Confusing values for Z axis in sketches

[alexGGJUW]

I've "default modeling orientation" set to "Z up". When I try to make a sketch in either XZ or YZ planes, surprisingly positive values for Z axis go down (below XY plane), instead of up. However, if I have a sketch in XY plane, and extrude it for a positive value, the extrusion is made upwards as expected. This feels contradictory....

E.g. in the screenshot of a sketch below, I'd expect positive Z values to go up, not down. The reason I noticed this was that I created CSV file with point coordinates for spline. I was surprised that the shape after import was upside down (values for Z in the file were positive).

Is this normal? Do I have something misconfigured? If this is normal... Why is a choice of Z axis pointing downwards instead of upwards normal?

[jeff_strater]

see this post for an explanation:  why-is-my-sketch-text-appearing-upside-down 

[jhackney1972]

@jeff_strater, Just a heads up, your referenced link is not valid.

[g-andresen]

Hi,

Switch off the grid and use only the dimensions and constraints as a guide to your design requirements.

günther

[jeff_strater]

thanks, @jhackney1972 .  Not sure what happened.  Trying again:  why-is-my-sketch-text-appearing-upside-down 

[alexGGJUW]

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@g-andresen wrote:

Switch off the grid and use only the dimensions and constraints as a guide to your design requirements.

I'd love to be able to do that, and simply use constraints to get the path to be where it needs to be. That is how I'd normally do things. But. The problem is that I'm importing points for a spline from a file. The shape (and/or positions of a points on that shape) can not be geometrically constructed. The shape can only be calculated via non-trivial mathematical formula (see the formula for Haack Series nose cone here https://en.wikipedia.org/wiki/Nose_cone_design#Haack_series). The coordinates of each point are absolute re sketch's coordinate space. AFAICT, once I import coordinates of points (from a CSV file), I can only apply constraints on individual points of the spline, which constrains only that one point distorting the shape of the path. I don't see how I could do either of these in a sketch:

• Apply a constraint on one point of a spline, and have all the other points move with it (thus translating/rotating spline path itself).
• Group those points and/or fix them relative to each other. I can only fix their absolute positions (via Fix constraint), but if I do that, other constraints (such as dimensions or coincidence) can't be applied to it anymore, since spline is now fixed in place.
• Apply constraints on a spline itself. It'd seem they are always applied to individual control point of a spline.