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El Gringotte

enter X,Y coordinates for rotation center

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Guys,

 

since it's somewhat tricky to accurately locate the rotation center, it would be nice if the user could enter its X,Y coordinates, same as autocad / catia / solidworks...

 

Cheers!

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Place 2 guides that cross at the co-ordinates you want. W. snapping on, the rotational center , v. 1.5.6, will snap there. Not too much work.


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What software and to rotate what?

 

In Affinity Photo, if you place an object (like a shape) and go to the "Transform" panel the X Y coordinates are for the selected point. i.e. If you click on the centre control point (the 9 little points in a square) you get the X Y coordinates of that point. Click on the top left control point and you get the X Y coordinates for that point. You can then position whichever point you have just selected precisely. It will also rotate around the point you have selected.

 

Or am I missing something?


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thanks guys. one can enter X Y Z coordinates of the rotation center in all CAD software I know ... Think it would be very handy for AD.

Thanks Gdenby, that's the method I'm using. A bit long compare to what I was used to ;)

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In Affinity Photo, if you place an object (like a shape) and go to the "Transform" panel the X Y coordinates are for the selected point. i.e. If you click on the centre control point (the 9 little points in a square) you get the X Y coordinates of that point. Click on the top left control point and you get the X Y coordinates for that point. You can then position whichever point you have just selected precisely. It will also rotate around the point you have selected.

The 1.6 beta versions now let you use the rotation center set in the workspace instead of the anchor points in the Transform panel for this, but there is still no way to set the rotation center numerically.


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The 1.6 beta versions now let you use the rotation center set in the workspace instead of the anchor points in the Transform panel for this, but there is still no way to set the rotation center numerically.

Every search of the rotation point in a construction, a really simple example is the exposure X-logo, is very tedious if the rotation center point can not be entered numerically. The coordinates would be known, since they correspond to the center of the logo.

I really can not understand that such an important and useful possibility is not realized.

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Every search of the rotation point in a construction, a really simple example is the exposure X-logo, is very tedious if the rotation center point can not be entered numerically. The coordinates would be known, since they correspond to the center of the logo.

I really can not understand that such an important and useful possibility is not realized.

 

I'm unfamiliar with exposure X - logo. But I think a counter argument could be made that needing to do numeric entry is tedious.  


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I'm unfamiliar with exposure X - logo. But I think a counter argument could be made that needing to do numeric entry is tedious.  

Exposure is a software of AlienSkin. https://www.alienskin.com/. The link because I have no rights to the direct presentation.

The logo is easy on the one hand, on the other hand a nice exercise for AD. The centre point of the outer ring is, of course, the centre of rotation of all other parts. Using the method of help lines and intersections, you can quickly make a small mistake despite the tools of AD, then the copying around the inaccurate centre and you can make everything new. It is a construction, and for a construction an exact, thus numerical, input is meaningful.

There are so many input fields when transforming, the strokes, etc., a numeric input of a rotation centre, which is identical to the centre of a circle, should be self-evident.

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Every search of the rotation point in a construction, a really simple example is the exposure X-logo, is very tedious if the rotation center point can not be entered numerically. The coordinates would be known, since they correspond to the center of the logo.

That depends on what you consider to be the center. The coordinates for certain simple geometries with some degree of symmetry are easy to determine, but consider for example a teardrop shape or an irregular polygon. For such shapes the "center" could mean any of several different things -- it could refer to the center of the bounding box around the shape or something else, for example one or more of the several geometric centers listed here.

 

Even for something as simple as a bilaterally symmetric tear drop shape, the only coordinate that is straightforward to determine is the one along its axis of symmetry, but the other coordinate could be at many different points along that axis, depending on the kind of geometric center most suitable for whatever kind of rotational transform you want to perform.


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There are many drawings in which the rotation point is easily chosen with snapping, There are many drawings in which the rotation point can be easily selected or the exact coordinates are unimportant. However, constructing of geometric components it were very helpful to enter the rotation point with x / y coordinates. An input of geometrically relevant points, such as the centre point of a circle by a corresponding selection of the object, would be a great alternative.

