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I'm back with another super basic question.

I have four faces that I want to extrude inward(or outward) ten grid units. So I have done the following...

enter image description here

I want to snap the faces in or out and have them snap to each grid line, but no matter what options I check, the extrude won't line up with the grid.

enter image description here

These two pictures are snapped to -.9 and -1, but they don't line up with the grid

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  • $\begingroup$ Are you really interested in snapping alone or is there some final 3D mesh you are creating? Snapping to grid is not the only way to snap and position. $\endgroup$ – atomicbezierslinger Sep 4 '15 at 0:26
  • $\begingroup$ It would also be useful for you to show your edit mode selection settings and snap settings as in the picture below in a proposed answer $\endgroup$ – atomicbezierslinger Sep 4 '15 at 0:49
  • $\begingroup$ I have been building boxes with a 3d printer to hold some electronics prototypes I have been working on. The box is going to be in five pieces. The faceplates, the top and bottom walls, and the back panel for port holes. The tolerances are important for fitting pieces together and for sizing button and port holes. I have my grid units representing millimeters and the stl's I have exported have worked perfectly in the printer. Now I am just trying to tighten up pieces. P.S. I don't want to use a CAD program because I want to get back into character modeling once I get the hang of Blender. $\endgroup$ – tantangula Sep 4 '15 at 11:44
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  1. Set the pivot to "active element" and the transform orientation to "normal"
  2. Select all four faces in Edit Mode.
  3. Once they are selected, hit Alt+E and select "region (vertex normals)"
  4. While the tool is active, hold Shift (to move in smaller increments) and Alt (to turn on even thickness), now it's possible to offset the faces in a predictable way

It moves two units each step instead of just one, but it's a workable solution. Also adjust the extrude settings to offset by just one unit:

enter image description here

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  • $\begingroup$ Please consider that this site is not a forum. If you are interested, here is the meta about the key markup: meta.blender.stackexchange.com/questions/524/… $\endgroup$ – p2or Sep 4 '15 at 11:46
  • $\begingroup$ I am interested in how you did that. Thanks! $\endgroup$ – tantangula Sep 4 '15 at 11:47
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Unfortunately this is mathematically impossible.


The simple explanation:

Shen scaling, snapping (by holding Ctrl) does not use the grid. You are basically multiplying an object's size, not incrementing (moving) it. So when snapping is enabled it snaps the scale factor to multiples of 0.1 (or 0.01 when Shift is pressed).


The mathematical explanation:

The biggest mathematical difference between scaling and translating (moving) is that when scaling an object, you aren't simply moving vertices a certain distance, you are multiplying the vertices' distance from a point (the pivot center) by a scale factor. So the larger the object, the smaller the scale factor would have to be to enlarge the object by one unit.

Example, if you have an object 1 unit x 1 unit it would take a scale factor of 2 to enlarge the object by 1 unit (in each direction); but if your object was 100 units x 100 units it would only take a scale factor of 1.01 to enlarge the object by 1 unit. So to make scaling snap to the grid Blender would have to dynamically adjust the scale factor the more you scale the object.

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  • $\begingroup$ I'm not scaling. I am trying to move each face a fixed distance along its normal. $\endgroup$ – tantangula Sep 4 '15 at 11:22
  • $\begingroup$ @tantangula I believe that extruding along vertex normals is actually scaling, the pivot point just varies per face. $\endgroup$ – PGmath Sep 4 '15 at 13:57
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enter image description here

Consider

  • Go into edit mode with edge selection and grab a single edge and snap it left right up or down

  • Move the 3d cursor to the desired location and snap to cursor.

  • Scale the extrusion by some fraction such as .2 (typed as number) (2 divided by 10 )

  • Create a large rectangle and use loop cut to subdivide. That feature can do even divisions of an edge.

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