frame-rate

Testing & Quality

Diagnose and remove FPS caps so the editor and game run uncapped (or at a target FPS). Use when the user says the editor/game is "locked", "capped", or "stuck" at a frame rate (commonly 60 FPS), asks to "unlock"/"uncap"/"raise" FPS, or wants to set a max FPS. Covers t.MaxFPS, VSync, fixed/smoothed frame rate, and background CPU throttling (EngineSettingsService).

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Source SKILL.md: https://github.com/kevinpbuckley/VibeUE/blob/HEAD/Content/Skills/frame-rate/SKILL.md

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Frame Rate / FPS Caps Skill

A "locked at 60 FPS" editor or game is almost never caused by a single setting — there are five independent caps and any one of them holds the frame rate down. Check and clear them all, in this order, before declaring it fixed.

⚠️ Diagnose first — don't guess

t.MaxFPS = 0 already means uncapped, so if the editor is still stuck at 60 the cap is coming from somewhere else (usually VSync to a 60 Hz monitor, or the smoothed frame-rate range). Read every source below before changing anything.

🩺 "Capped" vs "slow" are different problems. If the frame rate is low rather than pinned at a round number, it's not a cap — it's a workload. Run unreal.PerformanceService.frame_timing() first (NEW service that replaced the removed editor_control tool) for a CPU-vs-GPU-bound verdict before touching any cap below. The caps here only matter when something is artificially holding FPS down. (Cvar/INI reads/writes in this skill stay on EngineSettingsService.)

#	Setting	Where	"Uncapped" value
1	`t.MaxFPS`	cvar	`0` (or a high target like `240`)
2	`r.VSync` / `r.VSyncEditor`	cvar	`0` — locks to monitor refresh (60 Hz) when `1`
3	`bUseFixedFrameRate` / `FixedFrameRate`	`[/Script/Engine.Engine]` DefaultEngine.ini	`False`
4	`bSmoothFrameRate` / `SmoothedFrameRateRange`	`[/Script/Engine.Engine]` DefaultEngine.ini	`False` — the usual ~60 editor cap
5	`bThrottleCPUWhenNotForeground`	`[/Script/UnrealEd.EditorPerformanceSettings]` EditorPerProjectUserSettings.ini	`False` — caps FPS when the editor isn't focused

Note: r.FrameRateLimit is not a console variable in UE 5.7 — set_console_variable will report "Console variable not found". The INI key is FrameRateLimit under [/Script/Engine.Engine], but t.MaxFPS is the reliable runtime cap.

Workflow — read the current state

import unreal
es = unreal.EngineSettingsService

for cvar in ["t.MaxFPS", "r.VSync", "r.VSyncEditor"]:
    print(f"{cvar} = {es.get_console_variable(cvar)}")

eng = "/Script/Engine.Engine"
for key in ["bUseFixedFrameRate", "FixedFrameRate", "bSmoothFrameRate", "SmoothedFrameRateRange"]:
    print(f"{key} = {es.get_engine_ini_value(eng, key, 'DefaultEngine.ini')!r}")

print("bThrottleCPUWhenNotForeground =",
      es.get_engine_ini_value("/Script/UnrealEd.EditorPerformanceSettings",
                              "bThrottleCPUWhenNotForeground", "EditorPerProjectUserSettings.ini"))

Workflow — uncap FPS

Set a target with t.MaxFPS (use 0 for fully uncapped, or e.g. 240 to cap high), then clear the other four caps. cvars take effect immediately; INI changes need a save and may require an editor restart.

import unreal, json
es = unreal.EngineSettingsService

TARGET_MAX_FPS = "240"   # "0" = fully uncapped

# 1 + 2: runtime cvars (immediate)
es.set_console_variables_from_json(json.dumps({
    "t.MaxFPS":     TARGET_MAX_FPS,
    "r.VSync":      "0",
    "r.VSyncEditor":"0",
}))

# 3 + 4: disable fixed and smoothed frame-rate caps (persisted to ini)
eng = "/Script/Engine.Engine"
es.set_engine_ini_value(eng, "bUseFixedFrameRate", "False", "DefaultEngine.ini")
es.set_engine_ini_value(eng, "bSmoothFrameRate",   "False", "DefaultEngine.ini")

# 5: don't throttle FPS when the editor loses focus
es.set_engine_ini_value("/Script/UnrealEd.EditorPerformanceSettings",
                        "bThrottleCPUWhenNotForeground", "False",
                        "EditorPerProjectUserSettings.ini")

es.save_all_engine_config()
print("FPS caps cleared. t.MaxFPS now:", es.get_console_variable("t.MaxFPS"))

Verify

After applying, confirm t.MaxFPS reads your target and the editor's FPS overlay (Show FPS, or stat fps in PIE) climbs past 60. If it's still pinned at 60, the most likely remaining cause is r.VSync/r.VSyncEditor re-enabled by a quality preset, or the monitor itself — VSync can only go as high as the display refresh rate.

Sample scripts (run via `execute_python_code`)

scripts/uncap_fps.txt — read all five caps, then uncap to a target FPS.