Alignment Tool-Question

[PaulB]

Hi Folks..
I'm doing something wrong..
If I were to draw a circle and a triangle, two seperate objects, I should be able to align the triangle inside the circle... aligned to the centre points. However, Xara X doesn't seem to quite do that. The two will clearly be off-centre.
I am clearly doing something wrong, or I don't understand the principal of alignment.
Can someone help me, please?

[PaulB]

Hi Folks..
I'm doing something wrong..
If I were to draw a circle and a triangle, two seperate objects, I should be able to align the triangle inside the circle... aligned to the centre points. However, Xara X doesn't seem to quite do that. The two will clearly be off-centre.
I am clearly doing something wrong, or I don't understand the principal of alignment.
Can someone help me, please?

[masque]

Paul
Thats a suprisingly good question.
I had assumed that a perfect circle, drawn while holding ctrl and a similarly drawn triangle would align to the centre points, but they clearly don't. Symetrical star shapes, perfect squares align as you would expect so why do triangles get offset as they do?
I don't particularly want to do it, but I would like to know the answer as to why I can't in case I should want to soon.

derek

[Soquili]

Hi Paul,

You aren't doing anything wrong. I've found that any shape with an odd number of vertexes will not properly align inside a circle. A work around is to temporarily change the triangle (or other shape) to one with an even number of vertexes, say a square. Align then convert the shape back to the shape you want.

[mckinney]

It looks to me like Xara is simply using a different definition of "center" for the alignment tool than it is for the quickshape tool.

The "x" in the middle of each quickshape appears to be the centroid or similar. See http://faculty.evansville.edu/ck6/tcenters/index.html for a list of different definitions of triangle centers, for example.

The "center" as defined by the alignment tool appears to make use of the extents of the shapes in the X and Y directions.

If you take a look at Soquili's first example above, you will see that the alignment tool has positioned the triangle so that the distance between the upper horizontal edge of the triangle and the top of the circle is the same as the distance between the lower point of the triangle and the bottom of the circle. In Soquili's last example, although the centroids of the two shapes are lined up, there is clearly more space between the top of the triangle and the top of the circle than there is between the bottom of the triangle and the bottom of the circle.

As Soquili noted, you'll see the effect for any quickshape with an odd number of sides. You'll also notice it for more irregular shapes (non-quickshapes) but it may not be as obvious as Xara doesn't mark the centroid for non-quickshapes.

Another workaround for lining up the centroids of quickshapes is to make sure that "snap to objects" is turned on and drag one object's center near the other's.

- Pete

[PaulB]

Thanks a bunch, Pete and Soquili.

That seems to be where my mental fart was.... an odd number of sides was and is the path to my answer.

You're silution was the fastest, Soquili and the reason for that WAS in:
http://faculty.evansville.edu/ck6/tcenters/index.html

Thanks again

[amoore]

> http://faculty.evansville.edu/ck6/tcenters/index.html

That's amazing!
But how will I ever know which center to align on? http://www.talkgraphics.com/images/smilies/eek.gif

http://www.talkgraphics.com/images/smilies/wink.gif http://www.talkgraphics.com/images/smilies/wink.gif http://www.talkgraphics.com/images/smilies/wink.gif

[jclements]

As stated in other threads, there certainly seems to be room for improvement for the alignment functions in Xara X1. I hope they are near the top "to-do" list.

A lot of time can be spent using work-arounds to solve alignment issues.