fix(gsplat): 2DGS image fit — expand colors to [1,N,3] for packed=False

app_gsplat.py

@@ -155,6 +155,10 @@ class SimpleImageFitter:
         quats_n = quats / quats.norm(dim=-1, keepdim=True)
         op = torch.sigmoid(opacities)
         colors = torch.sigmoid(rgbs)
+        # 2DGS packed=False: colors must be [..., C, N, D] to match projected means2d
+        # (same leading dims as viewmats batch). Plain [N, D] hits assert in rasterize_to_pixels_2dgs.
+        if rasterize_fnc.__name__ == "rasterization_2dgs" and colors.dim() == 2:
+            colors = colors.unsqueeze(0)
         out = rasterize_fnc(
             means,
             quats_n,