I started using Blender about 6 months ago. I am fairly skilled with texturing, lighting, compositing, etc…

I really suck at modeling though. This is mainly because I can’t figure out how to use dimensions and constraints to make models.

I am used to CAD software, where you make a box, and then go and tell it that you want it to be 2m tall, 1m wide, and 3m long. I can’t figure out how to do this in Blender.

How can I make models actually adhere to specific dimensions? How do I use dimensions the way you do in Solidworks or Autodesk, or is this even possible?

If it’s not possible, how in the world do you people create realistic models?

3D view properties region (N) has dimensions in object mode. Set the dimensions and then ctrl+A -> scale to apply that.


My problem is that, for instance, adding a plane, I only get a “radius” value… I wasn’t aware that planes had radii… I thought they had width and length… I understand that I can use the “scale” values in the Properties > Object panel, but how am I supposed to take a standard of 2m which converts to 78.7402 inches, and scale that with scale values. If I want 100 inches, I shouldn’t have to know or have to calculate the scale of 1.269999 required in order to produce the 100 inches.

What if I want a 5x5x5 cube, with a 2x2x4 hole in the cube, offset on the x-axis by 1?
What if I have 2 separate objects that need to be X distance away from eachother, and then another object that needs to be 2.5X away?

There’s no way I’m gonna spend that much time fiddling with rulers, moving things by hand, using trial and error to get things as precise as they need to be.

To clarify what I mean, here is a picture:

Notice they were able to accurately position each part of the sketch with dimensions, and they can easily go back and change those values.

I just don’t understand how people can model things accurately without knowing the dimensions of complex models

Changing the units from metric to imperial is quite easy:

You can also type the numbers you want in different units and blender will do the conversion for you.

will turn into:

I am having similar challenges when trying to model with dimensions. This is mainly because earlier I have been modeling with Google Sketchup. It is hard to accept that you are not able to model with exact dimensions. Or maybe it is possible to do that but it will be quite complicated. Anyway, I liked the comments that JA12 had about precision in the other thread.

One Addon that I would be happy to pay for would be a Sketchup like Construction Line Addon in Blender. I think that it is one of the best functionalities in Sketchup (http://help.sketchup.com/en/article/95005). You can easily solve challenges with positioning like:

  •      Place hole center 50cm from the edge A and 30cm from the edge B
  •      Extrude Object A’s face to certain point which is 70cm from the Object B’s edge
  •      Etc. 

Hopefully somebody makes an Addon like that in some stage, even a paid one.

I already know how to do that. This isn’t what I’m trying to figure out

tristan401, very negative attitude man. People are trying to help you. If you’re having so much trouble getting Blender to do what you want t to do, then stop using it. buy Sketchup, Maya, Max , AutoCAD or some other modelling program. The guys here offering advice are trying to help you, even though you haven’t really said what you are trying to achieve.

I am sorry, I wasn’t intending to sound negative. I’ll try and explain a little more.

When I am in Blender, for example, I go to create a 3m X 4m plane. The default is 2m X 2m.
In the “Add plane” options, I only see an option for “radius”, which I assume is both the X and Y lengths.
In the properties panel, I don’t see any options for dimensions at all.

So here are my questions:

  • How do I create objects with specific dimensions (i.e. A 2m X 3m plane) without having to “eyeball” the dimensions
  • If I can’t do that, how can I create objects with accurate measurements?

Again I am really sorry that I came off as having a negative attitude. That was never intended. I love you guys

Here are some practices that may be applicable:

  • Entering dimensions in the Transform panel of the Properties region (N) as has already been suggested.
  • Entering exact 3D cursor position in the 3D Cursor panel of the Properties region.
  • Using snapping (to grid increments, to features - vertices, faces).
  • Entering exact numeric values for transformations (grab, rotate, scale, etc.).
  • Using operator options after applying the operator (bottom of the Toolshelf or F6 hotkey).
  • Using appropriate pivot points for rotations and scaling (e.g. 3D cursor or Active Element).
  • Using Manipulate Center Points setting to rotate or move objects relative to given pivot.
  • Using some align addon or another.
  • Using specific edit mode tools such as spin and warp.
  • Using different transform orientations, including custom ones.
  • Using aligned view.
  • Using settings in Mesh Display panel of the Properties region to see lengths and angles.
  • Realizing that Blender is not a CAD and many things cannot be done the way CADs do it.

Those are some good suggestions. I’ll be sure to try them.

It is kind of disappointing to know that you can’t create Blener models with accurate measurments though. That would be pretty useful.
Thanks for the help