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Placing points relative to others

Posted: Mon Oct 15, 2012 12:37 am
by luggw1
This may be a difficult question to get across, but I'm going to try just the same. Understand that I come from the background of Bentley Microstation, so it colors the capabilities that I'm looking for in QCad. What I'm looking to be able to do is snap to a point, say an intersection of two lines, and then specify a relative distance from that point to place the first point of a new entity. Is this possible in QCad? I understand that I could create a temporary entity, like a line, to work from, but I've found that sometimes that can get a little messy if the construction lines get away from you.

Thanks.
Bill Lugg

Re: Placing points relative to others

Posted: Mon Oct 15, 2012 10:15 am
by andrew
This can be done in QCAD using relative coordinates.

There is a snap tool that lets you specify a relative coordinate in the tool bat at the top. Relative coordinates relate to the last used point in the drawing, marked with a small red cross and a circle.

You can also enter relative coordinates in the command line using the syntax @x,y, for example:
@10,0
for the point that is 10 units to the right of the last used point.

Other coordinate types are:

Absolute coordinate:
x,y

Absolute polar coordinate:
distance<angle

Relative polar coordinate:
@distance<angle

Re: Placing points relative to others

Posted: Mon Oct 15, 2012 8:45 pm
by Clive
luggw1 wrote:What I'm looking to be able to do is snap to a point, say an intersection of two lines, and then specify a relative distance from that point to place the first point of a new entity.

Based on QCAD 3
In addition, you can make good use of the ' Set Relative Zero' option from the Snap tool-set.

using - Set Relative Zero (1).png
using - Set Relative Zero (1).png (45.24 KiB) Viewed 11688 times


For example if we set our new relative zero point at an intersection, we can now draw new entities (lines, circles etc.) with starting points 'relative' from this new 0,0 'relative' coordinate.

using - Set Relative Zero (2).png
using - Set Relative Zero (2).png (45.76 KiB) Viewed 11688 times


In this example I am drawing a circle with a radius of 10. After choosing the circle option (Center, Radius cr), I am presented with snap options.
The snap option I am using is 'Coordinate' (sx).

using - Set Relative Zero (3).png
using - Set Relative Zero (3).png (67.51 KiB) Viewed 11688 times




This snap option presents X and Y coordinate input fields (in the top tool-bar) for either 'absolute' or 'relative' coordinates, in this case my starting point (center of circle) is relative to the last position I set (Relative Zero).
* Note -you must 'Tick' the relative field input box!

using - Set Relative Zero (4).png
using - Set Relative Zero (4).png (56.05 KiB) Viewed 11688 times


* Once you have specified your first point for example with a line - click on the green tick to set this point.
To exit this snap option (coordinate sx) you can either click on the Restrictions Off (+) snap button or on the Auto (SA) snap button.

Re: Placing points relative to others

Posted: Tue Oct 16, 2012 2:15 am
by luggw1
Thanks, I think that's exactly what I'm looking for. I'll have to play with it to better understand how it works.

Bill Lugg