How do I snap to two points or push together objects

[mathcubes]

Hello guys, like what the title says how do I snap to two points or is there collision detection to push objects together without gaps in Qcad? And if not then what is the best way to go about it?
To give you a gasp on what I am trying to do. Here are the some examples but read them in order

1st example, in this screenshot now I inserted some squares at various angles and tried to line them up. For the first role that was simple but for the second. I can get them to perfectly touch one but not the other. I guess the workaround would be to resist the movement to one angle of the line in which it touch to align it up to the other.



2nd example, lets say I want to do the same thing with circles…. I have no clue what work around would be.


3rd example, between these two circles lets say I needed a line with a length of two, now mathematically a place should exist. Now, I can align it to one but I can not align unless I move it but than that would of course throw off the first point. Perhaps if it was a slight lines there would be a simple mathematical formula I could use.



I draw up designs which they resembles diagrams which also require I get it correct. Simply if I was drawing on it on a sheet of paper I could just simply cut out the shapes and push them together. It’s should logically be easy to do and is quite intuitive but I have no idea on how to actually do it.

Any ideas?

---

Background to this, I just downloaded Qcad a few hours and I couldn't figure it out. I come form Adobe Illustrator but it has a weird quirk where nothing is precise. For example, you can have a 2 what-ever-unit square then make it 100x scale then for some reason it's 200.38 or something like that. I deal with modular design some of which can be complex and I make everything precise but then it doesn't align up with each other or like you can get it on a 45 degree angle and some of the intersecting paths would than go slightly pass it or before or its slightly screws up the angle which throws off the modular design. I know other vector editing programs do not have the problem with scale like Affinity Designer but I never test it with alignment. I was just told it was due to how the back-end works with vector that there is nothing I can do about it as everything is just highly approximated. Hints on why I want to switch because I actually want to have the ability to have it scale and as close to perfect as reasonable.

[CVH]

mathcubes,

Hi and welcome to the forum.
QCAD is vector based and that would be as precise as possible and scaled just the same.
On how precise that is and on how certain a number in 64 bit floating point really is we can write a book or two.
For instance, the value 0.1000... can't be expressed exactly in floating point but it will be very very close to 0.1 in binary.
But that will never induce an error in the region of 0.19% like your Adobe Illustrator example.


I have to admit I needed to read your topic more than twice to get a glimpse of what you're at.
There is nothing as collision detection implemented in QCAD.
To start with, nothing in line-art or even hatched 'solid' is considered as a solid.
For that you need a high-end (expensive) parametric application that works with solid shapes.

For the circle problem I think it is easy.
A circle with a certain radius touching two other circles can be drawn with Draw .. Circle .. Two Tangents and Radius (CTR).
And for two circles that are 2 units apart the distance between the centers is 2R+2 or R1+R2+2 with unequal radii.
Or meaning that center 2 would lie on a circle with radius R1+2 around center 1 and vice versa.
The intersection of 2 construction circles will give you none, one or two exact solutions.
The same goes for touching what is zero units apart.

In your circle example there are some places where one should roll over another until it touches a third circle.
Rolling is keeping the center distance steady ... A construction circle radius = R1+R2.
Touching is again a certain center distance ... A second construction circle radius = R2+R3.
Where they intersect you can place circle 2 its center.

Or you could draw a CTR circle tangent to a circle and a construction circle that is 2 units wider than the other intended.

That should be perfect when measured up although it may display incorrect at extreme high zoom.
The reason here is that curved lines are displayed interpolated ... segmented.
At a certain zoom state touching curved shapes seems to drift apart, but they still touch mathematical.

For the squares it is less simple.
Just because they have corners sticking out.
Again this requires construction lines and QCAD has several tool for that.
But here we talk about sliding a corner along a face (= line) until another corner meets another face.
I would solve this by a parallel of the face trough the other corner with Draw .. Line .. Parallel (trough Point) (LG).
Then it is a question of moving the shape from one reference to another with Modify .. Move/Copy (MV)
Select the square to move, type MV, not copy or delete original, from point A to point B.

mathcubesProblem.png (6.08 KiB) Viewed 6481 times

And of course, every problem will have several unique solutions and several ways to solve them.
Rotating a square around a corner so another corner meets a face requires a construction circle around the corner trough the second corner.
Then you can rotate the shape around the corner so the the other corner is where the circle meets the face.
Hint: In that case you define the angles with the mouse cursor (not by value), that is the pointer button beside the angle field in the dialog.

Rather curious in what math is done on the cubes (... mathcubes)

Regards,
CVH

[Husky]

1st example, in this screenshot now I inserted some squares at various angles and tried to line them up. For the first role that was simple but for the second. I can get them to perfectly touch one but not the other. I guess the workaround would be to resist the movement to one angle of the line in which it touch to align it up to the other.

