"Smoothed Surface" does not Plot as Defined in the Layout/Paper Space

[MasonDCooke]

I am experiencing a contour plotting issue in Civil 3D when using a surface style with the "Smooth Surface" edit applied to it. The "Smooth Surface" was done using Natural Neighbor Smoothing, if that is applicable.

In paper space, the contours display correctly and are assigned to the expected contour layers. On my sheets I have two viewports, one with the contours plotted at their typical thickness and another with them screened. However, when plotted, the contour colors do not appear to follow the viewport layer color overrides. Instead, they plot using their original layer colors (see images below).

If I disable contour smoothing, the viewport layer color overrides plot correctly. The issue only occurs when the contours are displayed as smoothed contours.

Has anyone encountered this behavior before? Is there a setting related to smoothed contours, surface styles, or plotting that would cause contour colors to ignore viewport layer overrides?

I am using Civil 3D 2026 but was also able to replicate the issue on Civil 3D 2025.

Paper Space (Two Viewports with Different Layer Colors):

Plot with Smoothing:

Plot without Smoothing (Same Surface with Smoothing Toggled Off):

[SoaresASBCAD]

I was able to reproduce the same behavior in Civil 3D 2025 and 2026. It appears that contours generated with Natural Neighbor Smoothing do not honor viewport layer color overrides during plotting and instead use the original layer colors. Disabling contour smoothing restores the expected plotting behavior. This seems more like a Civil 3D limitation/bug than a style configuration issue. As a workaround, consider plotting with smoothing turned off or extracting the contours to polylines.