# Programming & Scripting **URL:** https://forums.unrealengine.com/c/development-discussion/programming-scripting/148.md?page=6 [Latest](https://forums.unrealengine.com/latest.md) · [Categories](https://forums.unrealengine.com/categories.md) · [Tags](https://forums.unrealengine.com/tags.md) **Page:** 7 --- ## [Object pooling in Unreal Engine Blueprint: stop spawn and destroy](https://forums.unrealengine.com/t/object-pooling-in-unreal-engine-blueprint-stop-spawn-and-destroy/2847158)
**Author:** [@BWGGames](https://forums.unrealengine.com/u/BWGGames)\ **Replies:** 0\ **Last updated:** [October 30, 2026, 2:52pm UTC](https://forums.unrealengine.com/t/object-pooling-in-unreal-engine-blueprint-stop-spawn-and-destroy/2847158 "2026-10-30T14:52:46Z")
Spawning and destroying the same projectile or hit effect on every shot repeats work a pool can skip. A pool keeps released actors hidden and reuses them. Steps in Blueprint: Where you call Spawn Actor from Class for a… --- ## [5.8 Localization Issue](https://forums.unrealengine.com/t/5-8-localization-issue/2847139)
**Author:** [@Origins](https://forums.unrealengine.com/u/Origins)\ **Replies:** 0\ **Last updated:** [October 30, 2026, 1:38pm UTC](https://forums.unrealengine.com/t/5-8-localization-issue/2847139 "2026-10-30T13:38:02Z")
(topic deleted by author) --- ## [Scene Graph: interactable mesh that players can walk through?](https://forums.unrealengine.com/t/scene-graph-interactable-mesh-that-players-can-walk-through/2847136)
**Author:** [@qw1z](https://forums.unrealengine.com/u/qw1z)\ **Replies:** 0\ **Last updated:** [October 30, 2026, 1:23pm UTC](https://forums.unrealengine.com/t/scene-graph-interactable-mesh-that-players-can-walk-through/2847136 "2026-10-30T13:23:17Z")
(topic deleted by author) --- ## [An open-source solution to easily download your owned Fab assets for any engine version, without needing to install a specific Unreal Engine version from the Epic Games Launcher.](https://forums.unrealengine.com/t/an-open-source-solution-to-easily-download-your-owned-fab-assets-for-any-engine-version-without-needing-to-install-a-specific-unreal-engine-version-from-the-epic-games-launcher/2847126)
**Author:** [@Fobal](https://forums.unrealengine.com/u/Fobal)\ **Replies:** 0\ **Last updated:** [October 30, 2026, 12:20pm UTC](https://forums.unrealengine.com/t/an-open-source-solution-to-easily-download-your-owned-fab-assets-for-any-engine-version-without-needing-to-install-a-specific-unreal-engine-version-from-the-epic-games-launcher/2847126 "2026-10-30T12:20:24Z")
Hello everyone! Here’s my custom solution to a long-standing problem: downloading and installing Fab Marketplace assets into a source-built Unreal Engine (and other setups). This tool makes it easy to download owned as… --- ## [Iris Replication System ](https://forums.unrealengine.com/t/iris-replication-system/2661726)
**Author:** [@Fin1kkk](https://forums.unrealengine.com/u/Fin1kkk)\ **Replies:** 1\ **Last updated:** [October 30, 2026, 11:40am UTC](https://forums.unrealengine.com/t/iris-replication-system/2661726 "2026-10-30T11:40:17Z")
Hello everyone, I recently watched an insightful Unreal Fest Orlando 2025 session about the development of Iris. My question is, how reliable is the system in the current experimental state? There’s more official docume… --- ## [Make static actor Iris replication failure non-fatal during WP cell unload ](https://forums.unrealengine.com/t/make-static-actor-iris-replication-failure-non-fatal-during-wp-cell-unload/2718054)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 4\ **Last updated:** [October 30, 2026, 11:37am UTC](https://forums.unrealengine.com/t/make-static-actor-iris-replication-failure-non-fatal-during-wp-cell-unload/2718054 "2026-10-30T11:37:37Z")
