In the picture are the plane I want to merge.
My plane generation method is to make the upper and lower planes first, and then use the edges of the upper and lower planes to generate the intermediate planes and then merge, but the result is failed.
I have tried to change the uv direction and the result is useless
Where did I go wrong?
The bottom surface is bad. It must have been created with an input curve with too many control points towards the ends. I created a section between the XZ plane and your bottom surface then tried to extend the curve on both ends and the extensions go backwards. You need to delete some of the control points or rebuild the curve and extrude your base surface again. That’s what I did for the bottom.
Similar situation for the top surface. I untrimmed the top surface and trimmed it with the interpolated curve created with your 499 division points. Like this, the boundary of the top surface coincides with the edge of the loft.
I internalized the geometry in the edited definition, hence no Rhino file attached.
Thank you Martin Siegrist for solving the big trouble for me, I spent a lot of time in this part.