How do I create this 3D half-pipe look

Question

How can I create the blue half-pipe part?

I have already recreated the middle stack pieces via Effects > 3D > Extrude and Bevel. I am trying a similar concept for the half one but am having difficulty.

Answer 1

You can create a circle and a second one in the middle (the inner circle should be the size of the stacked ones)

Then draw a line down the middle and use Shape Builder Tool to separate them:

Rotate the (yellow) piece to desired angle and then apply the same 3D angles - just make the Extrusion Depth much higher:

Answer 2

From a rectangle with rounded corners, add Revolve effect:

Answer 3

You cannot make the parts separately, they must be made side by side. Otherwise matching them to fit is a nightmare.

As already shown, the needed buttons and the vertical curved wall (=pipe) are all possible to do separately as 3D revolutions or extrusions in Illustrator. Extrusion omits the roundings, setting a bevel do not fix it.

There are few difficulties:

1. The viewing angles can be complex to set. If you cannot calculate them or copy from somewhere, you must search the angles by trial and error. Extrusion is quite intuitive, but revolution isn't.

2. All parts have their own coordinate systems. Same wieving angles fortunately are good in this case, but the parts must be moved to fit. That must be done by eye.

3. Generated images are flat. You cannot place grey buttons inside the blue pipe. You must expand the appearance of the pipe, remove the clipping mask, ungroup several times and finally rise the needed splinters to top. There are plenty of them.

4. Placing the texts as mapped art in the 3D effect dialog is sometimes complex because the surfaces are often splintered. Just in this case it's easy, because all surfaces with texts are single pieces

See the image:

1. The shapes to be revolved. Grey buttons need rectangles, 2 corners rounded and all of them are united. The pipe needs a rounded rectangle. The small rectangle at the bottom is for the revolution axis. It's grouped with the big blue rectangle.

2. Revolution is applied to both shapes. Blue got 135 degrees, grey 360 degrees. Viewing angles are default.

3. Proper viewing angles are set. I saw them in another answer.

4. Grey buttons are made transparent. That makes possible to move them to the visually right place.

At this point the lights should be adjusted. It's impossible later. I skipped it. The lights are default.

5. The blue pipe is expanded, the clipping mask is removed, several ungroupings is applied and part of the blue splinters are raised to top to cover the grey buttons.

6.-7. A random text is dragged to the symbols collection. For visibility against white it's orange here. Art mapping subdialog in 3D revolution dialog is launched and the text is placed onto one grey surface. NOTE: In the appearance panel you can reopen effect dialogs for tweaks as long as they are not expanded.

This method to place texts would be difficult on the blue pipe, because it should be done before expanding its appearance. If it had been done, the text must be raised also to top at the same time when a part of the pipe was raised to cover the grey buttons.

Texts can be placed on expanded parts by skewing, scaling,rotating and warping as usually in 2D work.

There's still much details not done. The shadows (=partially transparent blurred black shapes) must be added manually.

For reference I tried the same in a simple freeware 3D CAD. Everything went more smoothly and at least four times faster than in Illustrator. Unfortunately from simple CAD the result isn't available as 2D vector image with colors and shading. The only 2D vector output is wireframe. Colors and shading output in 2D is a low resolution bitmap. Also lights and shadows are very poor when compared to full pro level 3D software. But it's free. See some screenshots:

BTW. The used free CAD = DesignSpark Mechanical, a heavily decimated version of SpaceClaim