first commit

src/scene/pipeline/mesh_gpu.rs

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+// Mesh GPU buffers — TriangleList rendering for solid objects.
+//
+// Vertex layout (40 bytes):
+//   position   [f32; 3]   offset  0   12 B
+//   normal     [f32; 3]   offset 12   12 B
+//   color      [f32; 4]   offset 24   16 B
+//                                ------
+//                                 40 B / vertex
+
+use crate::scene::mesh_model::MeshModel;
+use iced::wgpu;
+use iced::wgpu::util::DeviceExt;
+
+// ── Vertex layout ─────────────────────────────────────────────────────────
+
+#[repr(C)]
+#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct MeshVertex {
+    pub position: [f32; 3],
+    pub normal: [f32; 3],
+    pub color: [f32; 4],
+}
+
+impl MeshVertex {
+    pub fn layout<'a>() -> wgpu::VertexBufferLayout<'a> {
+        wgpu::VertexBufferLayout {
+            array_stride: std::mem::size_of::<MeshVertex>() as u64,
+            step_mode: wgpu::VertexStepMode::Vertex,
+            attributes: &[
+                wgpu::VertexAttribute {
+                    offset: 0,
+                    shader_location: 0,
+                    format: wgpu::VertexFormat::Float32x3,
+                },
+                wgpu::VertexAttribute {
+                    offset: 12,
+                    shader_location: 1,
+                    format: wgpu::VertexFormat::Float32x3,
+                },
+                wgpu::VertexAttribute {
+                    offset: 24,
+                    shader_location: 2,
+                    format: wgpu::VertexFormat::Float32x4,
+                },
+            ],
+        }
+    }
+}
+
+// ── GPU handle ────────────────────────────────────────────────────────────
+
+pub struct MeshGpu {
+    pub vertex_buffer: wgpu::Buffer,
+    pub index_buffer: wgpu::Buffer,
+    pub index_count: u32,
+}
+
+impl MeshGpu {
+    pub fn new(device: &wgpu::Device, mesh: &MeshModel) -> Self {
+        let has_normals = mesh.normals.len() == mesh.verts.len();
+        let vertices: Vec<MeshVertex> = mesh
+            .verts
+            .iter()
+            .enumerate()
+            .map(|(i, &pos)| {
+                let normal = if has_normals {
+                    mesh.normals[i]
+                } else {
+                    [0.0, 1.0, 0.0]
+                };
+                MeshVertex {
+                    position: pos,
+                    normal,
+                    color: mesh.color,
+                }
+            })
+            .collect();
+
+        let vertex_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+            label: Some(&format!("mesh.vbuf.{}", mesh.name)),
+            contents: bytemuck::cast_slice(&vertices),
+            usage: wgpu::BufferUsages::VERTEX,
+        });
+
+        let index_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+            label: Some(&format!("mesh.ibuf.{}", mesh.name)),
+            contents: bytemuck::cast_slice(&mesh.indices),
+            usage: wgpu::BufferUsages::INDEX,
+        });
+
+        Self {
+            vertex_buffer,
+            index_buffer,
+            index_count: mesh.indices.len() as u32,
+        }
+    }
+}