Refine color extraction in generate3d function for original mesh

- Enhanced the process of extracting per-vertex colors from the original mesh by utilizing tensor operations.
- Implemented a scaling adjustment to ensure color values are within the [0, 1] range.
- Improved overall clarity and performance of the color assignment workflow in the mesh generation process.

inference.py

@@ -63,7 +63,12 @@ def generate3d(model, rgb, ccm, device):
 
     from kiui.mesh_utils import clean_mesh
     orig_verts = data_config['verts'].squeeze().cpu().numpy()
-    orig_colors = ... # get the color for each original vertex, shape [N, 3]
+    # Extract per-vertex color for the original mesh
+    orig_verts_tensor = data_config['verts'].unsqueeze(0)  # shape [1, N, 3]
+    with torch.no_grad():
+        dec_verts = model.decoder(triplane_feature2, orig_verts_tensor)
+        orig_colors = model.rgbMlp(dec_verts).squeeze().detach().cpu().numpy()
+        orig_colors = (orig_colors * 0.5 + 0.5).clip(0, 1)  # scale to [0, 1]
     verts, faces = clean_mesh(
         orig_verts.astype(np.float32),
         data_config['faces'].squeeze().cpu().numpy().astype(np.int32),