2.8 Curve bevel and taper scaling issues I'm trying to design jewellery in mm scale so I have set my scene length to be millimetres. So far, mostly so good I think.

Importing and SVG is no longer in um scale - yay. I'm not quite sure of the scaling, but it imports a letter at about 18mm wide.

I create a belief circle with a radius of 1.5mm (I want a 3mm diameter wire)

I add this to as the bevel object to my letter and all good. But I want to scale the letter up. But it also seems to scale the application of the beizer circle as well. Hmm, lets tackle it a different way.

Wipe everything, import the SVG, scale the letter to the correct dimension, apply scale. Now the curve is showing the correct dimensions, and 1.00 as all the scales. I apply the same 3mm diameter wire I created above, but it has still doubled the wire diameter. Why?

Also, I want to center the letter, so I grab it and move it. The bit I cannot apply location changes to a 2D object? Why?

Ok, so I scaled the wire circle inversely proportionally to the scale I applied to the path. I'm in an OK place. Now I want to taper the object, but. I can not find a working example in the millimetre scale. 

If I create a regular bezier curve, and apply it to the taper of my letter. I get a tiny thin wire. So I know that deflection in the Y dictates the thickness along the taper, however I had assumed that the peak of the curve would be 100% of the full bevel.... but it doesn't. If I grab all the points and move them off the y=0 plane in edit more it gets a little thicker possibly... but I can put the peak at 100m and I still only seem to get a tiny line.

Even with a simple example, it does not work as expected. Is this a scaling bug as above?



Can anyone provide an example of how to make bevels and tapers work in the millimetre scale, or point me at what I'm doing wrong, or where my assumptions are wrong? I can provide a simple blender file if that helps anyone?

Thanks
Partial answer, in order to scale a beveled curve without scaling the beveled section/object,


Scale your curve,
Apply Scale then uncheck the Apply Properties of the Apply Object Transform




As far as Taper goes, it only influences the bevel profile in the X/Y space. I.e. if the taper curve has some Z dimension, it will be ignored.

The full X extent of the taper object applies proportionally (i.e. normalized to) to the full length of the tapered curve. In other words, if the taper object extends between x=-1.0 to x=+1.0 (relative to its origin): 


the Y coordinate at x=-1.0 will define the bevel profile width at the start of the parent/tapered curve and
the Y coordinate at x=+1.0 will define the bevel profile width at the end of the parent/tapered curve


The Y scaling is relative to 1m in the Y axis from the origin. Also a side effect is that scaling the taper object in the X axis will not change anything since the normalization to the parent curve length occurs.



If you want to control the exact dimension of the taper effect on the bevel profile in relation to your bevel object,  take the bevel dimension and calculate the scale factor required at the different taper positions along the parent curve and make sure that the Y coordinate of the corresponding taper control point has the right scale factor to obtain the desired value.

For example: with a bevel circle of 3mm radius if you want to obtain a bevel width of 5mm in the middle of the parent curve, make sure that the control point in the X center of the taper curve has a Y value of 5/3m from its origin in the Y axis