[solved] Restrict Angle & On Entity

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Russell Ault
Newbie Member
Posts: 7
Joined: Wed Oct 28, 2020 3:09 am

[solved] Restrict Angle & On Entity

Post by Russell Ault » Wed Oct 28, 2020 3:21 am

Hi there!

Windows 10, QCAD Pro 3.25.2

I'm still learning QCAD, so it's entirely possible I'm just doing something wrong, but I'm not getting the behaviour I'm expecting and I'm wondering if it's me or of it's something else.

I'm trying to draw a line with a defined start point, a defined angle, and an end point at the intersection with a second line. Rather than drawing a line of arbitrary length and then trimming/extending it to the second line, I had hoped that I could use the "Line from 2 Points" tool with "Restrict Angle" set to the defined angle and snaps set to "On Entity". In my mind, this should give me exactly what I'm looking for: a line starting at a defined point and proceeding at a specified angle until it snaps to the second line (and therefore ends at the intersection).

Unfortunately I'm finding that this doesn't actually work. While the cursor appears to be snapping to the second line, it doesn't actually snap, and moving the mouse around allows creating a line that is slightly longer or shorter than the intersection. Am I doing something wrong?

Thanks!

-Russ
Last edited by Russell Ault on Wed Oct 28, 2020 9:15 pm, edited 1 time in total.

CVH
Premier Member
Posts: 1004
Joined: Wed Sep 27, 2017 4:17 pm
Location: Belgium; Antwerp

Re: Restrict Angle & On Entity

Post by CVH » Wed Oct 28, 2020 6:29 am

Hi Russ,
yes and no ...

Correct, once you define a startpoint and an angle the intersection spot with any entity out there is a fixed point.
In the old days we placed our ruler in an angle over the startpoint and drew up to the other entity.
The ruler would be our preview in CAD.

But it doesn't work out because QCAD doesn't predict where those intersections of the preview and all the rest would be.

The CAD way:
Draw a line from a startpoint LI+EL or LA+adequate length so that it crosses your destination entity.
Now a real intersection exists.

The first option is to trim ... :roll:
(= old school eraser)

The second:
Select the line.
Pick up the endpoint and place it on the actual intersection. :wink:
(= rubber band)

Regards,
CVH
QCADpro 3.25.2.1 / win7pro 32 bit / 4GB / 1e generation i7 2.6Ghz / HDD GeForce GT 520

Russell Ault
Newbie Member
Posts: 7
Joined: Wed Oct 28, 2020 3:09 am

Re: Restrict Angle & On Entity

Post by Russell Ault » Wed Oct 28, 2020 6:53 am

CVH wrote:
Wed Oct 28, 2020 6:29 am
[...]
Correct, once you define a startpoint and an angle the intersection spot with any entity out there is a fixed point.
In the old days we placed our ruler in an angle over the startpoint and drew up to the other entity.
The ruler would be our preview in CAD.

But it doesn't work out because QCAD doesn't predict where those intersections of the preview and all the rest would be.
[...]
Huh, I think I find that a bit confusing: if I don't set a pre-determined angle then QCAD has no trouble producing an intersection-based endpoint with the "On Entity" snap, so why can't it do it when an angle is set? Shouldn't that make the prediction easier?
CVH wrote:
Wed Oct 28, 2020 6:29 am
[...]
The CAD way:
Draw a line from a startpoint LI+EL or LA+adequate length so that it crosses your destination entity.
Now a real intersection exists.

The first option is to trim ... :roll:
(= old school eraser)

The second:
Select the line.
Pick up the endpoint and place it on the actual intersection. :wink:
(= rubber band)
This is what I have been doing; I was just hoping for something faster. :)

Thanks!

-Russ

CVH
Premier Member
Posts: 1004
Joined: Wed Sep 27, 2017 4:17 pm
Location: Belgium; Antwerp

Re: Restrict Angle & On Entity

Post by CVH » Wed Oct 28, 2020 8:06 am

Russell Ault wrote:
Wed Oct 28, 2020 6:53 am
Huh, I think I find that a bit confusing:
You are right about the fact that for your case all newly intersections with the world all matematically exist perfectly.
Only QCAD doesn't predict those future intersections.

Not one, the nearest to the cursor, nor any.
In a complex drawing your angled preview would cross hundreds or more entities.
At that point snapping on an entity is making thing worse ...

Snapping on means your cursor snaps to be on the entity.
If you do that in the open one would see that the angled preview runs untill orthogonal to the cursor.

Mix those two and you get an entity that is just to short or just to long.
One can not place the cursor in pixels so it would be exact in vectors.
Russell Ault wrote:
Wed Oct 28, 2020 6:53 am
if I don't set a pre-determined angle then QCAD has no trouble producing an intersection-based endpoint
Your counter example is somewhat different.
The angle is free, so the endpoint with snapping on an entity is a point on the target entity orthogonal to the cursor.
It wouldn't be possible to pinpoint that exact point in pixels.
Hold your cursor as far away from the target as QCAD will allow you to and see that again this is not intersection-based.

The fastest way would be a brain interface ... :wink:

Regards,
CVH
QCADpro 3.25.2.1 / win7pro 32 bit / 4GB / 1e generation i7 2.6Ghz / HDD GeForce GT 520

Russell Ault
Newbie Member
Posts: 7
Joined: Wed Oct 28, 2020 3:09 am

Re: Restrict Angle & On Entity

Post by Russell Ault » Wed Oct 28, 2020 9:15 pm

CVH wrote:
Wed Oct 28, 2020 8:06 am
[...]
Snapping on means your cursor snaps to be on the entity.
If you do that in the open one would see that the angled preview runs untill orthogonal to the cursor.
[...]
Ah okay; I was picturing "On Entity" as being intersection-prediction-based (like "Perpendicular" or "Tangent") as opposed to an orthogonal approximation, but with your explanation I can see why this couldn't possibly be correct.

Part of my confusion is that I'm also learning AutoCAD right now (learning two different CAD platforms at once must be good for brain elasticity, right?), and when drawing angle-restricted lines it will predict an intersection with the object nearest the cursor and snap to it, but that's just a special kind of "Intersection" snap and has nothing to do with "On Entity".

So maybe I'll put in a feature request for something like that (a "Predict Intersections" checkbox in the "Restrict Angle or Length" toolbar?), but you've definitely answered my question: yes, I was doing something wrong based on not understanding the tools. :)

Thanks for your help!

-Russ

Updated to add: I did put in a feature request, which I think might be more generally useful than what I was contemplating here.

CVH
Premier Member
Posts: 1004
Joined: Wed Sep 27, 2017 4:17 pm
Location: Belgium; Antwerp

Re: [solved] Restrict Angle & On Entity

Post by CVH » Sat Oct 31, 2020 6:17 am

Voted for it
Regards,
CVH
QCADpro 3.25.2.1 / win7pro 32 bit / 4GB / 1e generation i7 2.6Ghz / HDD GeForce GT 520

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