Autocad solid hatch PDF translation problem in CC 2015 (autocad content only works with antialiasing off)

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I have Photoshop CS5 which translates AutoCad generated drawings with solid hatch perfectly into smooth colour fields. I recently got CC2015 and it does a terrible job, with the solid hatch lines (the way Autocad renders the hatch is a series of closely spaced lines which create a solid fill) all out of alignment and white spaces in between. Testing with Acrobat preferences shows that it relates to the variable preference-page display- "Smooth Line Art" - by toggling this on in Acrobat you can see two results of the the CS5 version (smooth line art off) and the horrible scratchy CC 2015 version (smooth line art on). This is my principle use of the software, and I work at very high resolutions, so I am pretty annoyed at this step backwards in my expensive new software. Due to this problem I have to keep my CS5 going, just to translate PDF's into acceptable raster images. Is there any setting in CC where this can be a translation variable, or at worst in a plug-in, and can it be added please Adobe? I can't be the only person wanting to translate hatched Autocad drawings into image file formats and hatch the solid areas look solid rather than something that has been shredded and scratched. It appears the "smooth line art" setting is default in the translation, and it really should not be.
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RH

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Posted 2 years ago

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Chris Cox

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That is a problem in the way the file was created. It looks like it would only rasterize correctly with antialiasing disabled. (and even with CS5's lower quality rasterization you got some artifacts at edges)
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RH

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Hi Chris, thanks for the speedy reply.

OK I tested it. Sorry my last sample was zoomed in very high 8000%, as it was where I was studying the problem trying to figure out what was going wrong.

I have made a new test file to show it at a good scale. I tried uploading the original pdf but not allowed, I could email it to you if you want to test yourself.

CS5 has far higher quality rasterising than CC 2015, samples attached.

CS5 with anti aliasing on, has nice smooth curves, the colours are even.

CC2015 with anti aliasing on, it gets the horrible scratchy lines

CC2015 with anti aliasing off, colour regions are smooth but the curves are pixelated uneven in thickness due to no antialiasing. This output is not acceptable to me as it is too jaggy for my artwork - it shows unfortunately in prints even at 600 dpi. So CC2015 can't give me what CS5 does, which is smooth curves, and smooth colour zones.

This means CS5 still has a superior translation algorithm, which is very annoying after upgrading..I can't do what I used to be able to do and am now paying monthly for something that can't give me a good output. Is there any way to be able to get the CS5 PDF translation algorithm back into CC 2015 as an option or setting?

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No, CS5 had much, much lower quality rendering -- we greatly improved the rendering quality since then. (basically CS5 barely had any antialiasing, and it was pretty clumsy).
But, artifacts may have been hidden by that low quality rendering show up more often, especially with abutting shapes. The problem is in the way the files are created (because abutting shapes will always show artifacts unless antialiasing is turned off).
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Chris Cox

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There is a request to offer the older, poorer antialiasing for special cases (like some InDesign files that show artifacts at resolutions lower than the original) - but I can't find it right now.
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RH

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Hi Chris

What is the criteria for saying the new one is better and improved rendering? I realise that photoshop is doing some 3d and more complex things, other things which perhaps this "improved" rendering quality might be good for, but it is not clear to me now what this might be - or is it for typography?

But for line art graphics, which is essentially "abutting shapes" of different colours and tones, then surely stating that in this case the new antialiasing will be "always showing artefacts" is a huge problem. I am not sure what was "clumsy" about it before, to me it did it seamlessly and well.

I guess in some digital engineering purist universe there might be a different explanation of what is "better and improved" but if something gives me worse visual output, and if the software used to do something well and now does it badly, I can't really understand how this is considered better by Adobe.

Since "older, poorer" anti aliasing, gives much better visual output, and the "improved" is guaranteed by give artefacts, at least give us the option of choosing something can give an equal output to past versions, given the same input. I don't think any new version of a software should lose functionality, or be unable to handle a type of input that it used to be able to handle very well.

If not, then supply a PDF printer driver plug in for Autocad to give the output in the new compliant format that CC needs so that the softwares can work together.
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Chris Cox

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The new antialiasing produces more distinct levels of values on edges (fewer jaggies), and was evaluated with a very large body of test files.

However, we did not test with obviously broken files such as you are using -- abutting shapes simply will not render as solid when antialiasing is used, and they even sometimes break when antialiasing is off. (and you still have some artifacts in your old CS5 examples)

No, most vector art does not have abutting shapes, but overlaid shapes, and has no such problem. In this case, someone at AutoCad made some bad assumptions about rasterization of their PDF files and failed to do much testing of their generated files. You didn't lose functionality, but improved quality of the rendering made the artifacts already existing in your PDF files more obvious.

This is, unfortunately, something that only AutoCad can really solve by changing the way they create PDF files.

We might be able to offer some choices in Photoshop - but the artifacts will still show up in some places and some resolutions, because the PDF files are generated in a way that cannot always be rasterized without artifacts.
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RH

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Thanks Chris

Did Adobe test CAD output files from the architectural industry, which are only abutting areas rather than overlapping due to the very high accuracy of the software?

Anyone using vector CAD will be generating abutting areas as the whole point of the software is extreme accuracy and avoiding elements sharing the same 2D or 3D space (e.g. all the clash detection software being incorporated into BIM now to ensure absolutely no overlaps between elements)

It is common to generate image output in CAD from working models and then develop them into presentation images in Photoshop, so this is something that affects a large industry and customer base for you.

The edge artefacts are because Autocad upon printing makes a series of very small straight lines to render curves, and these do not always line up between neighbouring elements, but the internal area scratches are because Photoshop is detecting the parallel lines that make up the toning within the triangulated regions and is trying to do something clever with them that is not needed...expressing them as separated lines and not toned areas.

CS5 did the edges and curves nicely and did not mess up the areas of toning, so it was perfect for the CAD industry.

I can address the edge misalignments via the plot scale and paper size to force smaller triangulation but I can't fix the toning issue in CAD as this is the Photoshop algorithm in the way it treats the solid hatch.

So if you can solve the parallel line hatch expression in the anti aliasing , that is all I need, the scratchy uneven tones are very difficult to do anything with to fix them without losing crispness or information in the image.

Richard
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Chris Cox

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I'm not sure exactly what AutoCad generated files were tested, and I can't easily browse our thousands of test files while I'm traveling.
Again, most vector files wouldn't be a problem - but it looks like Autocad is subdividing solid color areas into a lot of smaller shapes, and that just isn't going to rasterize correctly with antialiasing (and may still have problems without antialiasing). Photoshop is just rasterizing the shapes created by AutoCad, not detecting or changing anything. They are separate lines because that is how AutoCad wrote them into the PDF file (which is a really, really bad idea). This is not a "Photoshop algorithm", this is simply a failing of AutoCad's PDF generation when you use antialiasing to rasterize the file. This has to be fixed in the AutoCad software. We might provide a sorta-workaround in Photoshop, but we can't avoid artifacts in a file written that badly.
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RH

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HI Chris

You should take a break if travelling for the holidays! I'll follow up in the New Year, but hope you can help find a solution.

Merry Christmas,

Richard