Max Richter
10a12ad41c
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52 lines
2.0 KiB
Rust
52 lines
2.0 KiB
Rust
use crate::{decode_float, encode_float};
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use glam::Vec3;
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pub fn calculate_normals(geometry: &mut [i32]) -> &mut [i32] {
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let vertex_count = geometry[1] as usize;
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let face_count = geometry[2] as usize;
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let index_start = 3;
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let indices_end = index_start + face_count * 3;
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let positions_start = indices_end;
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let positions_end = positions_start + vertex_count * 3;
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let normals_start = positions_end;
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let mut last_normal = Vec3::ZERO;
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for i in 0..face_count {
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let base_idx1 = geometry[index_start + i * 3] as usize * 3;
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let base_idx2 = geometry[index_start + i * 3 + 1] as usize * 3;
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let base_idx3 = geometry[index_start + i * 3 + 2] as usize * 3;
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let v1 = Vec3::new(
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decode_float(geometry[positions_start + base_idx1]),
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decode_float(geometry[positions_start + base_idx1 + 1]),
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decode_float(geometry[positions_start + base_idx1 + 2]),
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);
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let v2 = Vec3::new(
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decode_float(geometry[positions_start + base_idx2]) - v1.x,
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decode_float(geometry[positions_start + base_idx2 + 1]) - v1.y,
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decode_float(geometry[positions_start + base_idx2 + 2]) - v1.z,
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);
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let v3 = Vec3::new(
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decode_float(geometry[positions_start + base_idx3]) - v1.x,
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decode_float(geometry[positions_start + base_idx3 + 1]) - v1.y,
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decode_float(geometry[positions_start + base_idx3 + 2]) - v1.z,
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);
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let mut normal = v2.cross(v3).normalize();
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if normal.length_squared() == 0.0 {
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normal = last_normal;
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} else {
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last_normal = normal;
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}
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for j in 0..3 {
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let idx = geometry[index_start + i * 3 + j] as usize * 3;
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geometry[normals_start + idx] = encode_float(normal.x);
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geometry[normals_start + idx + 1] = encode_float(normal.y);
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geometry[normals_start + idx + 2] = encode_float(normal.z);
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}
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}
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geometry
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}
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