받침 중심 정렬 + 부재별 색상 구분

bearing.rs: X 중심, Y 하방향 (-h to 0) 기하학 수정
bridge_scene.rs: 받침 X 오프셋 제거 (girder 정렬)
Mesh: colors 필드 추가 + recolor() 메서드
sweep.rs / occt.rs: 기본 콘크리트 색 자동 채움
bridge_scene: 부재별 색상 (거더/슬래브/받침/교대)
shader.wgsl: base_color 입력 → 조명 계산에 적용

선택(Selection) 기능은 계획대로 별도 Sprint에 구현.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cimery/crates/kernel/src/bearing.rs

@@ -7,12 +7,18 @@ pub fn build_bearing_mesh(ir: &BearingIR) -> Result<Mesh, KernelError> {
     if ir.plan_length <= 0.0 || ir.plan_width <= 0.0 || ir.total_height <= 0.0 {
         return Err(KernelError::InvalidInput("bearing dimensions must be positive".into()));
     }
-    // Centred box: plan_length × total_height × plan_width
-    // X = along span (plan_length), Y = height, Z = transverse (plan_width)
+    // Box: X=[-l/2, +l/2] centred, Y=[-h, 0] (top at Y=0 = girder soffit), Z=[0, w]
+    // Caller translates to girder X offset; Y=0 means bearing top sits at soffit.
     let l = ir.plan_length as f32;
     let h = ir.total_height as f32;
     let w = ir.plan_width as f32;
-    Ok(sweep::centred_box(-l/2.0, 0.0, l/2.0, h, w))
+    let profile = vec![
+        [-l * 0.5, -h ],
+        [ l * 0.5, -h ],
+        [ l * 0.5,  0.0],
+        [-l * 0.5,  0.0],
+    ];
+    Ok(sweep::sweep_profile_flat(&profile, w))
 }
 
 #[cfg(test)]

cimery/crates/kernel/src/lib.rs

@@ -39,6 +39,19 @@ pub struct Mesh {
     pub indices:  Vec<u32>,
     /// Per-vertex normals (unit vectors).
     pub normals:  Vec<[f32; 3]>,
+    /// Per-vertex base colour [R, G, B] in linear sRGB.
+    /// Default: concrete grey. Set by scene compositor per feature type.
+    pub colors:   Vec<[f32; 3]>,
+}
+
+/// Default concrete grey (PSC-I standard colour).
+pub const COLOR_CONCRETE: [f32; 3] = [0.80, 0.76, 0.65];
+
+impl Mesh {
+    /// Repaint all vertices with a single colour.
+    pub fn recolor(&mut self, c: [f32; 3]) {
+        self.colors = vec![c; self.vertices.len()];
+    }
 }
 
 impl Mesh {
@@ -127,7 +140,8 @@ impl GeomKernel for StubKernel {
             0, 1, 5,  0, 5, 4,  3, 7, 6,  3, 6, 2,
         ];
         let normals = vec![[0.0_f32, 1.0, 0.0]; vertices.len()];
-        Ok(Mesh { vertices, indices, normals })
+        let colors  = vec![COLOR_CONCRETE; vertices.len()];
+        Ok(Mesh { vertices, indices, normals, colors })
     }
 }
 

cimery/crates/kernel/src/occt.rs

@@ -141,7 +141,8 @@ mod inner {
             .map(|&i| i as u32)
             .collect();
 
-        Ok(Mesh { vertices, normals, indices })
+        let colors = vec![crate::COLOR_CONCRETE; vertices.len()];
+        Ok(Mesh { vertices, normals, indices, colors })
     }
 }
 

cimery/crates/kernel/src/sweep.rs

@@ -66,7 +66,8 @@ pub fn sweep_profile_flat(profile: &[[f32; 2]], span: f32) -> Mesh {
         push_tri(cen_b, [profile[i][0],profile[i][1],span], [profile[j][0],profile[j][1],span]);
     }
 
-    Mesh { vertices, normals, indices }
+    let colors = vec![crate::COLOR_CONCRETE; vertices.len()];
+    Mesh { vertices, normals, indices, colors }
 }
 
 // ─── Convenience shapes ───────────────────────────────────────────────────────
@@ -115,11 +116,13 @@ pub fn merge_meshes(meshes: Vec<Mesh>) -> Mesh {
     let mut vertices: Vec<[f32; 3]> = Vec::new();
     let mut normals:  Vec<[f32; 3]> = Vec::new();
     let mut indices:  Vec<u32>      = Vec::new();
+    let mut colors:   Vec<[f32; 3]> = Vec::new();
     for m in meshes {
         let base = vertices.len() as u32;
         vertices.extend_from_slice(&m.vertices);
         normals.extend_from_slice(&m.normals);
+        colors.extend_from_slice(&m.colors);
         indices.extend(m.indices.iter().map(|i| i + base));
     }
-    Mesh { vertices, normals, indices }
+    Mesh { vertices, normals, indices, colors }
 }