Inspect a curved surface in wireframe
Choose a feature you can recognize
Open the sample in the viewer and locate the circular opening in the center. Follow the ridge from its lip down to the base of a blade. Keep that blade in view while you switch between solid shading and wireframe. Starting from a recognizable edge gives you a reference when many triangle outlines overlap.
Trace the outer contour
Rotate the rim until you see it against the dark background. A row of straight outline segments approximates the curve. Zooming in enlarges those segments, but it cannot introduce new ones. A straight diagonal inside a flat region is different: two triangles can occupy the same plane and still have a shared edge.
Compare a second export
If a curve looks too coarse, adjust the curve tolerance in your CAD exporter and save under a new filename. Take a PNG of the original outline first. Inspect the revised part from a similar distance and direction, then compare how much the silhouette changed relative to the increase in triangle count. Keep the file that preserves the features your next step needs.