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I am trying to create an object of a building which has a sloped flat roof (I'm ok with that) but while the actual building is regular it has external sides which slope outwards at the top (see image below of actual building and note the (false) sides slope away from the building. I have created the false sides using extrude along normals successfully but cant work out how to 'drag' the top of the false side to result in a sloping front edge of the false side. I have tried selecting vertices and also edge using extrude along normals but I cannot get it to 'work'. Any help would be appreciated. I have also included an image of my Blender model. I feel that I probably need to separate the (extruded 'false') side I created but can't select it - I watched a video tutorial on separating and the author shows press L with the 'cursor' over the part required selects it (in edit mode) but that doesn't work for me. I will use extrude to normal to create a separate roof later. enter image description here

enter image description here

enter image description here

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    $\begingroup$ do you mean this? [1]: i.sstatic.net/80LYy.png $\endgroup$
    – Chris
    Jul 29, 2021 at 5:44
  • $\begingroup$ Yes that looks just like what I am trying to achieve $\endgroup$ Jul 29, 2021 at 5:49
  • $\begingroup$ I'm sorry my answer took a while, I wanted to make it as detailed as possible for you to follow along. In my solution you don't have to care for the location or rotating angles. If you have a house with a sloped roof anywhere in your scene, no matter which location or rotation, you can create the desired result. The thing is, it works with houses you already have- you don't have to build them new. $\endgroup$ Jul 29, 2021 at 7:38

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I would do it this way... This looks like a lot now, but I'll best explain every step with a screenshot. For this method it doesn't matter where your house is placed or how it's rotated.

Let's say you already have the house with a sloped roof and those "border faces" cut which I've selected in the first screenshot to show them (your screenshot looks like you have a model like that, too):

slope01

Now press Ctrl+R for the Loop Cut tool, move your mouse to the side until the cut is shown crosswise on the building. Left-click to confirm the cut direction.

slope02

After the first click, you can edge slide the cut towards the end where you want "false" side slopes. Get them close to the end, left-click once more to confirm the cut.

slope03

Now get rid of the large face at the side end of the house and also the small rim faces at the top and bottom. Select them (I showed it in Wireframe Mode to make them all visible). Hit X > Delete > Faces.

slope04

If you now select the outmost edge on the left or right of the new hole in the house, you can fill this hole by pressing F three times, this will create three faces from left to right (or the other way round if you selected the right edge). Now your house has to "rims" at the end which only need to be sloped in the right angle as the roof.

slope05

slope06

Select the top corner edges on the roof. To move vertices along an edge without changing the angle or direction of the edge (i.e. preserving the original slope angle), you can use Edge Slide. Enable it by pressing GG (that's a double G). Note that now you can only move towards the house or down the edges. To extend the edges beyond the existing mesh, you have to disable clamping. To do that, you hit C once (or keep pressing Alt). Very important: the direction of the edge that is going to be extended along is determined in the moment you press C or Alt, so make sure your mouse is somewhere above the middle of the top roof edge. The extension will be indicated by yellow lines going beyond the mesh. If it's the wrong direction, press C again or release Alt to enable clamping, then place the mouse differently and hit C another time to disable clamping again. Sounds more difficult than it is.

slope07

slope08

Now you can move the mouse until the "false" slope sides extend as much as needed. Then left-click or Return to confirm the new position and you're finished with the sides. To create a roof on top, go to the next steps.

slope09

For the roof we first have to create a face between the extended sides. Select the three inner edges and press F to make a new face.

slope10

Before you can extrude the roof, make sure that the new face is oriented correctly. Enable Face Orientation in the overlays. If the face is red instead of blue, select it (if not already), then use Alt+N > Flip.

slope11

When they are all blue, select the top faces and simply hit E to extrude them upwards. But be aware that this will (usually) extrude along the (averaged) face normal, which means it doesn't go straight up the Z axis, but angled in the direction of the slope (the average normal of all selected faces). To change that while extruding hit Z once and you can move freely, hit Z again and it will move upwards along the global Z axis. Pressing Z a third time will get you back to moving along the face normal.

slope12

To make the roof overlapping the building, you can select all faces along the border of the extruded roof, then press Alt+E > Extrude Along Face Normals.

slope13

The difference to the normal Extrude is, it extrudes along the different face normals respectively, so that the roof borders extend to the outside. You might experience strange angles on the corners like in the following screenshot:

slope14

If you like the corners like that, slightly rounded instead of sharp 90° angles, you're fine ;) To change them into sharp corners, hit S to turn on Even Thickness. And that's it. You can of course repeat the extruding actions to create another "layer" of roof on top of the one you have now.

