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### Suggestion: ability to mix absolute and relative coordinates

Posted: Wed Aug 14, 2019 3:42 pm
I have recently discovered QCAD which I really like.

However, I do have one suggestion that I believe will improve the software's useability - at least for me. That is to be able to mix one relative and one absolute coordinate when specifying a target point.

At present the software allows the specification of two absolute cordinates in the form of 'x,y' or two relative coordinates in the form of '@x,y'.
Sadly there appears to be no immediate way to mix them - that is to specify the first coordinate as an absolute value and the second, as a relative value or vice versa.

For example I would like to be able to specify a point whose absolute x-coordinate is '3000' and whose relative y-coordinate is '0'. This would be useful when creating a line or when moving or copying an entity to an absolute point horizontally, but a relative point vertically.

The existing method of using the '@' symbol could be made to work in this scenario if the syntax allowed one to specify for example: '3000,@0' to mean 'x = absolute 3000' and 'y = relative 0'. However, this would become contradictory if the input was reversed to: '@0,3000' which presently means that both of the specified coordinates are relative, not only the x-coordinate.

Perhaps to save changing the ,meaning of the existing well-known syntax, an additional prefix symbol could be added to mean 'relative', such as the '\$' symbol. In this scheme, '\$0,3000' would specify: 'x = relative 0' and 'y = absolute 3000' (not both as relative). And, '0,\$3000' would specify: 'x = absolute 0' and 'y = relative 3000'. Although not needed in this convention, '\$0,\$3000' would specify: 'x = relative 0' and 'y = relative 3000', directly analogous to the existing '@0,3000'.

Perhaps this could be taken a step further by enabling the mixing of absolute and relative coordinates within arithmetical expressions. Although I cannot think of an immediate practical use, perhaps a syntax like: '100+\$10,\$20+130' could be legally evaluated.

What do other users think? Maybe I have missed a method of specifying this concept in some other way.
Best, Steve.

### Re: Suggestion: ability to mix absolute and relative coordinates

Posted: Wed Aug 14, 2019 5:52 pm
Did you try to move the relative zero and use?
And the restictions to that.
Depenpending on the case it's a powerfull setup.

Regards

### Re: Suggestion: ability to mix absolute and relative coordinates

Posted: Thu Aug 15, 2019 3:27 pm
Thank you, CVH. Indeed that is one way. However, this means that two steps must be taken instead of one.

Note however that the RZ command is unfortunately a little lacking in versatility. The RZ command awaits a click on a location to snap to an intersection or snap point to set the relative zero point.

However, if I want the relative zero to be at a position which is not at an intersection or grid point, there seems to be no numerical way to specify it. Thus, no way to specify coordinates to precisely set the relative zero point manually to any non-snapped, but specified, location. Of course one could first set a point using for example SP, but that is yet another step!

In such case it would then be really useful if the RZ command could expanded so that one could optionally specify either absolute or relative coordinates to which the relative zero should be set. For example, by invoking a command such as "RZ 250,300" - absolute - or "RZ @0,250" - relative (or as I would also like, using mixed absolute and relative coordinates eg "RZ 250,\$0" = absolute x = 250 and y = relative 0 ... no vertical movement, only horizontal) to move relative zero to the specified new location. Clearly such a command should position the relative zero point precisely without invoking any snap.

Of couse, I am relatovely new to QCAD, so I could be missing some tricks. On the other hand perhaps a new broom is less encumbered with old ideas!!

### Re: Suggestion: ability to mix absolute and relative coordinates

Posted: Thu Aug 15, 2019 6:00 pm
steve_appleton wrote:
Thu Aug 15, 2019 3:27 pm

Note however that the RZ command is unfortunately a little lacking in versatility. The RZ command awaits a click on a location to snap to an intersection or snap point to set the relative zero point.
Nope - that isn't correct.
steve_appleton wrote:
Thu Aug 15, 2019 3:27 pm
. Thus, no way to specify coordinates to precisely set the relative zero point manually to any non-snapped, but specified, location.
RZ accepts every kind of snap plus numeric inputs like:

Absolute Cartesian Coordinate,
Absolute Polar Coordinate,
Relative Cartesian Coordinate,
and Relative Polar Coordinate,

........ I would call that: Very versatile.

### Re: Suggestion: ability to mix absolute and relative coordinates

Posted: Thu Aug 15, 2019 6:23 pm
Very versatile indeed, Husky, I agry fully.

For some it might take some time to learn how to use it fully.
It may seem counterintuitive at start but that is probably old school doctrine.
There is nothing wrong with it, it's a mindset.

In very rare cases the auto placement of the relativ is off.
Beter, not as you would have hoped it to be.
Then you have to ask yourself how Qcad should have guessed what you wanted to do with it.

I can only advise steve_appleton to give it a try and use it in a nifty way.

Regards

### Re: Suggestion: ability to mix absolute and relative coordinates

Posted: Fri Aug 16, 2019 12:40 pm
A big thank you for pointing this out to me, Husky and CVH. I had not realised this was possible.

Unlike some other commands, for example LI and MV, the command "RZ" <enter> does not bring a prompt for a location or coordinates. The response is simply "Command: rz" The command line remains as "Command:". I had tried using the RZ command in one line with this syntax: "RZ x,y" (eg "RZ 0,0" <enter>) which brings the response "Invalid coodinate or distance" so I assumed it was not possible to specify coordinates.

Following your suggestion, I now realise that although no prompt is issued for a location or point, entering coordinates after entering the command achieves the result I wanted, thus: command: "RZ", <enter> and then command: "x,y", <enter>.

The user reference manual (https://qcad.org/doc/qcad/latest/reference/en/) does not mention this possible syntax under "snap, set relative zero". My suggestion is that after issuing the RZ command, the command line should prompt to click a location or enter coordinates.

Of course still remaining is the question of being able to mix absolute and relative cartesian or polar coordinates, my original suggestion.

### Re: Suggestion: ability to mix absolute and relative coordinates

Posted: Fri Aug 16, 2019 5:13 pm
steve_appleton wrote:
Fri Aug 16, 2019 12:40 pm
Unlike some other commands, for example LI and MV, the command "RZ" <enter> does not bring a prompt for a location or coordinates. The response is simply "Command: rz" The command line remains as "Command:".
Correct. If you need something is asking you for the position then you should make the Status Bar visible. You can find it below Menu/View ...

Husky-2019.08.16-01.png (5.35 KiB) Viewed 3917 times

steve_appleton wrote:
Fri Aug 16, 2019 12:40 pm

Of course still remaining is the question of being able to mix absolute and relative cartesian or polar coordinates, my original suggestion.
Where is the need to mix them? If I launch e.g. the line tool it will expect a single information for the first and a single information for the second point. If I like or need to determine the first point as a relative and the second point as a absolute coordinate then QCAD has no problems to deal with it ...

### Re: Suggestion: ability to mix absolute and relative coordinates

Posted: Fri Aug 16, 2019 5:40 pm
Fix the relative cartesian for X, choose any absolute for Y
Fix the relative cartesian for Y, choose any absolute for X

And Sorry, I can't figure out how to mix Relative or Absolute for X/Y and Polars for the second.