Viewport draw errors with Sky+Fog+AA on UE 4.9 on iMac

Hey, here are few images displaying in the graphics error on viewport with UE 4.9 and 4.9.1.
The error patterns flickers wildly.

EDIT: Forgot to mention that UE 4.8.3 is without these errors on the same system. So I’m assuming it’s happening only because some changes in 4.9.

System is iMac late 2011, with Intel Core i7 / AMD Radeon HD 6970M 1024 MB

SKY+FOG, with AA
SKY only, with AA

FOG only, with AA

SKY+FOG without AA

Hey jamov,

Another user is reporting this issue as well, on a very similar system. We are currently attempting to gather the correct components to create a machine to test this issue and others against. I tested on the Mac we have here and did not receive the visual errors you and the other user are experiencing.

The machine I tested on however, is using and Nvidia 750M card, and not an AMD GPU which is what is needed when testing to get an accurate repro. If you discover any new information please let me know.

As a temporary workaround you can try to switch to FXAA instead of Temporal AA to see if that resolves the issue.

Thank you,

Andrew Hurley

I have the same issue, contact me if you need to do some testing

@Artymandis Would you provide me with your systems specifications so I can compare it to other users experiencing the issue?

Here the basic info. It’s in french but should not be an issue. It’s mid-2011 21.5 iMac

Nom du modèle : iMac
Identifiant du modèle : iMac12,1
Nom du processeur : Intel Core i5
Vitesse du processeur : 2,5 GHz
Nombre de processeurs : 1
Nombre total de cœurs : 4
Cache de niveau 2 (par cœur) : 256 Ko
Cache de niveau 3 : 6 Mo
Mémoire : 8 Go
Version de la ROM de démarrage : IM121.0047.B21
Version SMC (système) : 1.71f22

AMD Radeon HD 6750M :

Jeu de composants : AMD Radeon HD 6750M
Type : Processeur graphique (GPU)
Bus : PCIe
Longueur de la voie PCIe : x16
VRAM (totale) : 512 Mo
Fournisseur : ATI (0x1002)
Identifiant du périphérique : 0x6741
Identifiant de révision : 0x0000
Révision de la ROM : 113-C2950H-175
Version du gestionnaire EFI : 01.00.560
Moniteurs :
iMac :
Type de moniteur : LCD
Résolution : 1920 x 1080
Profondeur de pixels : Couleurs 32 bits (ARGB8888)
Moniteur principal : Oui
Miroir : Désactivé
Connecté : Oui
Intégré : Oui
90GX2 :
Résolution : 1280 x 1024 @ 60 Hz
Profondeur de pixels : Couleurs 32 bits (ARGB8888)
Numéro de série du moniteur : 5Z004192GA
Miroir : Désactivé
Connecté : Oui
Rotation : Géré

I can send you the whole report, but I will need an email or another way to send you the file

Thank you for providing me with the information as requested. A bug has been entered for this issue (UE-21214).

You seem to be sharing a very similar machine to the user who is reporting this issue, which is a helpful hint as where to look for the source of the issue. When a fix for this issue has been implemented, it will be added to the Hotfix or Major Release notes which you can find on our Documentation page or our Forums.

If you have further questions please let me know.

Thank you,

Andrew Hurley

Thank you for the reply, and thanks to the team for handling the issue. Looking forward to seeing the update soon.