We found an replication issue described as follow, not sure if Epic has already found and fixed it: When a client unloads a World Partition cell while the server has in-flight replication data for a static actor in tha… --- ## [Assert triggered in Iris with FFastArraySerializer type combined with ReplicatedUsing ](https://forums.unrealengine.com/t/assert-triggered-in-iris-with-ffastarrayserializer-type-combined-with-replicatedusing/2678265)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 3\ **Last updated:** [October 30, 2026, 11:32am UTC](https://forums.unrealengine.com/t/assert-triggered-in-iris-with-ffastarrayserializer-type-combined-with-replicatedusing/2678265 "2026-10-30T11:32:17Z")
Hi, I’m seeing an issue where a replicating a type based on FFastArraySerializer in a UPROPERTY with ReplicatedUsing=OnRep\_Func asserts with Iris, in FFastArrayReplicationFragmentBase since the resultant replication fra… --- ## [Iris: Fast Array does not reliably remove items under certain conditions. ](https://forums.unrealengine.com/t/iris-fast-array-does-not-reliably-remove-items-under-certain-conditions/2666615)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 10\ **Last updated:** [October 30, 2026, 11:29am UTC](https://forums.unrealengine.com/t/iris-fast-array-does-not-reliably-remove-items-under-certain-conditions/2666615 "2026-10-30T11:29:40Z")
We are experiencing an issue where Fast Arrays do not reliably remove items that the Server has removed. This issue only manifests when using Iris replication, it does not occur when using “standard” replication. It also… --- ## [\[Iris\] Multiple Actors Having a Shared Sub-Object Dependency ](https://forums.unrealengine.com/t/iris-multiple-actors-having-a-shared-sub-object-dependency/2606452)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 7\ **Last updated:** [October 30, 2026, 11:24am UTC](https://forums.unrealengine.com/t/iris-multiple-actors-having-a-shared-sub-object-dependency/2606452 "2026-10-30T11:24:19Z")
A little background on how we got here I think is required, We’ve got a large shared inventory for the players. Each item is a unique UObject instance because it’s a lot easier to track state changes to a given object t… --- ## [Iris Replication of TWeakObjectPtr inside a struct ](https://forums.unrealengine.com/t/iris-replication-of-tweakobjectptr-inside-a-struct/2706941)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 5\ **Last updated:** [October 30, 2026, 11:21am UTC](https://forums.unrealengine.com/t/iris-replication-of-tweakobjectptr-inside-a-struct/2706941 "2026-10-30T11:21:34Z")
Hi, I have come across a nuance of Iris and would like to know if this is intentional or not, and subsequently what the intended pattern should be. If I replicate a TWeakObjectPtr inside an actor, this gets replicated… --- ## [Replicating FInstancedStruct with Iris](https://forums.unrealengine.com/t/replicating-finstancedstruct-with-iris/1948348)
**Author:** [@Nacho\_Abril](https://forums.unrealengine.com/u/Nacho_Abril)\ **Replies:** 1\ **Last updated:** [October 30, 2026, 11:18am UTC](https://forums.unrealengine.com/t/replicating-finstancedstruct-with-iris/1948348 "2026-10-30T11:18:54Z")
I know Iris is still experimental, but we wanted to give it a try. We got the warning (apart of many others like it) “LogIris: Warning: Generating descriptor for struct InstancedStruct that has custom serialization” bu… --- ## [\[Iris\] Struct replication lifetime condition ](https://forums.unrealengine.com/t/iris-struct-replication-lifetime-condition/2653599)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 4\ **Last updated:** [October 30, 2026, 11:16am UTC](https://forums.unrealengine.com/t/iris-struct-replication-lifetime-condition/2653599 "2026-10-30T11:16:15Z")
Hello, We’re working on implementing optimizations to bandwidth to reduce bandwidth and Iris TickClientConnections time and the most bandwidth cost comes from NPP’s sync and aux states. We’ve already switched NPP over t… --- ## [how is server-to-client bandwidth controlled in Iris in UE 5.5 ](https://forums.unrealengine.com/t/how-is-server-to-client-bandwidth-controlled-in-iris-in-ue-5-5/2675046)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 4\ **Last updated:** [October 30, 2026, 11:13am UTC](https://forums.unrealengine.com/t/how-is-server-to-client-bandwidth-controlled-in-iris-in-ue-5-5/2675046 "2026-10-30T11:13:31Z")
