angle fields

[Ed Nadie]

To interpret the values in the angle fields ('A') on the shape editor's infobar, it is necessary to know how XX measures the angle, and which line the value refers to.

With the node as the center of an imaginary clock, always measure from zero at the three o'clock position. Counter clockwise measures positive degrees; clockwise gives negative values.

The 'A' values depend on the direction of the line. There are two 'A' fields on the shape editor's infobar -- the left hand one gives the angle of the line closer to the line's beginning (the tail), the right hand field the angle of the line closer to the line's end (the arrowhead).

If you don't know the direction of a line, you can easily judge which line a value refers to by remembering that the angle is measured beginning at a three o'clock zero point, with positive values being counter clockwise. Also, when the two lines are obviously different lengths, the different values in the Length fields ('L') will reveal which line an angle value refers to.

The attachment illustrates the values in the left and right 'A' fields. If the direction of the lines was reversed, the values in the left and right fields would simply switch. The tail symbol marks the beginning of the line, and the green dots mark three o'clock zero points.

Ed Nadie

[Ed Nadie]

To interpret the values in the angle fields ('A') on the shape editor's infobar, it is necessary to know how XX measures the angle, and which line the value refers to.

With the node as the center of an imaginary clock, always measure from zero at the three o'clock position. Counter clockwise measures positive degrees; clockwise gives negative values.

The 'A' values depend on the direction of the line. There are two 'A' fields on the shape editor's infobar -- the left hand one gives the angle of the line closer to the line's beginning (the tail), the right hand field the angle of the line closer to the line's end (the arrowhead).

If you don't know the direction of a line, you can easily judge which line a value refers to by remembering that the angle is measured beginning at a three o'clock zero point, with positive values being counter clockwise. Also, when the two lines are obviously different lengths, the different values in the Length fields ('L') will reveal which line an angle value refers to.

The attachment illustrates the values in the left and right 'A' fields. If the direction of the lines was reversed, the values in the left and right fields would simply switch. The tail symbol marks the beginning of the line, and the green dots mark three o'clock zero points.

Ed Nadie

[tonylondon]

I like your visual explanation Ed, so much easier than just a textual one and one that is easy to retain. It might be worth just adding that to straighten up lines to horizontal or vertical it is only necessary to convert the value to the nearest multiple of 90, Tony

[jclements]

Ed, glad to see Troutdale has a Xara user!

Ed and others, if you have not had a chance to browse earlier postings, there a some good little tid-bits on node editing ... its just a matter of finding them [img]/infopop/emoticons/icon_smile.gif[/img]

An earlier forum posting described how you can select multiple objects, then with the Shape Editor tool (F4), shift-select nodes from any of the selected objects and move all the selected nodes at one time by dragging them with the mouse.

In the Guest Tutorial area at www.xaraxone.com, there is an isometric tutorial. On bottom half of page 3, there is some more info on node (called "points" in Xara) editing and the Info Bar. Also, later in the tutorial, it mentions that the distance from one node to another (of a line segment) can be changed via the Info Bar without out changing a line segment's slope (angle).

Hope this helps.

[Ed Nadie]

In the paper and pencil world, the usual way to draw a line is to start at a point, and draw the line with its angle measured relative to its starting point. In XX-land, this isn't the case because a line's angle is defined relative to the opposite end. This is convenient for computer logic, because a line only has a slope to define with the second point. Unfortunately this situation will inevitably be confusing, because it doesn't correspond to the way people work.

The way most people probably end up drawing a line from a point at a specific angle is to set the angle from it's starting point, which will rotate the line out of position, then nudge the whole line into place, then adjust the length.

If you want to keep the starting point of a line in place while moving its end, and define the angle from the line's beginning, and be guided by the 'A' field values, you need to subtract the absolute value of your intended angle from 180 and reverse the sign. (Angles measured from opposite ends of a line will have opposite signs.)

Another way to do this: draw any line from your starting point, and enter your intended angle directly in the line's 'A' field -- but with the sign reversed. Then ctrl-drag and flop the line with the selector tool. This way you don't have to do any arithmetic, and the line will stay on its starting point when you flop it.

A real solution to this confusion would be if the 'A' fields displayed the angles of the adjacent line segments relative to the previous and next nodes, instead of the current definition. This would allow us to draw angles in a way that made more sense, and still be consistent for measuring the angles of preexisting lines.

-- Ed Nadie

[Ed Nadie]

John,

Your isometric tutorial is remarkable! I've downloaded it and intend to put it to good use within the next few weeks.

Cheers!
Ed Nadie

[Clements]

Ed, thank you. Have you ever used Xara for doing perspective work? Got any tips?