For this next stage, we will build the "contour" or the "outline", I called in French: La fin de pièce

All Class A surface know for this kind of part we need to manage this contour of the door trim according to the seal flange of the BIW (Body In White).

This is vital to understand that ALL class A work need to be adjusted by the technical advice and input... That is what I called CLASS A, when we build only the shape with a scan data refrence, it is for me the A SURFACE work... "A" for visual shape, styling shape...

Hope it is clear for you, because I saw / see / will see many mistakes or missunderstood between this two different jobs... Many people spoke about "Class A" but do only "A surface"... There are also many discutions and forum about this two aspect of our job but at the end we need to build first the A surface and if all engineering / process / marketing / styling requests are respected we can spoke about Class A...
Also for me it was "impossible" to build Class A if the 3D modeller have not enough knowledge about A surfacing skill.

Also for our case, I will build a quick surfaces arround the door panel according ONLY by the scan data I got.

First I build one simple surface (we can start by a plane one) and increase the number of CV's to cut the outline door mesh like that:

The transparent green surface is the surface I will use for cutting my mesh... This is my workflow to use the transparent shader for all surfaces I used for cutting and I used also a 100% transparent shade for surfaces help me to build something, I will show you later probably.

After that we need just to rebuild the outline intersection between the mesh and the green surface...

Try to keep the minimum of CV's (control points) for your curves, same as I said before, it will be possible to increase the number any time... But it will be pratically impossible to reduce later (or more difficult).

At the moment I have 1 curve degree 1, 2 curves degree 3 and 2 curves degree 5.

This degree 5 curve cause by the G2 (curvature continuity).

After that we need to build a Draft surfaces according to these lines. For these draft we need to "copy" the scan data, but we need for Class A to check the minimum angle requested in case the 3D physical model do not reach this value. For the plastic part usually the engineer used 3° minimum but there is one "funny" workflow for me in the class A area... When the engineer asked for 3° minimum, all surfacers build 3,1° or 3,2° draft angle to make sure when the engineering department check their data all are correct!

Because when the engineer check it is only BLACK and WHITE no grey!

Means if they check and the angle of 3° is not correct (not green when they check) they said WRONG... if we check carefully you can have a minimum angle egal to 2,99° but it is WRONG ! ! ! Funny no.

I used a draft with 8° angle to match approximatly to our model.

Again, as you see I like to build my first surfaces the most big as I can but try to keep the size of your surfaces according to the shapes. Means I did not like the solid software who build some infiny surfaces when they are using plane and / or fillet... At the end all control points will be inside the bounding box of your model (it is not a Class A request but just a workflow)...

Now we have the top surface, the outliner... Next step later soon!