Precise Object Placement problem?

[Anonymous]

I've been using ArchiCAD for a few months now and have noticed some strange behaviour when placing objects on a plan.

For example, when placing a door, if I move my cursor over a snap point (e.g. the end of a wall) and use numeric placement to move the cursor 1350mm in X I find that the door looks as if it is in the right place. If I move my cursor over the door edge (tick cursor showing) the delta X shows 1350mm (which is correct). However, if I dimension the distance from the door to the wall end it ends up at 1350.5mm!

If I turn on snap (to snap grid - grid at 50mm) and position the door 'by hand' and dimension as above then all is well!

What am I doing wrong?

[Anonymous]

I don't understand precisely what you are doing from your description. It sounds as if you are moving the User Origin (little black x) to the corner with shift + opt/alt and then placing the door by typing in the distance in the coordinates palette. This should produce precise results, so I wonder if you are doing something a little differently.

In any case it sounds like your preferences are set to display more accuracy in dimensions than in working units (coordinates palette).

[Anonymous]

Mathew,

I've tried making use of the 'user origin' as well as just relying on object 'hotspots' (e.g corner or edge of wall) and I get the same behaviour.

I'd be happy to 'hide' this problem by reducing the accuracy displayed by the dimension but I'm worried that these might be 'real' errors that will build up in my model and cause later problems. Also, on occasions I've seen discrepancies that are whole millimetres (but that might have been finger trouble!).

[Anonymous]

I'm still not sure what you are doing wrong. The numeric entry method will produce consistently accurate results. It may be possible that you are placing relative to one element and dimensioning to another that is slightly off the first. Perhaps the wall isn't exactly horizontal?

You are right to want to maintain the accuracy of the model. Slight errors can accumulate into serious problems.

[Anonymous]

Sometimes if you do not zoom right in when selecting a point with the tick method you might accidently go off the tick when performing the left click. This can be corrected through Options, Preferences, Mouse Contraints and Methods, Cursor Snap Range - Increase the amount of pixels to say 7 or 8. This means that as you click on the tick if you slide off the tick if you are within 7 or 8 pixels away it will still select that point you want. Sometimes people try to increase accuracy by decreasing this value which actually causes more accuracy problems. Note that even 7 pixels is less then 1mm. If only we were as accurate as ArchiCAD is...