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What to do: Particle System Emitter effects disappear when camera not facing emitter

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    What to do: Particle System Emitter effects disappear when camera not facing emitter

    Dear Community,

    I could not find any help for this online after hours of searching, so I am creating a tutorial on this subject!


    Your very pretty PhysX or regular particle system emitter effects disappear from the world when the camera is not facing the emitter source.

    For PhysX particles that last more than a couple seconds this is especially obvious because they might fall or move a great distance from the emitter, and if player turns to look at them, away from the emitter source,


    they disappear!

    The particles will reappear if camera turns back to face the emitter source.

    But how to enable player to see the particles even if not looking at the emitter source?


    The Solution

    Here's the solution I found, so that the particles will stay visible even if player is looking 180 degrees away from the emitter source.

    The issue is one called Occlusion, the particles that fall far away from the emitter are still considered part of the emitter, and in an effort to conserve resources the engine is occluding, or removing the emitter if it is not visible to the camera....including the particles that have fallen a great distance.

    In the UDK you can set the bounds of the emitter to be HUGE, so that the player is literally inside the bounds of the emitter, and this means that the emitter will never be occluded, at least not for a absolutely large distance, and so the particles will be rendered even if player is looking far away from the source of the explosion.


    In the UDK

    Step 1: Right-click on your Particle System -> Properties (near top of right-click menu)

    Step 2: find the section called Bounds

    Step 3: make sure "use fixed bounds" is checked

    Step 4:

    for min values

    x -100000
    y -100000
    z -100000

    for max values

    x 100000
    y 100000
    z 100000

    note that the min values must be negative, to make the box that serves as the new bounds of the emitter

    now your emitter will likely NEVER be occluded so your lovely particles will be visible to the player camrea in full 360 degrees in any direction from the emitter source


    Performance issues

    Use a number smaller than 100000 if you actually do want to occlude the particles and the emitter at certain distance, numbers like 3000 are probably reasonable.

    I used 100000 cause I absolutely want to always see the particles and it is a single player game so performance is not an issue with this set up.


    Hope This Helps

    Let me know if this helps you!


    So if i face a fire fx i'll see it but if i turn the camera of 180° it will disappear ? It would boost fps in-game alot, gonna try it thanks


      That's the normal behavior yes, if you set the bounds of the emitter to be small (32x32x32 for example), which they normally are.

      check your bounds on your emitter, if they are small numbers, then this is already happening

      but if you want the effect to STAY visible, use very large numbers