This is my opinion, I find it a pity that AD does not offer. The Exposure X logo is a simple but powerful example.

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An input of geometrically relevant points, such as the centre point of a circle by a corresponding selection of the object, would be a great alternative.

This is my opinion, I find it a pity that AD does not offer. The Exposure X logo is a simple but powerful example.

I don't understand something -- does the rotation center not snap to the center of a circle, ellipse, or similarly symmetric shape for you when you drag it in the workspace? This seems to me to be a lot faster & potentially more accurate than entering two field values.


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I don't understand something -- does the rotation center not snap to the center of a circle, ellipse, or similarly symmetric shape for you when you drag it in the workspace? This seems to me to be a lot faster & potentially more accurate than entering two field values.

Yes it does, but snapping works with a certain tolerance, which can not be needed within an exact construction. With the available tools you get a result, but it is unnecessarily difficult and error-prone. An additional option by entering x/y coordinates would be extremely helpful and useful.

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Yes it does, but snapping works with a certain tolerance, which can not be needed within an exact construction. With the available tools you get a result, but it is unnecessarily difficult and error-prone. An additional option by entering x/y coordinates would be extremely helpful and useful.

I am sorry but I do not understand what you mean by this. The snapping tolerance is the same as the internal precision of the app, which I believe one of the developers said was the equivalent of about 20 decimal places. Even if you could set the x/y coordinates of the center of rotation in numeric field values, it seems to me that you can't possibly do better than that. Entering numeric values would be much more prone to errors than using bounding box centers, or where necessary & possible geometric constructions to determine whichever of the many geometric centers you want to use.

 

Can you explain which geometric center(s) you are considering & maybe give an example of when calculating its x/y coordinates by hand & entering them in field values would be more accurate/less error prone than by using the available tools?

 

Thanks.


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Yes, I'd be interested to know what you mean also....?

 

Snapping is performed to be as numerically accurate as is possible depending on what is being snapped. Straight line intersections will be numerically accurate. The only area where precision will be an issue is where snapping is made to mid-curves or intersections between two curves, where the calculations can only be made by using subdivision of the curve to within a predetermined tolerance.

 

That said, the calculations of straight line intersections through curves is done numerically, so will be accurate to somewhere near double precision, as will the calculation of curve bounds.  This means that for those cases, the precision for snapping is likely to be greater than our rendering accuracy of curves when zoomed in (well over 1,000,000%).

 

Snapping to points (such as the key-point centre of an ellipse) is going to be more than accurate enough.


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The example with the Exposure X logo shows quite well that a numerical input of the rotation point or the assumption of the centre of a circle as a rotation point would be very useful. The usefulness is, of course, only achieved with constructions, especially if  shapes have to be precisely fitted within circles. There are various machined parts, which in this example are each rotated by 60°. Also the centre is neither a circle nor a rectangle, the 6 side lines are small arcs. If one has the idea for this logo, the realization happens only by constructing the 6 coloured segments and the middle part. I was perhaps too clumsy, and the multiplication and rotation with ^J was difficult because if the point of rotation was not exactly the centre of the circle and of course the deviation grew with every copy.

After a few attempts I made it, but I missed a numerical input of the rotation point. This does not have to be calculated, because e.g. when transforming, many points are displayed as x/y coordinates, so also candidates for a rotation point. And copy & paste are indeed common methods when dealing with programs.
I thought I would not know where such an input can be made, because there are various inputs, for stroke, transforming, etc., I need not enumerate them.
However, I have to realize that Serif does not have this option, although this would be very simple, space is sufficient in the line with the icon of the rotation point.
But I have resigned myself anyway, but I find it a shame.

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I think you need to be aware that this is not CAD software.  It's primary use is for artistic drawing.  We are not doing precise calculations with geometric primitives - everything is approximated to cubic beziers.  Once a shapes has been created, it is in cubic form, and all further processing on it will be on that data, not the notion of the original primitive - and that includes circles/ellipses.


