Dimensions

[Hidetoshi6721]

So I started making a model few months ago, and now it's mostly finished. I exported it, and the shape was TOO SMALL for the track. How do I figure out the correct dimensions for:
1. The spacing between the wheels for the model to fit on the track?
2. The height, length and width of the model?

P.S. I use Blender 2.93.

[superheatedsteam]

Check your Scene Properties>Unit System and Unit Scale.

Whichever system you use, metric or imperial, when in edit mode, select a vertex and see where it is located in the x, y and z co-ordinates. You build 1:1 in Blender. So if the real world object you are modelling is 4 metres tall and 22 metres long, then this is the size it should be built in Blender. The default box in Blender is 2m cube for example.

Blender_Units_Metric.jpg
Blender_Units_Imperial.jpg

It is also possible that during the construction of your model the scale has changed. Check that all the parts in your model have a Scale of 1 in the X, Y and Z co-ordinates. If not then use CTRL + A and select Scale to reset the scale back to 1. In the example below the scale is 5.848, it should be 1 before exporting.

Blender_Scale.jpg

[Hidetoshi6721]

Check your Scene Properties>Unit System and Unit Scale.

Whichever system you use, metric or imperial, when in edit mode, select a vertex and see where it is located in the x, y and z co-ordinates. You build 1:1 in Blender. So if the real world object you are modelling is 4 metres tall and 22 metres long, then this is the size it should be built in Blender. The default box in Blender is 2m cube for example.

Blender_Units_Metric.jpg
Blender_Units_Imperial.jpg

It is also possible that during the construction of your model the scale has changed. Check that all the parts in your model have a Scale of 1 in the X, Y and Z co-ordinates. If not then use CTRL + A and select Scale to reset the scale back to 1. In the example below the scale is 5.848, it should be 1 before exporting.

Blender_Scale.jpg

This was the exact answer I was looking for. Thank you

[Hidetoshi6721]

Just want to ask one more thing:
What are the best practices to accurately model a shape in accordance with real life dimensions? For instance, in my model described in the OP, I had to re-model some parts.

[superheatedsteam]

Unless you have dimensioned drawings from the manufacturer or better still, the ability to spend time physically on your subject with a camera, notepad and tape measure then the ability to model with 100% accuracy starts to diminish.

With my workflow, remodelling is normal for me. I don't know what best practice is but this is what I do.

I will try and get a line drawing from a reliable source with some dimensions. The red box in the image below is to the overall height, length, and width of the locomotive in the plans. I import the image of the plans as an empty and scale the empty so the locomotive length on the plans is the same as the length of the red box. Now the plan is as close to 1:1 scale as I can make it, I make copies of that plan for the top and end views. I can now start to model the shape of the model using the plans as a guide to get the proportions correct. If the wheels are 42” in diameter I model them at 42”, not to the size on the plan as I work on the assumption that there are inaccuracies in the plan.

blender_90class.jpg

Often photos will show details that the plans do not. I will also import photographs as an empty and scale those to known dimensions on the model (in wire frame view) to use as a reference for adding detail fine tuning proportions. You have to bear in mind that photos often have perspective distortion so account has to be made for that. Sometimes I perform perspective correction of a photo in a 2D graphics program before importing into Blender as a reference.

If the primary dimensions of my model are correct and the rest of the model appears in proportion then that is good enough for me.

I make models to the best of my abilities for a open source rail simulator with the skills and references I have at the time.

[pwillard]

I've always made sure that I have some known dimensions before I start. So no matter what size I accidently made something, once I have the true dimensions of a shape... I make sure my model matches those dimensions... not some drawing I don't trust.