Training Stream - Tracing (Ray Casting) - Dec 20th - Live From Epic HQ

Ian and Alexander will be covering a number of ways available in Unreal Engine 4 to trace/ray cast. Tracing is an integral part of gaining information about the level, state of Actors, or even gaining a reference to an Actor at a location. Beyond this, shaped traces and traces that return everything they hit can be leveraged to determine anything from the number of walls around an object to a target location to if a character can fit through a gap.

Tuesday, December 20th @ 2:00PM ET Countdown]


Alexander Paschall - Community Manager - @UnrealAlexander](
Ian Shadden - Senior Technical Writer - @Shaddenfreude](


  • Ian feeling better already? we hope! or we just hoping he’ll be ok by the 20th?
    • OR was he abducted by aliens & they promised his return by the 20th?
      • We may never know!

But the streams ‘Must’ go On!

  • [MENTION=8]Alexander Paschall[/MENTION] will there be a stream the 22nd or is that too close to the holidays? or will there be a special stream with everyone wearing Reindeer Antlers n Santa Hats ? :cool:

** great to see this stream is going to happen btw, great subject that needs to be covered. always learning something from these streams. thx **

Thanks for offering this… If time allows can you please cover:

#1. Limitations of fast-moving spaceships tracking high-speed objects ahead. Special ‘CCD’ tracing needed?

#2. Multiplayer considerations: Tracing differences in single-player versus multiplayer: Origin-Rebasing etc.

#3. Tracing based on where the Player Camera is actually looking (equivalent of LOS Triggers in UDK etc).

Please could you go over the best practices of use, especially when it comes to which shape may best suit a specific task (e.g. why use a cylinder when a box would work). This may be specific to what you’re trying to achieve but a rough guide would be nice.

Also how expensive each trace is, since I’ve seen people claim on other forums/sites that now we have faster CPUs (than say back in UT '99’s day) trace expense doesn’t matter and to just go nuts with them, which I’ve never been 100% convinced about (from memory they were putting them all on Tick too).

[Question] How to manage materials/physical materials with raycast?

Great. This came at the right moment as I am currently making the design docs for a game that will heavely make use of raytraces. Will the training stream be focused on Blueprints ?

This stream will be OP.

Bringing this over from the last forum post:

Can you go over expense of each trace and how to find them in the profiler, as well as best practices of use. If there should be a hard limit to their use and if so, what other options are there available to us.

Ah, I didn’t find Ian’s Unreal Christmas Beanie in the Epic Store. :frowning:

Its a shame my questions from the previous thread about this event where not handled in the stream :frowning:

Next time please be more clear as to what date a stream is moving too, i stalked the forums for a week when that stream was cancelled to find out when the new one would be, and then yesterday randomly ran into the vid on youtube…