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Also, as far as positioning the rotation centre, the rotation point can be snapped just as anything else.  So, I can't se why you cannot snap the rotation centre to the centre of the circles bounds or key point...?


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I was perhaps too clumsy, and the multiplication and rotation with ^J was difficult because if the point of rotation was not exactly the centre of the circle and of course the deviation grew with every copy.

I think Ben may have already made this clear in his last post, but you may not have noticed that when the rotation center is displayed & you drag it with the Move tool, a tiny dot is displayed at the default center point. It is a snapping point, so if for some reason you have moved it off-center, you can snap it back to that point.

 

I think that for circles, ellipses, rectangles, radially symmetric predefined shapes (like stars), & perhaps a few other shapes, this point is the same as the shape's centroid. (I am not sure about this, so maybe Ben can say more about that.) Anyway, for some other shapes like triangles & many irregular polygons, the centroid can be determined by simple geometric constructions, like the intersection of diagonals or of vertices & mid-points, which can be drawn in AD with snapping to key points enabled. The rotation center will also snap to those intersections, so this should work for those shapes (if the centroid is the center you want to use).

 

For other kinds of centers & for shapes that do not lend themselves to simple geometric constructions, I have no idea how to set them precisely (to the limits of the app), but I do not see how being able to enter numeric x/y coordinates would make this any easier.


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I think the original request had more to do with arbitrary rotation centers.... One that we can now place manually.

So I see where El Gringotte is coming from. It would be nice to have input fields (or at least an info panel to show where the cursor is when dragging the center around). Right now we have to visually guess or use one of the workarounds outlined above by gdenby and toltec.

 

But the manually placed rotation center coordinates ARE showing up in the numeric fields, just in a weird way.

 

If u turn on Show Rotation Center and move it, the Navigator fields don't reflect that spot. But, if u then actually start to do a rotation, the correct numbers appear. 

post-12544-0-27794500-1497044727_thumb.jpg

If the center has been moved and u turn off Show Rotation Center those coordinates NOW show up in the x,y fields but, of course, that is not the current rotation center.

post-12544-0-00157600-1497044741_thumb.jpg

If u turn on and move the rotation center and hit reset bounding box the new coordinates will stick in the x,y fields. 

I think there's more behavior to describe, but you get the idea.

 

The point is that the numeric panel does appear to know where the center is..... at times. We just can't interact with them. Once touched in the transform panel they revert to a translate operation instead of rotation. In the absence of dedicated fields, maybe a toggle between translate and rotate?

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JimmyJack, 

 

I think I understand what you have demonstrated, but I am still trying to figure out what practical value there would be for being able to set the rotation center's x/y coordinates numerically.

 

The rotation center is a property of the object itself rather than some arbitrary point in the workspace -- if you move the object, the rotation center moves with it -- so this would not be useful for setting absolute workspace x/y coordinates for its position. For setting the coordinates relative to the object or to other objects, snapping does the job, albeit sometimes at the cost of constructing intersecting lines or the like. Where that isn't possible, I don't see how setting the coordinates numerically would be any better -- how would those values be calculated?

 

Can you think of a usage scenario where it would?


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JimmyJack, 

 

The rotation center is a property of the object itself rather than some arbitrary point in the workspace  -- ..............-- how would those values be calculated?

 

Of course, the rotation centre point belongs to the object that is to be rotated. But the centre of rotation is not to be considered isolated, it is also part of the whole drawing. And the centre of rotation of an object can also be that of another object. It does not serve the flow of the work, if one can not repeat a chosen choice with another object, because one must find a point again. As with many other editing, there are different ways of personal preferences and different ways. I do not want to evaluate them.

I am familiar with technical drawings, and it is not so that the rotation point has to be calculated. AD knows it naturally, otherwise the algorithm could not rotate objects. It would only be that the coordinates are displayed, and if they are displayed, you could click them and change the values ​​via the keyboard.

AD is basically a technical drawing program that presents itself so that it does not scare graphic artists. Just like all of the vector drawing programs too.

