1 files changed, 64 insertions, 0 deletions
diff --git a/client/src/meshops.rs b/client/src/meshops.rs
new file mode 100644
index 0000000..e76e02a
--- /dev/null
+++ b/client/src/meshops.rs
@@ -0,0 +1,64 @@
+use glam::{Vec2, Vec3, Vec3A};
+
+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, tang) in normal_denom.iter().zip(normal.iter_mut()) {
+        *tang /= *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: &[Vec3A]) -> Vec<Vec2> {
+    let _ = (index, position);
+    // TODO implement equirectangular projection
+    todo!()
+}