Hi Iris Networking friends! I’m doing some exploring around bandwidth control and total object replication cap when using Iris. I’m somewhat familiar with configuration of the AGameNetworkManager::UpdateNetSpeeds functi… --- ## [Iris UNetObjectFilter (custom dynamic filter) linker error](https://forums.unrealengine.com/t/iris-unetobjectfilter-custom-dynamic-filter-linker-error/2456805)
**Author:** [@kaiagan1](https://forums.unrealengine.com/u/kaiagan1)\ **Replies:** 6\ **Last updated:** [October 30, 2026, 11:10am UTC](https://forums.unrealengine.com/t/iris-unetobjectfilter-custom-dynamic-filter-linker-error/2456805 "2026-10-30T11:10:48Z")
Hi, Official documentation about Iris is rather sparse (and as I noticed in several instances, slightly outdated). Epic is very quiet about Iris, hopefully it won’t be silently abandonned as it is very useful for what I… --- ## [Iris Replication Filtering](https://forums.unrealengine.com/t/iris-replication-filtering/1924098)
**Author:** [@ShineOfMyMind](https://forums.unrealengine.com/u/ShineOfMyMind)\ **Replies:** 1\ **Last updated:** [October 30, 2026, 11:08am UTC](https://forums.unrealengine.com/t/iris-replication-filtering/1924098 "2026-10-30T11:08:03Z")
Hi all! I can’t figure out how to work with the “Iris Replication” system. I connected it using this article: Migrate to Iris in Unreal Engine | Unreal Engine 5.4 Documentation | Epic Developer Community . It seems to… --- ## [5.7 Iris Strategy ](https://forums.unrealengine.com/t/5-7-iris-strategy/2699685)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 4\ **Last updated:** [October 30, 2026, 11:05am UTC](https://forums.unrealengine.com/t/5-7-iris-strategy/2699685 "2026-10-30T11:05:16Z")
Hey folks, I wanted to ask a quick question about Iris in UE 5.7. Chiefly, what is the expectation for licensees when migrating from 5.6 to 5.7? For more context, we had some bugs when we enabled and tested Iris before… --- ## [Iris Replication with bNetLoadOnClient ](https://forums.unrealengine.com/t/iris-replication-with-bnetloadonclient/2704361)
**Author:** [@anonymous-edc](https://forums.unrealengine.com/u/anonymous-edc)\ **Replies:** 12\ **Last updated:** [October 30, 2026, 11:02am UTC](https://forums.unrealengine.com/t/iris-replication-with-bnetloadonclient/2704361 "2026-10-30T11:02:36Z")
Hi, We are in the process of converting our project to use Iris, but are having problems when bNetLoadOnClient is set. It would appear that when this is set, and the client spawns within relevancy range, the actor does… --- ## [Trying to enable Iris leads to crash: Assertion failed: ArraySerializer.IDCounter == 0 && ArraySerializer.ArrayReplicationKey == 0](https://forums.unrealengine.com/t/trying-to-enable-iris-leads-to-crash-assertion-failed-arrayserializer-idcounter-0-arrayserializer-arrayreplicationkey-0/2704931)
**Author:** [@JediKnightChan](https://forums.unrealengine.com/u/JediKnightChan)\ **Replies:** 2\ **Last updated:** [October 30, 2026, 10:59am UTC](https://forums.unrealengine.com/t/trying-to-enable-iris-leads-to-crash-assertion-failed-arrayserializer-idcounter-0-arrayserializer-arrayreplicationkey-0/2704931 "2026-10-30T10:59:48Z")
I tried to enable Iris in my game, which is originated from Lyra 5.1 template, I tried to do this both in 5.1 and in 5.2, where Iris is precompiled, but in both cases I got the following crash as soon as client tried to … --- ## [How can i enable Iris repliaction in Lyra](https://forums.unrealengine.com/t/how-can-i-enable-iris-repliaction-in-lyra/743410)
**Author:** [@489366](https://forums.unrealengine.com/u/489366)\ **Replies:** 3\ **Last updated:** [October 30, 2026, 10:57am UTC](https://forums.unrealengine.com/t/how-can-i-enable-iris-repliaction-in-lyra/743410 "2026-10-30T10:57:01Z")
I enable the Iris plugin in project but no effect, then followed the method in Getting Started with Iris Replication — Kia Armani but still not work. What is the correct way to enable Iris. --- ## [UE 5.8 Mover: LNK2001 when an external module constructs \`FLayeredMove\_AnimRootMotion\_SimDriven\` (missing \`MOVER\_API\` on \`OnStart\_Async\`)](https://forums.unrealengine.com/t/ue-5-8-mover-lnk2001-when-an-external-module-constructs-flayeredmove-animrootmotion-simdriven-missing-mover-api-on-onstart-async/2846990)
