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  1. #1

    Cutting a hole in a CYLINDER

    I'm trying to cut a circular window into the side of a cylinder. I've tried doing it using the RETOPO tool but to no avail - it just looked a mess when I filled it
    Can anyone give me any advice on how to do this or maybe a link to a vtm or something?
    Thanks

    Adam



  2. #2
    Check out this thread: http://blenderartists.org/forum/showthread.php?t=110443

    As you can see I was running into quite the same problem. The advice was really good and worked like a charm.

    I didn't finish the project though. Maybe another time



  3. #3
    Thanks 13Bullets, what I'm trying to do though is cut a circular hole in a cylinder. I don't think the method in the thread you linked me to is suitable is it?



  4. #4
    Yes, I was hoping the advice there might help you. Try adding a circle each on the bottom and at the top (they will make the walls of a makeshift "cylinder") and one for the hole. Connect edges top to bottom and around the hole. Add loop cuts so you can attach the "walls" (spanning from top to bottom) to the hole.

    This is from the top of my hat, can't come up with a smarter solution right now.



  5. #5
    Member g60's Avatar
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    Is this what you are looking for? Let me know, here or PM, and I will write a quickie tutorial. There is some distortion around the hole but I might be able to do a cleaner job when I repeat the steps in a tutorial.

    Meanwhile, I will try to remember how I did it.
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  6. #6
    Yeah that's the kind of thing I mean ...I get distortion modelling it though. If I'm gonna be specific, I'm trying to model the central section of Mr Spoon's rocket.



    He needs it so he can see Blanket Sky on his way to Button Moon to spy on people through his telescope....

    EDIT - Thanks for the offer g60



  7. #7
    Okay, I tried the approach I've described earlier. I didn't use two circles for top and bottom though but took a 16-sided cylinder. I then added a 8-sided circle and started cutting loops into the cylinder so the verts of the circle were matched with those on loops. See attachment 1. Those were merged and the inside faces were deleted. Some faces had to be rebuild, then I threw 2 levels of subsurf onto the cylinder and there was the circular hole.
    Doesn't look particular pretty though and might yield the same deformations you mentioned. This might even be the same way you modeled your rocket
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  8. #8
    Member g60's Avatar
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    I like your approach. It looks good at subsurf level 2 and is pretty straightforward. I did it differently and mine has the disadvantage of being somewhat more complicated. It has a cool technique to get the circle into the cylinder.

    The base cylinder has 32 vertices. I have hidden the back half and the first image shows the selection of the forward-most edge. I have snapped the cursor (SHIFT-S Cursor->Selection) to the front of the cylinder to prep for the addition of a circle.

    Tab to object mode and create the circle. I think I chose a circle with 20 vertices but that was arbitrary. Scale it to fit the approximate location. Edit the cylinder to delete the cylinder faces where the circle will fit. Tab to object mode and join the circle and cylinder objects (CTRL-J).

    Now the fun part. Get the cursor back to the origin of the cylinder. I did this by selecting the 4 side vertices of the cylinder and snapping the cursor to them. One more step to make the subsurf'd hole look better later: from the front view, extrude the circle a small amount. Select only the circle of faces. From the top view, use the warp tool (SHIFT-W) to bend the circle onto the cylinder shape. The tool will allow you to place it with a reasonable margin inside the delete cylinder area.

    The hard work is done. Extrude the top edges of the circle up and use a knife (Knife Exact) to cut them even with the top edge. I've also cut a horizontal edge across the middle of the cylinder to help face the side vertices on the circle. CTRL-N to recalculate normals to the outside, then extrude the entire object outwards (select all vertices, extrude, escape, ALT-S to extrude out along the normals.)

    The final shows a subsurf level 2 plus smooth on the object. The warp tool is a cool thing.
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  9. #9
    Member Carrozza's Avatar
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    I would just add the use of Retopo tool to the methods already explained.
    1) create cylinder and circle
    2) project the circle on the cylinder with retopo
    3) delete and re-create faces lying under the circle.

    A a side note I learned a new valuable trick: g60 little extrusion of the circle before re-constructing the cylinder. Good idea, g60!



  10. #10
    Thanks for the input everyone - I'm trying to use the warp tool now as I'm not sure how retopo works but the warp tool distorts it in the wrong direction but I'll keep at it. Thanks.



  11. #11
    You can also use the knife subdivide tool to cut the holes.
    Attached Images Attached Images  



  12. #12
    Member Star Weaver's Avatar
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    Originally Posted by g60 View Post
    Now the fun part. Get the cursor back to the origin of the cylinder. I did this by selecting the 4 side vertices of the cylinder and snapping the cursor to them.
    In your example, you could also go back to object mode and snap the cursor, which will go to the object center, useful if you haven't moved the object's general shape off axis-center in the relevant ways.

    Your thing works for finding any center tho .
    Brown leaves around the,
    Well, in the clearing. Of thinking,
    Grace is only felt.



  13. #13
    Member pappy's Avatar
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    Listen to Carrozza.

    A few refinements I learned on a recent project that needed lots of holes in a long shaped tube. ( Saxophone )

    1. Snap cursor to a selected face in the center of where your hole will go.
    2. Use a 2 window layout in "view" mode.
    3. One window use "view from above" view. (shift-v) This will put the view to directly above the selected spot.
    4. Other window set to "view from side or front" view. (shift-v) - DO NOT CHANGE THESE ORIENTATIONS UNTIL THE HOLE IS DONE.
    5. Set pivot to 3d cursor.
    6. Look at where the hole will go and plan how many vertices your mesh circle (next step) will need to be cleanly attached. If necessary use the loop cut tool now to add additional vertices to the area the hole will be in. If you do this now your mesh will stay smooth. It's still possible after you delete the faces, but requires careful use of the knife tool.
    7. In the "view from above" window add your circle with the number of vertices you have decided are needed. (don't worry about getting it right the first time, if need be you can always delete and replace the circle.) If you are in "face" mode switch to vertex or edge.
    8. In the "side/front" view window raise the circle until it is above the surface where the hole will be.
    9. Back in the "top" window scale and rotate the circle to both be the correct size and to line up with existing vertices as well as possible. (if at this point you find that you used too few/many vertices, repeat the previous few steps (delete the existing circle)
    10. Now separate the mesh circle from the body mesh, and leave edit mode.
    11. Select the separated circle object and go into edit mode. Switch to shaded view if not already on.
    12. Click the Retopo button to enter Retopo mode, click "Retopo All" and mouse click in the TOP view window. The circle will "snap" down onto the main body.
    13. Click the Retopo button to turn off Retopo mode.
    14. Tab out of edit mode.
    15. With the circle object still selected, shift select the body object and "ctrl"-J join meshes.
    16. Tab back into edit mode and switch to face select. Delete the faces underlying the circle.
    17. Create faces to fill the gap from the circle to the body object. DO NOT move the vertices that make up the hole.
    18. Loop select the inner edge of the hole and extrude it (in or out - your choice)
    19. Apply subsurf
    20. Loop cut and slide to harden the "join" between the surfaces.

    Takes about 5 minutes after you've done it two or three times.

    Pappy
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    Last edited by pappy; 18-Mar-08 at 03:43.



  14. #14
    Thanks pappy! Worked a treat



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