How to do a Long Sweeping Curve?

[FriedCheese]

Fairly new to 3D modelling in general. I've created a few boxes, but nothing too fancy. 

I'm trying to model a backplate for a smart home sensor. The issue I'm running into is that the outer edges have a long sweeping curve and I have no idea how to re-create it besides using a fit point spline and doing my best to follow the curve and then copying it to the other corners. That works, but I just feel like there's a better way. Using fillet is pretty close, but not quite there.

Thanks for any help!

[g-andresen]

Hi,

what do you want to achieve?

something like that?

günther

[FriedCheese]

No. I know how to do an offset, the problem is the existing edges in the body do not follow the contours of the actual backplate. See here where the existing body outline is compared to the spline I drew to match the contour.

[jeffescott]

Try less fixed points.  Use control handles to adjust shape.  
minimizing fixed points reduces constraints required and allows algorithm to converge to a smooth curve

[FriedCheese]

I was hoping there's a better way to do this other than to just free hand it. When using the spline method, I ended up with some very minuscule bump outs where the points would meet.

I was only using the spline points to define a single curve and then mirroring that across the axis for the others. Maybe I should try just setting the points around the entire perimeter instead.

[jeffescott]

Maybe say a point at each corner maybe on on each side at the high point

shape might be a little off but smooth and shapely

[etfrench]

Use a control point spline.  Constrain and dimension the control points to keep all four quadrants equal:

Note: There are extra points showing at the top and bottom.  Use the side points.

[Warmingup1953]

X,Y Dimensions via Vernier or digital callipers?

[davebYYPCU]

No contour in the file I downloaded, 

add 2 point spline, and make tangent handles tangent to the box, adjust their length until perfect.

Extrude the quadrant, mirror the body, twice.

Might help.....

[TrippyLighting · Accepted solution]

The best way to capture the shape isn't a photo although I've used that as well in a pinch.

I would use a very sharp pencil and trace the shape on paper and then scan the shape.

I would use that scanned image as the canvas and then scale the canvas to match measurements taken with a caliper.

As the shape looks to be mirror symmetric across the horizontal and vertical axis, only 1/4 of the outline has to be sketches using a single control point spline. I used a single-span 4-degree control point spline (5 control points) in the attached design with the proper constraints. That means that the construction lines that connect the control points are horizontal/vertical. As there is another symmetry across the red axis (dash dotted line) , there is an equal constraint on two of the construction lines (red circles). That recreates the shape well enough!

If more precision is desired I'd add another control point and re-apply constraints and adjust the control points as needed to better match the shape.

These objects are usually designed by industrial designers using best practices in that line of work. That means single-span splines with the lowest degree (lease amount of control points) needed to represent a given shape.

Model is attached

[FriedCheese]

Using the control spline with constraints was it. I knew there was a proper way to do this without a thousand control points.

I'll keep the trace part in mind, but this plate has a bunch of fins on the back so I ended up with a super wavy line. Agreed that the photo isn't the most ideal (except manufacturer photos seem to be more solid). I can make sure I'm level, but not that it's parallel.

Thanks for the guidance!