**Author:** [@2d131372ae0d4c71b3e7534e979d8228](https://forums.unrealengine.com/u/2d131372ae0d4c71b3e7534e979d8228)\ **Replies:** 0\ **Last updated:** [October 30, 2026, 6:41am UTC](https://forums.unrealengine.com/t/ue-5-8-mover-lnk2001-when-an-external-module-constructs-flayeredmove-animrootmotion-simdriven-missing-mover-api-on-onstart-async/2846990 "2026-10-30T06:41:56Z")
Summary In UE 5.8 (Experimental Mover plugin), constructing FLayeredMove\_AnimRootMotion\_SimDriven from a game or plugin module — e.g. MakeShared\(), exactly like the engine’s own UPl… --- ## [How to make EpicGamesLauncher know that I already have UE5.0.2 built from source?](https://forums.unrealengine.com/t/how-to-make-epicgameslauncher-know-that-i-already-have-ue5-0-2-built-from-source/567211)
**Author:** [@DarknessFX](https://forums.unrealengine.com/u/DarknessFX)\ **Replies:** 9\ **Last updated:** [October 30, 2026, 3:46am UTC](https://forums.unrealengine.com/t/how-to-make-epicgameslauncher-know-that-i-already-have-ue5-0-2-built-from-source/567211 "2026-10-30T03:46:39Z")
I have built UE5.0.2 from source and everything is working great! Now I want to get some marketplace assets but the launcher don’t recognize my UE5.0.2 build. My “dumb fix” for this problem is: Rename my Source fol… --- ## [Damage thresholds set in Geometry Collections are not reflected in components.](https://forums.unrealengine.com/t/damage-thresholds-set-in-geometry-collections-are-not-reflected-in-components/2702436)
**Author:** [@ssks1914](https://forums.unrealengine.com/u/ssks1914)\ **Replies:** 2\ **Last updated:** [October 30, 2026, 12:49am UTC](https://forums.unrealengine.com/t/damage-thresholds-set-in-geometry-collections-are-not-reflected-in-components/2702436 "2026-10-30T00:49:57Z")
I have a question about the Geometry Collection component. Even if i set a damage threshold on a Geometry Collection, it will remain at the default value on the component. This means I have to manually set all the dama… --- ## [Please give example to using Swizzle modifier in enhanced input component](https://forums.unrealengine.com/t/please-give-example-to-using-swizzle-modifier-in-enhanced-input-component/956686)
**Author:** [@william5642](https://forums.unrealengine.com/u/william5642)\ **Replies:** 6\ **Last updated:** [October 30, 2026, 12:15am UTC](https://forums.unrealengine.com/t/please-give-example-to-using-swizzle-modifier-in-enhanced-input-component/956686 "2026-10-30T00:15:47Z")
Learning the new input system I dont understand when I should use Swizzle, I know that it flip axis but when I should use it ? Thanks --- ## [UE 5.8.4 (Launcher install): C++ build fails with RulesError "FabToolset" after Fab plugin 0.0.22 is installed ](https://forums.unrealengine.com/t/ue-5-8-4-launcher-install-c-build-fails-with-ruleserror-fabtoolset-after-fab-plugin-0-0-22-is-installed/2846815)
**Author:** [@Akarh](https://forums.unrealengine.com/u/Akarh)\ **Replies:** 0\ **Last updated:** [October 29, 2026, 6:36pm UTC](https://forums.unrealengine.com/t/ue-5-8-4-launcher-install-c-build-fails-with-ruleserror-fabtoolset-after-fab-plugin-0-0-22-is-installed/2846815 "2026-10-29T18:36:30Z")
Hello Epic, Building C++ projects fails on my UE 5.8.4 (Epic Games Launcher install) whenever the Fab plugin (version 0.0.22) is installed. Without the plugin, the build works. ENVIRONMENT - Unreal Engine 5.8.4 (Build… --- ## [Game State, Game Instance & Game Mode. Which one to use for what?](https://forums.unrealengine.com/t/game-state-game-instance-game-mode-which-one-to-use-for-what/399795)
