1 files changed, 81 insertions, 0 deletions
diff --git a/client/src/render/scene/meshops.rs b/client/src/render/scene/meshops.rs
new file mode 100644
index 0000000..0a3f963
--- /dev/null
+++ b/client/src/render/scene/meshops.rs
@@ -0,0 +1,81 @@
+/*
+    wearechat - generic multiplayer game with voip
+    Copyright (C) 2025 metamuffin
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, version 3 of the License only.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+use glam::{Vec2, Vec3, vec2};
+
+pub fn generate_normals(index: &[[u32; 3]], position: &[Vec3]) -> Vec<Vec3> {
+    let mut normal_denom = vec![0; position.len()];
+    let mut normal = vec![Vec3::ZERO; position.len()];
+
+    for &[a, b, c] in index {
+        let pos_a = position[a as usize];
+        let pos_b = position[b as usize];
+        let pos_c = position[c as usize];
+
+        // TODO is this right?
+        let norm = (pos_b - pos_a).cross(pos_c - pos_a).normalize();
+
+        normal[a as usize] += norm;
+        normal[b as usize] += norm;
+        normal[c as usize] += norm;
+        normal_denom[a as usize] += 1;
+        normal_denom[b as usize] += 1;
+        normal_denom[c as usize] += 1;
+    }
+    for (denom, norm) in normal_denom.iter().zip(normal.iter_mut()) {
+        *norm /= *denom as f32;
+    }
+    normal
+}
+
+pub fn generate_tangents(index: &[[u32; 3]], position: &[Vec3], texcoord: &[Vec2]) -> Vec<Vec3> {
+    let mut tangent_denom = vec![0; position.len()];
+    let mut tangent = vec![Vec3::ZERO; position.len()];
+
+    for &[a, b, c] in index {
+        let (pos_a, uv_a) = (position[a as usize], texcoord[a as usize]);
+        let (pos_b, uv_b) = (position[b as usize], texcoord[b as usize]);
+        let (pos_c, uv_c) = (position[c as usize], texcoord[c as usize]);
+
+        let pd_ba = pos_b - pos_a;
+        let pd_ca = pos_c - pos_a;
+        let td_ba = uv_b - uv_a;
+        let td_ca = uv_c - uv_a;
+
+        let face_tangent =
+            (pd_ba * td_ca.y - pd_ca * td_ba.y) * (td_ba.x * td_ca.y - td_ba.y * td_ca.x);
+
+        tangent[a as usize] += face_tangent;
+        tangent[b as usize] += face_tangent;
+        tangent[c as usize] += face_tangent;
+        tangent_denom[a as usize] += 1;
+        tangent_denom[b as usize] += 1;
+        tangent_denom[c as usize] += 1;
+    }
+    for (denom, tang) in tangent_denom.iter().zip(tangent.iter_mut()) {
+        *tang /= *denom as f32;
+    }
+
+    tangent
+}
+
+pub fn generate_texcoords(index: &[[u32; 3]], position: &[Vec3]) -> Vec<Vec2> {
+    let _ = (index, position);
+    // TODO implement equirectangular projection or something
+    (0..position.len())
+        .map(|i| vec2(i as f32 * 0.01, 0.))
+        .collect()
+}