slope15

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    $\begingroup$ You guys are great in showing that Blender can be used in many ways to achieve the same result. This result seems to have more steps in it but has educated me into more 'features' of Blender I have never used before such as Fill (create new face). There are so many 'tools' in Blender and maybe I have used about 10% of them so far. I have just used part of your method on my mode (as I had already created the angled front edges) to create and check a new Face and it was already blue. Something else I have learned - thanks. $\endgroup$ Jul 29, 2021 at 22:58
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    $\begingroup$ Gordon, I would love to tick the 'accept this answer' but in doing so this would 'untick' Chris' method which I used before your method was posted. I now have actually used BOTH your methods, Chris' method to create the angled front edges and your for nearly everything else. What should I do without upsetting Chris? $\endgroup$ Jul 30, 2021 at 0:08
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    $\begingroup$ Wtf Awesome dude $\endgroup$
    – BabyBoy
    Jul 30, 2021 at 5:39
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    $\begingroup$ @JohnArnold I guess that's a question only Chris could answer ;) You can only accept one answer here on BSE, so it's always the questioner's choice which answer he accepts. It doesn't matter what others might think to be the better solution, but as long as all answers are here everyone might pick the one that suits him best. And the many steps I put in the answer, well I know you are still learning as I'm reading a lot of your questions, so I thought it's good to show you some tools and not just rush by "easy" parts, assuming you can follow all steps without explanation. $\endgroup$ Jul 30, 2021 at 6:07
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Personally, I agree with @moonboots, that here, it could be much easier to start in the flat.

Just arrange a bunch of 2D shapes. They can be the same object, separate objects, whatever is easiest. It helps to have their Wireframe displayed.

The advantage is, you can adjust at this stage as much as you like, without side-effects propagating across a model.

Make sure, that somehow, all the shapes you will need to extrude later are in the combination, somewhere. You don't need vertices at the intersections of edges, that comes next.

enter image description here

Once happy, CtrlJ join the shapes into one object, X delete 'Faces Only', and Knife Project the lot down on to a clean plane:

enter image description here

Select out the faces you need, delete the rest, maybe tidy up some internal edges..

enter image description here

.. and then the rest is extruding selections of faces, deciding how far, and which faces, as you go along. A Mirror modifier means you only have to build one half.

enter image description here

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  • $\begingroup$ You guys are great in showing that Blender can be used in many ways to achieve the same result. $\endgroup$ Jul 29, 2021 at 22:42
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Another approach would be to create a twisted plane, cut 2 vertical edges with the knife (K to activate, C to cut orthogonally):

enter image description here

Then extrude once:

enter image description here

Then extrude again, mirror, etc:

enter image description here

Or extrude the face:

enter image description here

Tilt it with the Shear tool:

enter image description here

Cut with the knife, use W to cut through, snap it at the start of the edge to keep it on the right angle:

enter image description here

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  • $\begingroup$ Thanks Moonboots. Maybe a little more complex (for me) though $\endgroup$ Jul 29, 2021 at 7:29
  • $\begingroup$ the first solution I give is very easy actually $\endgroup$
    – moonboots
    Jul 29, 2021 at 7:31
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  1. add a loop cut of the thickness you want to have

enter image description here

  1. add another loopcut as near as possible to 1)

enter image description here

2b) make sure, your cube origin is 0,0,0 and your cube starts at 0

enter image description here

  1. select these 4 vertices

enter image description here

  1. with R Y you can rotate

enter image description here

  1. then with G X you can move it to the right place

enter image description here

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  • $\begingroup$ That looks great. NO wonder I couldn't work out how to do it since you use two cuts. I am guessing now that to create a roof it won't be a simple extrude over the whole top area and maybe only achievable adding another mesh cube on top? $\endgroup$ Jul 29, 2021 at 6:11
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    $\begingroup$ there are nearly always several possibilities. You could add a cube on top (maybe even with a boolean modifier to "union"). The "simple" extrude does not work if you do my solution first. If you first extrude your top, and then do my solution, it should work too. $\endgroup$
    – Chris
    Jul 29, 2021 at 6:14
  • $\begingroup$ Thanks again Chris. There also was some X Z also to get everything lined up $\endgroup$ Jul 29, 2021 at 7:30
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    $\begingroup$ @Chris Actually I don't care about those emails anymore... as you said, I'm so curious and permanently online. I even forgot I turned them on. Yeah, I checked this - as I said, I've set "Inbox" to "Daily". $\endgroup$ Jul 29, 2021 at 8:01
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    $\begingroup$ @Chris I guess you're right ;) $\endgroup$ Jul 30, 2021 at 6:09

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