**Author:** [@c0ldpr0xy](https://forums.unrealengine.com/u/c0ldpr0xy)\ **Replies:** 17\ **Last updated:** [October 29, 2026, 6:30pm UTC](https://forums.unrealengine.com/t/game-state-game-instance-game-mode-which-one-to-use-for-what/399795 "2026-10-29T18:30:20Z")
I’m making a simple co-op multiplayer game. You complete a level by defeating X amount of enemies and then you move on to next level (stream or not). Where would be best to store the variable that determines if you won … --- ## [Unreal Engine 5.6.1 Continues to crash when running a MQTT connection.](https://forums.unrealengine.com/t/unreal-engine-5-6-1-continues-to-crash-when-running-a-mqtt-connection/2720619)
**Author:** [@AddisonCtrlDevs](https://forums.unrealengine.com/u/AddisonCtrlDevs)\ **Replies:** 1\ **Last updated:** [October 29, 2026, 6:29pm UTC](https://forums.unrealengine.com/t/unreal-engine-5-6-1-continues-to-crash-when-running-a-mqtt-connection/2720619 "2026-10-29T18:29:45Z")
Good Morning All! (Quick preface, I am running this project on 5.6.1 and am attempting to use the built in experimental MQTT plugin) I am still trying to learn and experiment with MQTT implementation within UE5 bluepri… --- ## [I need a solution to a problem in UEFN, please. ](https://forums.unrealengine.com/t/i-need-a-solution-to-a-problem-in-uefn-please/2846795)
**Author:** [@EL\_MARGINAL](https://forums.unrealengine.com/u/EL_MARGINAL)\ **Replies:** 0\ **Last updated:** [October 29, 2026, 6:29pm UTC](https://forums.unrealengine.com/t/i-need-a-solution-to-a-problem-in-uefn-please/2846795 "2026-10-29T18:29:05Z")
"When testing my map via UEFN, the ice and sliding mechanics work perfectly. However, once I publish the version and access it in the standard version of Fortnite using the island code, the ice physics and sliding stop w… --- ## [UE5.1 Expecting to find a type to be declared in a module rules named '......'](https://forums.unrealengine.com/t/ue5-1-expecting-to-find-a-type-to-be-declared-in-a-module-rules-named/741811)
**Author:** [@Roy\_Wierer.Seda145](https://forums.unrealengine.com/u/Roy_Wierer.Seda145)\ **Replies:** 16\ **Last updated:** [October 29, 2026, 6:24pm UTC](https://forums.unrealengine.com/t/ue5-1-expecting-to-find-a-type-to-be-declared-in-a-module-rules-named/741811 "2026-10-29T18:24:57Z")
Compilation error: Expecting to find a type to be declared in a module rules named ‘DlssUtility’ in UE5Rules, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null. This type must derive from the ‘ModuleRules’ type def… --- ## [TextureGraph inputs disconnect after closing the graph](https://forums.unrealengine.com/t/texturegraph-inputs-disconnect-after-closing-the-graph/2845037)
**Author:** [@fx.anorak](https://forums.unrealengine.com/u/fx.anorak)\ **Replies:** 4\ **Last updated:** [October 29, 2026, 5:31pm UTC](https://forums.unrealengine.com/t/texturegraph-inputs-disconnect-after-closing-the-graph/2845037 "2026-10-29T17:31:59Z")
Hello there! I have tried to add Scalars as inputs to a Levels node and then save the Graph. When I open it again, it then seem to be disconnected. Am I doing something wrong or is this a bug? Best regards, fx\_an0rak … --- ## [Urgent help needed, university project keeps crashing and its due soon. Any help greatly appreciated! ](https://forums.unrealengine.com/t/urgent-help-needed-university-project-keeps-crashing-and-its-due-soon-any-help-greatly-appreciated/2846351)
**Author:** [@FritzEatsFries](https://forums.unrealengine.com/u/FritzEatsFries)\ **Replies:** 1\ **Last updated:** [October 29, 2026, 3:51pm UTC](https://forums.unrealengine.com/t/urgent-help-needed-university-project-keeps-crashing-and-its-due-soon-any-help-greatly-appreciated/2846351 "2026-10-29T15:51:25Z")
Trying to launch my university project on my laptop through git repo and fork but the engine crashes before it even opens, any idea how to fix it? This is what the error message gives me: Unhandled Exception: 0x80000003 … [Previous page](https://forums.unrealengine.com/c/development-discussion/programming-scripting/148.md?page=5) [Next page](https://forums.unrealengine.com/c/development-discussion/programming-scripting/148.md?page=7)