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Decals cause artifacts on objects set to not receive them under forward rendering with MSAA

alt text

This appears to be very reminiscent of reminiscent of this artifact, but the solution does not solve this issue. https://docs.unrealengine.com/latest/INT/Engine/Actors/DecalActor/#the2x2blockartifactsfix

Step 1) Switch to Forward rendering

Step 2) Change AA to MSAA

Step 3) Create a decal with a transparent and opaque area such as the one above. Ensure the bounds exceed the vertical height difference between the two objects.

Step 4) Create two brushes, raise the second one slightly and make it be partially covered by the decal as shown above, set receive decals to false.

Step 5) Set MSAA samples to 4 for most noticeable result.

Project displaying this. https://www.dropbox.com/s/cyzmn3hfk9rnt92/decalbug.zip?dl=0

It appears that AA is applied as though the surface is receiving decals, even when it isn't. Is it possible to work around this, as this makes decals under Forward Rendering, and MSAA borderline useless.

Product Version: UE 4.17
decalbug.png (350.3 kB)
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asked Aug 21 '17 at 09:00 PM in Bug Reports

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avatar image michaeleeli Feb 02 '18 at 06:35 AM

May I ask if you did any workarounds with this? Without MSAA my VR project just looks horrible, and not sure what to do that these artifacts are everywhere. This is happening to a lot of my regular opaque materials too.

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Hello Selentic,

Thank you for submitting a bug report. I have reproduced this issue and logged a report for it here


You can track the report's status as the issue is reviewed by our development staff. Please be aware that this issue may not be prioritized or fixed soon.

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answered Aug 22 '17 at 06:20 PM

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Thomas G ♦♦ STAFF
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