But as already mentioned, I have resigned myself to the fact that currently a numerical input of the rotation centre point is not possible. Let's see what future versions will bring.

 

... just in a weird way.

This is a more than strange way, but this does not solve the problem of non-existing input fields. If I want to rotate a second object around the centre of an existing circle, then the coordinates of the centre point of the circle are known, can be viewed and modified in "TRANSFORM". The actual coordinates of the rotation point are known in AD, but they are not displayed. Ätsch, I can only say. But the Google Translator can not translate the children's language, they say that if they stick someone's tongue out to say, I know it, but I do not tell you.

 

Thanks for your help and patience.

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SunRiseMoon, I was asking how a user would calculate the x/y coordinates for the centre of rotation -- if you can't do that as accurately or repeatably as by using snapping, what is the point of numerical input of those values? (Remember what Ben said earlier about the numerical precision of snapping.)

 

When the desired rotation center is some other object, just snap it to that, or to a construction like a pair of intersecting straight lines or whatever else is convenient. When the design is complete you can hide or delete the reference construction.


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JimmyJack, 

 

I think I understand what you have demonstrated, but I am still trying to figure out what practical value there would be for being able to set the rotation center's x/y coordinates numerically.

 

The rotation center is a property of the object itself rather than some arbitrary point in the workspace -- if you move the object, the rotation center moves with it -- so this would not be useful for setting absolute workspace x/y coordinates for its position. For setting the coordinates relative to the object or to other objects, snapping does the job, albeit sometimes at the cost of constructing intersecting lines or the like. Where that isn't possible, I don't see how setting the coordinates numerically would be any better -- how would those values be calculated?

 

Can you think of a usage scenario where it would?

 

Yes, as Ben points out this is not CAD software but sometimes a little more precision is needed. Just as now we cannot fully trust CMD J rotations when using the on canvas rotation handle (even though there's real time on screen numeric feedback). We have to use the input field in the transform panel to be precise. 

 

But you're right. Most of the time a quick drag and drop of the rotation center to an arbitrary-ish spot may be just fine. And yes, wherever you go there you are.... the rotation is relative to the object. But coordinates are still just coordinates. And they ARE showing up in the numeric input fields. Even if you just need things to be tighter than usual I think it's a whole lot easier to have the option to type/tweak two numbers in the transform panel rather then calling up the guides manager, typing specific numbers there (in two places) and then having to drag and snap to that intersection. Or having to draw two extra interesting objects and then dragging the center point to snap and then have to delete said objects. Or drawing one extra object and have to type in specific coordinates for one of those corners (or move it carefully) in order to then use snapping for the original object. All those work.... it's just a lot of work.

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All those work.... it's just a lot of work.

Hmmm. I just did a quick experiment. To set my "reference" rotation center I used the Pen tool in line mode to create a short pair of intersecting lines, one vertical & the other horizontal. They can be placed precisely (to the limits of the app) anywhere on (or even off) the canvas using the numeric fields in the Transform panel. Stroke size & line length don't matter, just where they intersect, so this took about 4 seconds.

 

I then added some other objects, some duplicates some not, clicked the Show Rotation Center button & started dragging their centers to my reference. All snapped to the intersection of the two lines quickly & easily. Rotations about that reference center point work fine. For the final output I could delete the two lines but since I might want to edit the AD file later, I just hide them.

 

So I do not think this is a lot of work. In fact, I think it is a whole lot less work than trying to enter the center coordinates numerically (possibly for each of several different objects!), & making sure the values have been entered correctly & with sufficient decimal precision to be placed exactly where desired.


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In 1.6 the Transform panel has been changed so it reflects the rotation centre when it is visible. This gives you its exact x,y coordinates. You can enter new values, and that will move the rotation centre, but it will also move the entire object. So I don't think this is quite what you want, but it should help.

 

(The current Mac beta has a bug whereby the Transform panel does not update if you drag the rotation centre with the mouse, but we'll get that fixed.)

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