Ok, Illustrator is also inaccurate :)

[eobet]

Since we're forced to learn Illustrator at the design school I'm currently attending, I took the chance to try some of the things I've been nagging about on Xara X.

Attached here is a very simple, succesful anti-aliasing error. Note how the red of the underlying objects filter through on the above, snapped to fit objects. (Since I come from a computer science college background, this is still rather suprising to me, since the absolutely first graphics coding assignment we had was to make a perfect circle from 360 triangles, and anti-alias them without any error at all... but I guess Xara and Illustrator's speed optimizations sacrifice some acurracy here... I just wish they wouldn't do it when I export to bitmaps.)

The second Xara X annoyance I have, that when I subtract two curved lines (ellipses mostly) Xara X vectorizes them AND sometimes leaves residue objects. I haven't managed to reproduce this in Illustrator yet, though.

[eobet]

Since we're forced to learn Illustrator at the design school I'm currently attending, I took the chance to try some of the things I've been nagging about on Xara X.

Attached here is a very simple, succesful anti-aliasing error. Note how the red of the underlying objects filter through on the above, snapped to fit objects. (Since I come from a computer science college background, this is still rather suprising to me, since the absolutely first graphics coding assignment we had was to make a perfect circle from 360 triangles, and anti-alias them without any error at all... but I guess Xara and Illustrator's speed optimizations sacrifice some acurracy here... I just wish they wouldn't do it when I export to bitmaps.)

The second Xara X annoyance I have, that when I subtract two curved lines (ellipses mostly) Xara X vectorizes them AND sometimes leaves residue objects. I haven't managed to reproduce this in Illustrator yet, though.

[gwpriester]

Can you post a larger image?

I am not able to see what you are describing at this size.

Gary

[eobet]

Sure.

Note the red border on the left of the grey shapes. Also note the ever so slight red tint between the two grey shapes.

In the below picture here there shouldn't be any red at all, since the red object is 100% completely hidden by the grey triangles placed on top of it (snapping should have made sure of that, but the anti-aliasing or occlusion algorithms cheats, and thus bleeds through color).

[Egg Bramhill]

Eobet
I can duplicate this effect easily. See attachment.4 shapes, all but the No 2 showing this effect. (No2 has no underlaying of shapes)
3 & 4 are just clones of te underlaying shape with the colour changed. In 3 you can see a red fringe around the circle. In 4 the top r.h text is Text with a clone, but it makes it appear bolder (something a lot of folks use to create better looking web button text)
No1 is a similar shape to yours, with a red underlay, and as you say, it has a red fringe. No 2 is a similar shape but by using Clone / Arrange shapes / Slice, the offending underlay is removed and the fringe is eliminated (unless you argue that there now appears to be a white fringe between the red & grey areas)

Not sure if this is Xara's Antialiasing or a screen resolution / graphics card issue tho or niether. After all A/A is only a means of dithering to compensate for a pixel based display not being able to render a true straight line, a method of removing jaggies.

I don't see it as a real problem tho. If it shows up to clearly I always go along with No2, the Clone / Arrange / Slice method or select the underlaying shape and resize it very slightly to less than the one above.

Egg

[MEB]

I´m having some trouble with those issues too.
When working in some complex illustrations i usually intersect /add /subtract shapes in order to get a final shape that reflects "the form" that will be seen on screen (instead of overlaying shapes until they cover the (surrounded) parts that will not be seen in the final illustration) - this way i can identify all the shapes quickly by their "shape/form" - hope this makes sense.
The problem with this appraoch is that those issues described by eobet will appear in several areas of the illustration speccialy when there´s a high contrast between the shape´s colors.
Correcting all those problematic areas as Egg sugested consumes too much time and is boring as h...
I hope Xara can fix those issues. There´s nothing worst than spending some serious money to get a decent print of our work just to discover
that one of those problems become too much visible and requires correction http://www.talkgraphics.com/images/smilies/frown.gif ... and a new print.

Miguel B.

[Egg Bramhill]

The problem is being created by antialiasing. A/A allows us to view a shape with smooth lines. This seems to be done by giving pixels at the outer limits varying degrees of transparency of that colour. When you export 2 overlaying objects, these areas of transparency overlay as well, giving you a combination of the 2 transparencies.
It's something we're just going to have to live with I'm afraid, until someone creates terabyte pixel screens and tera pixel printing, making A/A redundant.
Egg

[Egg Bramhill]

The only way to remove this is to set the view to normal. This removes the fringinging, but reintroduces jaggies. The attachment is of the 2 circles at normal viewing. No fringe but jagged.

[eobet]

Egg, I'm sorry, but your example 2 still has a color which bleeds through, namely the white of the background (and if you export to a PNG with alpha, you might get transparent pixels between the polygons, if you are very unlucky).

The only way to get rid of this is to remove the anti-aliasing completely and export at 4X or 8X the size by yourself, but then you loose some of the ease of working with a 100% scaled picture.

[RTK]

I'm sure it's covered in this thread - but I can't decipher it...

But in case some are are confused as I am - here is a quick example of how to avoid ALL "jaggies" ALL the time. Yes, it might be some extra work if you are layering thousands of objects - but hey, Xara X is a vector application after all. If you are suffering incredibly from these issues because you are layering that many objects, perhaps you should use a bitmap application instead?

AND this is not a Xara X issue as eobet pointed out - it's a vector application problem. They all have them. At one point I was excited about Freehand... but heck, it was a nightmare when it came to AA.