I would like to know how to leave a fading texture/material trail in udk.

For example (I'm not sure if there is a special name for this effect):

  • A character may leave footprints that fade after x number of seconds
  • Or, a tank may leave a tracks trail as in Civilization IV.

Here is another example of this type of effect. Skip to 1:00 and watch the green slime texture.


How do I accomplish this effect in UDK? Any good tutorials?

Thank you.


1 Answer 1


I haven't used UDK before, but I'm sure it supports a texture alpha channel. In order to fade a texture out over time, you just update it's alpha channel based on the amount of time elapsed since it was placed. For example:

if(time >= 10000 && time <= 20000)
    texture.alpha = 1 - ((20000 - time)/10000);

Where time is the time elapsed since the texture was placed and is stored in milliseconds. This will start fading the texture after 10 seconds (10,000 milliseconds), and fade for 10 seconds until it's completely faded. I'm not sure it's that what you're looking for :/

This page seems like it has good information on texture painting and alpha. And a video here.

  • \$\begingroup\$ Thanks for taking the time to look at my question, Byte. However, your answer isn't quite what I'm looking for. I believe now, that it may be done through the particle system or the new decals for UDK Landscape. \$\endgroup\$
    – kdshay
    Jun 28, 2011 at 15:54
  • \$\begingroup\$ Ah, you wanted to know more about placing them, not making them fade. Sorry. \$\endgroup\$
    – House
    Jun 29, 2011 at 0:35

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