {
0
}
}
2 => {
if box_size[0] >= box_size[1] {
0
} else {
1
}
// Determine the axis to sweep along
let sweep_axis = {
let min_point = v0.min(v1).min(v2);
let max_point = v0.max(v1).max(v2);
let box_size = max_point - min_point;

// Which axis is the triangle's normal closer to?
match normal_axis {
0 if box_size[1] >= box_size[2] => 1,
0 => 2,
1 if box_size[2] >= box_size[0] => 2,
1 => 0,
2 if box_size[0] >= box_size[1] => 0,
2 => 1,
_ => unreachable!(),
}
_ => unreachable!(),
};

// Draw a virtual grid along the x-axis and find the intersection of the target triangle and the edge
// Paint from the intersection with smaller x to the intersection with larger x
// Reorder the vertices to arrange sequentially along the sweep axis
let mut ordered_verts = [triangle[0], triangle[1], triangle[2]];
if ordered_verts[0][sweep_axis] > ordered_verts[1][sweep_axis] {
ordered_verts.swap(0, 1);
Expand All @@ -186,70 +159,57 @@ fn fill_triangle<V: Clone>(
}
debug_assert!(ordered_verts[1][sweep_axis] >= ordered_verts[0][sweep_axis]);

let ordered_verts: [[f32; 3]; 3] = ordered_verts.map(|inner| inner.map(|x| x));

let [mut start_step, mut start_pos] =
if (ordered_verts[1][sweep_axis] - ordered_verts[0][sweep_axis]).abs() >= 0.0
&& (ordered_verts[1][sweep_axis] - ordered_verts[0][sweep_axis].floor() >= 1.0)
{
let start_step = (Vec3::from(ordered_verts[1]) - Vec3::from(ordered_verts[0]))
/ (ordered_verts[1][sweep_axis] - ordered_verts[0][sweep_axis]);
let start_pos = Vec3::from(ordered_verts[0])
+ start_step
* ((1.0 - ordered_verts[0][sweep_axis] + ordered_verts[0][sweep_axis].floor())
% 1.0);
[start_step, start_pos]
} else {
let start_step = (Vec3::from(ordered_verts[2]) - Vec3::from(ordered_verts[1]))
/ (ordered_verts[2][sweep_axis] - ordered_verts[1][sweep_axis]);
let start_pos = Vec3::from(ordered_verts[1])
+ start_step
* ((1.0 - ordered_verts[1][sweep_axis] + ordered_verts[1][sweep_axis].floor())
% 1.0);
[start_step, start_pos]
};
let v0 = Vec3::from(ordered_verts[0]);
let v1 = Vec3::from(ordered_verts[1]);
let v2 = Vec3::from(ordered_verts[2]);

let end_step = (Vec3::from(ordered_verts[2]) - Vec3::from(ordered_verts[0]))
/ (ordered_verts[2][sweep_axis] - ordered_verts[0][sweep_axis]);
let mut end_pos = Vec3::from(ordered_verts[0])
let end_step = (v2 - v0) / (ordered_verts[2][sweep_axis] - ordered_verts[0][sweep_axis]);
let mut end_pos = v0
+ end_step
* ((1.0 - ordered_verts[0][sweep_axis] + ordered_verts[0][sweep_axis].floor()) % 1.0);

let mut end_vertex_y = ordered_verts[1][sweep_axis];
let start_step1 = (v1 - v0) / (ordered_verts[1][sweep_axis] - ordered_verts[0][sweep_axis]);
let start_step2 = (Vec3::from(ordered_verts[2]) - Vec3::from(ordered_verts[1]))
/ (ordered_verts[2][sweep_axis] - ordered_verts[1][sweep_axis]);
let mut start_pos = v0
+ start_step1
* ((1.0 - ordered_verts[0][sweep_axis] + ordered_verts[0][sweep_axis].floor()) % 1.0);

if start_step.length() > 1000.0 || end_step.length() > 1000.0 {
log::debug!("Direction vector magnitude is too large");
if start_step1.length() > 1000.0 || start_step2.length() > 1000.0 || end_step.length() > 1000.0
{
log::debug!("Step vector magnitude is too large");
return;
}

while end_pos[sweep_axis] <= ordered_verts[2][sweep_axis] {
draw_line(voxels, start_pos, end_pos, shader);
if start_step1[sweep_axis].is_finite() {
// Start position is on the first edge
while start_pos[sweep_axis] < ordered_verts[1][sweep_axis] + 0.5 {
draw_line(voxels, start_pos, end_pos, shader);
start_pos += start_step1;
end_pos += end_step;
}

start_pos += start_step;
end_pos += end_step;
// Switch to the second edge
let end_vertex_y = ordered_verts[1][sweep_axis] - start_pos[sweep_axis];
start_pos += (start_step1 - start_step2) * end_vertex_y;
} else {
// Switch to the second edge
start_pos = Vec3::from(ordered_verts[1])
+ start_step2
* ((1.0 - ordered_verts[1][sweep_axis] + ordered_verts[1][sweep_axis].floor())
% 1.0);
}

if start_pos[sweep_axis] >= end_vertex_y {
end_vertex_y = start_pos[sweep_axis] - ordered_verts[1][sweep_axis];
start_pos -= start_step * end_vertex_y;
if (ordered_verts[2][sweep_axis] - ordered_verts[1][sweep_axis]).abs() == 0.0 {
continue;
}
start_step = (Vec3::from(ordered_verts[2]) - Vec3::from(ordered_verts[1]))
/ (ordered_verts[2][sweep_axis] - ordered_verts[1][sweep_axis]);
start_pos += start_step * end_vertex_y;
end_vertex_y = ordered_verts[2][sweep_axis];
if start_step2[sweep_axis].is_finite() {
// Start position is on the second edge
while end_pos[sweep_axis] < ordered_verts[2][sweep_axis] + 0.5 {
draw_line(voxels, start_pos, end_pos, shader);
start_pos += start_step2;
end_pos += end_step;
}
}
}

fn is_small_triangle(p1: &Vec3, p2: &Vec3, p3: &Vec3) -> bool {
let d12 = p1.distance(*p2);
let d23 = p2.distance(*p3);
let d31 = p3.distance(*p1);

d12 <= 1.0 && d23 <= 1.0 && d31 <= 1.0
}

#[cfg(test)]
mod tests {
use super::*;
Expand Down Expand Up @@ -294,12 +254,12 @@ mod tests {

if project3d_to_2d(&buf3d, num_outer, &mut buf2d) {
earcutter.earcut(buf2d.iter().cloned(), poly.hole_indices(), &mut index_buf);
for indx in index_buf.chunks_exact(3) {
for index in index_buf.chunks_exact(3) {
voxelizer.add_triangle(
&[
buf3d[indx[0] as usize],
buf3d[indx[1] as usize],
buf3d[indx[2] as usize],
buf3d[index[0] as usize],
buf3d[index[1] as usize],
buf3d[index[2] as usize],
],
&|_, _, _| true,
);
Expand Down

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