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I'm new to Blender, and am building a flat surface to be extruded later (submarine deck).

I've designed an outline as a Bézier curve which I then converted to mesh. After that, I iteratively created the slots in the deck in the same manner. For convenience, I have placed the slots into groups, as you see, tagged with suffix numbers from 0 going left to right (stern to bow). Groups 0, 1, and 4 have been successfully integrated.

I join a group of slots to the outline, go to edit mode, and apply fill, and it works fine, as you see: enter image description here

However, I seem to hit a brick wall at this point. When I try to add new slots (in this example, group numbered with suffix 2), the fill seems to break. I've tried different groups and even just tried to add single slots, to see whether one of them is somehow improperly designed, but I can't get past this point: enter image description here

Is it likely something about the individual slot construction? They were all built from the same template, just adjusted in length....

Note: not sure whether it matters (like in fonts) but the outside outline was a clockwise curve, the two hatches (not joined here) are counterclockwise, and the slots were created using the circle curve feature and not altered.

EDIT: following suggestions below, I was able to achieve near-complete success (all but four slots of several hundred), as follows:

  1. Build a clean main object.
    • extrude my outline to deeper than needed.
    • create a 'plank' from a cube, making it longer and wider than needed, but correct height.
    • select plank and apply boolean modifier 'intersection' using the outline. Plank and outline modifier overlay
  2. For a given group of slots, create and apply a boolean 'difference' modifier in a similar fashion. Deck with a group of slot difference modifiers
    • in a few cases, some fiddling about was required such as making groups smaller, doing them in a different order, or using 'face' rather than 'fill' before extruding the modifiers (though in most cases it made no difference).
  3. End result: enter image description here
    • note: after each application of a difference modifier group, I checked carefully for quirks in solid mode then examined the mesh in detail in wireframe mode; if I saw anything out of the ordinary I backed up and tried something else.
  4. Ultimately, I was able to produce what I wanted and a clean (as far as I can see) topography, except for 4 slots where the boolean differences failed no matter what I did. I understand that these can be fussy, and I tried every trick I could find on the internet with no luck. But I think the last four can be done perhaps at the wireframe level (?) and can open another topic for that.
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    $\begingroup$ You can't create hole inside a surface without an edge connecting a vertex of this hole to the border of your surface. So I guess at one point this must have messed up your surface. With this kind of object it would be very easy to create a grid of quads and extrude down for example. Also, if you don't want any close-up, you could simulate those slots with Bump or Normal nodes, it would make your object much lighter... $\endgroup$ – moonboots Apr 27 '20 at 16:05
  • $\begingroup$ Unfortunately I don't understand a word of what you said :( $\endgroup$ – K.G. Feuerherm Apr 27 '20 at 16:35
  • $\begingroup$ so maybe begin with some basic tutorials about modeling ;) $\endgroup$ – moonboots Apr 27 '20 at 16:37
  • $\begingroup$ I am working on it. I tried this after doing the 2.8 tutorial where a 2D curve is converted to mesh and then extruded. And it worked just fine for this, as you see, until a certain point.... $\endgroup$ – K.G. Feuerherm Apr 27 '20 at 16:41
  • $\begingroup$ Grant Habbit have made some nice beginner tutorials, you should check: youtube.com/user/mediagabbitt/videos $\endgroup$ – moonboots Apr 27 '20 at 17:00
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Here are several ways to do a series of slots on a surface:

Beginning with the grid:

  • Create a plane, subdivide it:

enter image description here

  • Extrude its border, round it with an AltShiftS (or give the outer shape you want).

enter image description here

  • Select the faces you want and extrude down.

enter image description here

  • Continue to work on the shape.

enter image description here

Knife Project:

  • Create your surface object.

enter image description here

  • Create a plane, subdivide itd.

enter image description here

  • Delete the faces only.

enter image description here

  • Put your grid object above the surface object. Select the grid then shift select the surface object, then go in Edit mode. Then in the header menu choose Mesh > Knife Project.

enter image description here

  • The operation has cut the grid on the surface. As you can see and as I explained, if you cut a shape within a shape, you necessarily have an edge connecting the inner shape with the outer border.

enter image description here

  • Bring some correction so that your surface has a proper topology, i.e. edges that connect to the border edge and quads rather than tris or ngons if possible. Use the join tool (J) to join vertices. Create vertices on the border edge if necessary.

enter image description here

  • select the faces you want and extrude down.

enter image description here

  • Continue to work your object.

enter image description here

Arrays and Boolean:

  • Create an array of cubes with 2 Array modifiers.

enter image description here

  • Apply the Array modifiers. Delete the cube you want.

enter image description here

  • Bring your submarine object, give it a Boolean modifier with the cubes object as Object.

enter image description here

  • Apply the Boolean modifier, bring some corrections to have a clean topology.

enter image description here

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  • $\begingroup$ Thanks for this, it gives me some ideas of technique in general, though it won't be nearly that simple: the slots are not rectangular and they are also not really evenly spaced except by regions. If I can make the slots the shape I need (circular ends with rectangular mid-section) then I should be able to apply one of these techniques on a reduced area, and repeat as required. BTW the tutorials you pointed me to are excellent, they will go a long way! $\endgroup$ – K.G. Feuerherm Apr 28 '20 at 12:23
  • $\begingroup$ yes maybe begin with a lot of beginner tutorials, it will help later to find the best method for each object you'll build. $\endgroup$ – moonboots Apr 28 '20 at 12:25
  • $\begingroup$ I think the last technique may be the best: I already made all the slot shapes, so if I use the deck outline and extrude to 3D, then take each group of slots and extrude to 3D and use in succession as boolean modifier that may work. But I'll do more tutorials first so that the rationale is clearer to me with regards to the topology and connecting to the outside. $\endgroup$ – K.G. Feuerherm Apr 28 '20 at 12:52
  • $\begingroup$ note that for the last solution I didn't finish the topology, it needed to be work to get cleaner ;) this last solution is not necessary the best because there might be more rework, as the topology is a bit messed up... and try to work with quads, sometimes triangles if necessary... ngons (faces with more than 4 vertices) are ok on flat surfaces, not so good otherwise. $\endgroup$ – moonboots Apr 28 '20 at 13:09
  • $\begingroup$ I have had good success so far starting with a cube made into a plank and then using boolean difference modifiers to cut holes. Works 99% of the time; occasionally seems to do something weird. I'll have to look into that tomorrow. $\endgroup$ – K.G. Feuerherm Apr 29 '20 at 1:43

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