INTERSECT is NOT accurate...by between 0.011" & 0.014"

I handle the creation of production files for a sign company. We recently began work on a very large scale monument with a 44' radius top. I used INTERSECT to create the panels to be routed for that portion only to constantly come up with an incorrect size (top to bottom) on the radius of each panel. On closer inspection I realized that whenever I used INTERSECT to create the panel for some reason it creates a flawed section off by .013" all the way across the shape. My understanding has always been that INTERSECT is supposed to create an exact section from the two overlapping shapes selected but that is now apparently not the case. This seems to only be the case with very large scale vectors in 1:1. It works perfectly with small scale shapes and creates a section exactly the size of the overlapped sections...but the larger the shape the greater the size discrepancy. Has anyone else encountered this issue and/or know a fix for it?

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Eskimo over 7 years ago

You might have posted in the Corel Connect forum by accident. I would recommend posting in the CorelDraw X7 forum instead; you will get more and better eyeballs seeing your post.

I can confirm that when I try what you describe in CorelDraw, I see similar inaccuracies.

I don't know if it's a bug, or if it is fundamentally tied to how CorelDraw mathematically describes the geometry, and the level of precision with which the values for that are stored and manipulated.
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vectormage over 7 years ago in reply to Eskimo

Thanks for the heads up. Didn't realize the post wasn't in the best location.

As for your opinion on the issue... "fundamentally tied to how CorelDraw mathematically describes the geometry" -
In the case of shapes on 10" or 15" there doesn't SEEM to be an inaccuracy-though after sleeping on this I came to realize there most likely IS one, just so minuscule that it's undetectable. However working 1:1 at sizes exceeding 20'-50' that same inaccuracy became quite evident. I have a hypothesis on this - to basically work with intersect only at reduced scale then increase the shape to 1:1 and note the resulting accuracy.

The fact of whether its a bug or not shouldn't be the question...it is an inaccuracy in the functionality of the software that can have detrimental effects in my work - cnc waterjet, laser and plotter production...so it warrants being addressed.
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Eskimo over 7 years ago in reply to vectormage

Please understand that I was not dismissing your concern. As a long-time user of CorelDraw, I think that I have become a bit jaded when it comes to hoping that bugs will get (1) noticed by Corel, (2) taken seriously by them, and (3) fixed by them.

I would suggest that you try to find a way to officially report this issue to them. If you get an answer about this, then it would be great for you to post that information back to this thread. I'm interested in the answer, and questions/answers in these forums are a great resource for others in the future.

Although this is not exactly the same thing, you might find some of the observations in this thread interesting. Smaller objects with small inaccuracies - but inaccuracies nonetheless.
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vectormage over 7 years ago in reply to Eskimo

[In the case of shapes of 10" or 15" there doesn't SEEM to be an inaccuracy-though after sleeping on this I came to realize there most likely IS one, just so minuscule that it's undetectable.]

My theory was correct. I also have Corel x5 on the same PC. I used x5 instead to see if the same issue would occur verifying it to be a bug in the software. It did indeed. Next I tested my hypothesis quoted above - still using x5. I was correct again. The discrepancy occurs no matter the size of the intersected objects, however overall object size VS scale DOEs determine how extreme the discrepancy will be. My original figure was .011-.014". When I scaled it down to ¼"=1' - intersected it at that size - then pasted it into the same drawing with the .013 difference - increased it to 1:1 ... there was a discrepancy, but it was not large enough to make a fundamental difference...something like .00000032. Conclusion - working in the Corel software environment, the use of INTERSECT should be limited to scaled DOWN vectors (NOT FULL SIZED or LARGER THAN FULL SIZE). Use of INTERSECT in any other way will likely produce fundamental inaccuracies - especially in the case of CNC Machining, Laser cutting and\or Plotting. Until Corel announces a fix, the above suggestion on the use of INTERSECT should be followed.
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Myron over 7 years ago in reply to vectormage

Can you describe the process you are using in short form. i.e. draw a shape at size A and another shape at size B then use one to intersect the other....yada yada yada
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vectormage over 7 years ago in reply to Myron

Sure...as it states in my first post, the radius is 44' across 2 horizontal 5' x 10' alum sheets. So in a new drawing scaled 1:1 create an 88' circle, two 5' x 10' rectangles horizontal for a total of 20' wide. Group or Combine them (DO NOT WELD THEM) and overlap the circle with the "north" node on mid-center of the two rectangles(as in with the "north" node selected move down the center line between the rectangles til it says midpoint and stop) . Select the rectangles first then the circle(with no fill I don't think it matters) and intersect. You should immediately notice the top line change. When you zoom in on it you'll see the point of my post.
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Myron over 7 years ago in reply to vectormage

I see the dilemma. Interesting too that even using the smart fill is a tad more accurate but still not "dead on" as one would expect.
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