You are correct. Use a Construction circle to find the perfect snap point for rotation. Something like this example video ...

Rotate rectangle.gif (1.23 MiB) Viewed 6463 times

... or for just a parallel move within an other rectangle this will do it:

slide rectangle.gif (1.1 MiB) Viewed 6463 times

2nd example, lets say I want to do the same thing with circles…. I have no clue what work around would be.

The circle tools should cover that. Please check those tools below Draw/Circle

Husky-2023.02.24-02.png (5 KiB) Viewed 6463 times

3rd example, between these two circles lets say I needed a line with a length of two, now mathematically a place should exist. Now, I can align it to one but I can not align unless I move it but than that would of course throw off the first point. Perhaps if it was a slight lines there would be a simple mathematical formula I could use.

If I understand this correctly then a construction circle can help you again. The first point is fixed and you can snap to the one or two other points to keep the line to two units.

2 mm connection.gif (1.07 MiB) Viewed 6463 times

If it need to be perpendicular to one circle rotate the 2 unit line again with help of an circle ...

Rotate 2 mm.gif (1.19 MiB) Viewed 6463 times

I come form Adobe Illustrator but it has a weird quirk where nothing is precise. For example, you can have a 2 what-ever-unit square then make it 100x scale then for some reason it's 200.38 or something like that.

There is a reason why it is called "Illustrator". CAD is meant for precision ...

However - there are many ways to skin a cat. Bottom line, the more QCAD tools you know the more easier becomes your job ...

[mathcubes]

Thanks. I actually thought it might have been impossible.

Your answer is very good and so thanks for taking out your time.

Math

[mathcubes]

mathcubes,

Hi and welcome to the forum.
QCAD is vector based and that would be as precise as possible and scaled just the same.
On how precise that is and on how certain a number in 64 bit floating point really is we can write a book or two.
For instance, the value 0.1000... can't be expressed exactly in floating point but it will be very very close to 0.1 in binary.
But that will never induce an error in the region of 0.19% like your Adobe Illustrator example.


I have to admit I needed to read your topic more than twice to get a glimpse of what you're at.
There is nothing as collision detection implemented in QCAD.
To start with, nothing in line-art or even hatched 'solid' is considered as a solid.
For that you need a high-end (expensive) parametric application that works with solid shapes.

For the circle problem I think it is easy.
A circle with a certain radius touching two other circles can be drawn with Draw .. Circle .. Two Tangents and Radius (CTR).
And for two circles that are 2 units apart the distance between the centers is 2R+2 or R1+R2+2 with unequal radii.
Or meaning that center 2 would lie on a circle with radius R1+2 around center 1 and vice versa.
The intersection of 2 construction circles will give you none, one or two exact solutions.
The same goes for touching what is zero units apart.

In your circle example there are some places where one should roll over another until it touches a third circle.
Rolling is keeping the center distance steady ... A construction circle radius = R1+R2.
Touching is again a certain center distance ... A second construction circle radius = R2+R3.
Where they intersect you can place circle 2 its center.

Or you could draw a CTR circle tangent to a circle and a construction circle that is 2 units wider than the other intended.

That should be perfect when measured up although it may display incorrect at extreme high zoom.
The reason here is that curved lines are displayed interpolated ... segmented.
At a certain zoom state touching curved shapes seems to drift apart, but they still touch mathematical.

For the squares it is less simple.
Just because they have corners sticking out.
Again this requires construction lines and QCAD has several tool for that.
But here we talk about sliding a corner along a face (= line) until another corner meets another face.
I would solve this by a parallel of the face trough the other corner with Draw .. Line .. Parallel (trough Point) (LG).
Then it is a question of moving the shape from one reference to another with Modify .. Move/Copy (MV)
Select the square to move, type MV, not copy or delete original, from point A to point B.


mathcubesProblem.png


And of course, every problem will have several unique solutions and several ways to solve them.
Rotating a square around a corner so another corner meets a face requires a construction circle around the corner trough the second corner.
Then you can rotate the shape around the corner so the the other corner is where the circle meets the face.
Hint: In that case you define the angles with the mouse cursor (not by value), that is the pointer button beside the angle field in the dialog.

Rather curious in what math is done on the cubes (... mathcubes)

Regards,
CVH

Thanks.... It was just the name I came up with for my own self when I was 9 or so. I just like it and so it sticks. I was obsessed with math and cubes were and still are my polyhedron... So I just put them together. With hindsight math isn't the best idea because I got now kids asking me to help them with their math homework or correct me with the 'spelling' because for them it's should have a 's' at the end.... I just say work smarter not harder, just use a calc or program something which helps you.

[CVH]

Thanks. I actually thought it might have been impossible.

Many things seems to be impossible until solved.

BTW: You can quote an individual line or part of text with selecting it before hitting the quote button ...
... But not while re-editing your post.

Regards,
CVH