Epic notes that "Steam now handles friends, matchmaking and server browsing in the UDK," the same systems that are used in Valve's Team Fortress 2 and Left 4 Dead.

Other new features include support for Scaleform's Flash-based user interfaces, attractive new light shafts and fog, performance improvements, tweaks and fixes. The full changelog for the May 2010 Unreal Development Kit beta follows below.

Scaleform GFx

• Scaleform is now supported in UnrealEd and in-game! (watch video)
• Supports
• UI screens
• Dynamic interaction via UnrealScript or Kismet
• SWFs playing into dynamic render targets
• GFx version of UDK HUD, scoreboard and pause menu now fully functional
• Added example Adobe Flash Studio files to UDKGame/Flash/example/...
• Controller input setup for GFx movies
• Basic scene using Scaleform CLIK components to create a UI
• Files
• New GFx import path
•  Textures used by SWF movies imported from original art
•  Current import path is not final; subject to change!
• More details.
• Started implementing localization for GFx menus
• Additional documentation.

Steam

• Steam is now the default OnlineSubsystem for UDKGame Win32
• Steam now handles friends, matchmaking and server browsing in the UDK

Light Shafts

• Point Lights are now supported
• Added Bloom Threshold and BloomTint properties
• Documentation.

Exponential Height Fog

• New kind of global fog with density that decreases with height
• Never creates a hard line (unlike standard fog); supports one layer
• Can specify both "towards the light" and "away from the light" colors
• Rendering cost similar to two layers of constant density height fog
• Can now use different colors for the hemisphere facing the light and vice versa

Color Grading Blending

• Can now blend between different color LUTs on different post process volumes!
• Documentation.

Editor

• UDK now supports running 64-bit binaries for the editor
• Added 'search by object' type to Kismet
• New mesh emitter camera facing option: "Apply Particle Rotation As Spin"
• Editor now shows up in system tray while starting up (and Alt+Tab works!)
• Can now capture content browser thumbnails from PIE viewports
• Added ability to tint editor icons similar to Point Lights
• PNGs can now be imported as textures; RGB and RGBA formats are supported
• Viewports
• New Alt+F/G/H/J shortcuts to switch between viewport types
• Greatly reduced the time it takes for volume visibility updates

Installer

• Now being localized for
• INT - English
• FRA - French
• ITA - Italian
• DEU - German
• ESN - European Spanish
• ESM - Latin American Spanish
• RUS - Russian
• HUN - Hungarian
• CZE - Czech
• SLO - Slovakian
• POL - Polish
• JPN - Japanese
• CHN - Simplified Chinese
• KOR - Korean

Editor Fixes

• Materials can no longer be placed as decals unless the decal usage flag is set
• Fixed fog volumes being created when dropping materials sometimes
• Fixed support for non-standard languages

FBX Importer

• Added support for rigid animation!
• FBX import settings are now remembered between sessions
• Importer will detect the type of asset to import by peeking at the FBX file
• New import option to override naming of imported assets
• Textures can now be imported (with or without a material being created)
• The FBX import dialog has been improved
• Updated to the latest FBX SDK (2011.2)
• Can now re-import skeletal meshes from FBX files
• Fixed smoothing group warning dialog spam on mesh import

UDKGame

• Scaleform / UI
• Added (prototype) Scaleform-based front end and HUD to UDKGame
• Added GFx example content to ExampleMap
• Scaleform implementations of HUD, Pause Menu, Scoreboard
• Code clean-up
• Moved UT-specific functionality from Weapon to UTWeapon.
• Moved HUDIcons and HUDCoords properties from UDKVehicleBase to UTVehicle
• Cleaned up UDK default engine.inis down to two
• Moved DeathTime from UDKPawn to UTPawn
• Removed unused UDKPawn property LookYaw
• Removed PlayFiringSound() call from Weapon.FireAmmunition() (not implemented for any game except UTGame)
• Moved bio death material effect system from UDKPawn to UTPawn
• Enabled tone mapping and color grading support to UDK
•  Enabled by default now so all scenes will receive contrast-enhancing tone mapping
• Misc
•  Changed input handling of controller demo to not recurse, therefore stopping the CLIK button from swallowing the GAMEPAD_A event
• Spawn player as spectator if ?causeevent=flythrough is passed on the commandline
•  Set bFixedPlayerStart=true, bForceRespawn=true, and bQuickStat=true if ?causeevent=flythrough is passed on the commandline

Swarm

• Fixed several issues related to version numbers and matching Agents to Jobs
• Change usage of "localhost" to using the localhost IP address (127.0.0.1) instead

Gameplay Profiler

• Replacing old UE2 ueScriptProfiler
• Adds ability to drill into actor and component tick
• Documentation.

Attachment Editor

• Draw bone/socket label on connector for actors attached to skeletal meshes
• Allow nodes to be manually moved around
• Allow attachments to be made in a more 'Kismet like' way

NavMesh

• Lots of runtime navmesh optimizations (mostly related to dynamic submesh builds)
• Huge speed gains

AnimSet Viewer

• Added copy and paste animations to the AnimSet browser
• New options for calculating Bone Break
• Default: Both meshes have to influence to use rigid
• Auto Detect Rigid: Detects rigid when soft body misses the weight
• Alternate weight preferred: Second weight has more priority
• Added "Delete selected bone weighting" option
• "Toggle Mesh Weights" option
• Displayed if there is a valid set of weights for the current LOD
• Otherwise, the option is disabled
• Added info to display chunks/sections when swapping vertex weights

Max Quality Mode

• Added MaxQualityMode option for taking high-resolution screenshots
• Increases texture res and shadow quality regardless of performance

Property Multi-Select and Cut-Paste

• Control-Click on properties to add to selection
• Control-C, Control-V or right click to copy and paste!

Lighting Changes

• Improved unbuilt lighting performance
• Changed bUseBooleanEnvironmentShadowing to default to TRUE for best performance
• Light environments will not receive dynamic shadows from the static environment unless bUseBooleanEnvironmentShadowing is changed back to false!
• Primitives with bShadowIndirectOnly=true no longer cast dynamic shadows
• Added bForceNoPrecomputedLighting to WorldInfo, allowing maps with fully dynamic lighting to skip time-consuming light building during a full rebuild
• Hid light environment settings that are rarely used, edge cases, or only set by gameplay code to simplify the interface

Scene Capture Optimizations

• 'Max View Distance Override': Set a culling distance for objects rendered into the reflection
• 'Skip Update If Owner Occluded': Skip rendering to the scene capture entirely if it's not going to be visible
• 'Skip Rendering Depth Prepass': Controls whether a depth prepass is performed when rendering the scene capture
• Capture will be culled if last-bound time of the render target texture is more than a second ago

Rendering

• Added map check warning for large shadow casters unless they have bAcceptsDynamicDominantLightShadows=false
• New mesh emitter camera facing option: bApplyParticleRotationAsSpin
• Changed bRenderAsVelocity to default to TRUE for RadialBlurComponents as they are much faster to render this way
• Mesh area lights now affect dynamic objects!
• UE3 creates a spotlight at the center of the emissive area which is applied to dynamic objects
• Added a new volume type: LightmassCharacterIndirectDetailVolume
• Lightmass generates higher density indirect character lighting samples inside these volumes
• Useful for sections where characters are not over static ground, e.g., elevators
• Using down-sampled scene texture for depth of field, bloom and motion blur  Documentation.

Warnings

• Exporting TGAs is temporarily broken and results in weird interlaced images

Upcoming changes (as of the next UDK build)

• SM2 support will be removed