Windows and Portal Techniques

[Sphynx]

One of the most simple operations to perform in 3D modelling is also one of those that seem to cause the most people consternation. As a result, here are various methods to create windows and portals in objects.

As I use more methods in my daily work, I may add them to this tutorial if I feel that they are significantly different and not just variations on a theme.

The bulk of this tutorial has been taken from one of the unpublished Blender for the Faint Hearted tutorials that I've not had time to finish. The tutorial is however, mostly about principles, so while this is a Blender tutorial it should have some benefits for other 3D application users are well.

[Sphynx]

This method utilises the old Blender philosophy of 'modeling around holes'. It assumes that you are not cutting a hole in an object, but instead can build the 'wall' from scratch - as such, it doesn't answer many peoples questions, so bear with me. For now, we'll assume a window aligned perfectly along an axis.

1. Build your hole. For this method, I've just used a 32 sided circle primitive.
2. I've selected all of the points and selected a local pivot with the [,] key so that the pivot point is in the centre of the selected points.
3. Using extrude [e], hitting [esc] then [s] I get a second set of points that I can scale. I scale them to about 110% of the original size.
4. I grab four of the points at the corners and drag (or numerically place them) at the corners of the wall in which the window lies.
5. I select all of the redundant points in the outer circle and merge them with the four corners.
6. I manually fill in any holes by selecting points and hitting [f] to create new polygons.
7. A completed wall with a hole in it.

[Sphynx]

This is the second most simple method of creating a window or portal in a wall. Again, we are talking about regular shapes, so we can use the built in tools in most cases to make our cuts.

1. I start with a wall and added a second object in the form of another 32 sided circle to represent where we want the hole to be. If everything was perfectly aligned, we could just join the two objects then select points to create into polygons, so we are going to assume that we don't want this - I've rotated the circle a little so that our hole is going to be an ellipse, not a perfect circle.
2. To get a reasonable object that we want as a window, I've selected all of the points of the circle and hit [shift-f] to generate a surface within the circle. We do this as we want to extrude along the circle's normal - we do this next by hitting [e] and extruding the region to get a cylinder (you could just generate a cylinder from the start, but this is teaching skills ).
3. I position the cylinder so that intersects the wall were I want the elliptical window to be.
4. I select the cylinder then the wall, then press [w] to reveal the boolean cutting options. I select [Intersect] so that the cylinder cuts a depression into the wall surface. This should leave a new (unselected) mesh with the depression, with the wall and cylinder still selected. I don't need these now, so I can move them to another layer for safety, or just delete them using [del].
5. Selecting then editing the new mesh, use vertex mode to select all of the back ring.
6. These vertices are not required, so I delete them. As we are deleting the vertices, the lining polygons back to the wall can't exist and so delete as well.
7. At this point, there is nothing more that I need to do - these are simple objects, so the intersection was quite a good operation and the only 'clean-up' that was needed was to delete those back vertices. Depending upon the nature of the wall and portal, you may need to perform more clean-up.

[Sphynx]

cont. (five image attachment limit)

[Sphynx]

1. Using the last technique, I create a wall with a number of faces and a less regular shaped portal that I want to cut into the wall - in this case, an airlock.
2. I repeat the technique to cut the hole in the wall - as can be seen, the boolean operation was this time less than 100% 'neat', but that's fine. The goldern rule in this is that we want points, not polygons.
3. A cleaned up mesh, with some points joined together, and the original polygon arrangement modified to my liking, not Blenders.
4. I select the inside rim of the hole and extrude outward (I don't need to create a face across the hole for this one, as I can extrude along a normal axis) to create a door rim, then again to get some door depth.
5. I select two of the perfect opposing points of a half-circle to establish the centre for scaling this side of the door (so that the circle scales smoothly), and put the cursor at that point. I then select the points that make up that curve of the door and scale to 90%.
6. I repeat the process with the other half of the door, then separately with the two centre points as they were not part of either circle. I now have an angled recess in the door, giving the impression of bulk.
7. I repeat the process of extruding and scaling demonstrated over the last few sections to create a recess in the front of the door.
8. Now all we need are some details to give the door some life.

[Sphynx]

cont.

Next sections:
Regular portals in curved walls
Curved portals in curved walls

[Shadowman99]

Very nice. I have some reaction control thrusters I working on for a viper, so I'll give your workflow a go.

Do you have a blender-friendly hull plating method? Especially one that works on rounded surfaces.