x

Search in
Sort by:

Question Status:

Search help

  • Simple searches use one or more words. Separate the words with spaces (cat dog) to search cat,dog or both. Separate the words with plus signs (cat +dog) to search for items that may contain cat but must contain dog.
  • You can further refine your search on the search results page, where you can search by keywords, author, topic. These can be combined with each other. Examples
    • cat dog --matches anything with cat,dog or both
    • cat +dog --searches for cat +dog where dog is a mandatory term
    • cat -dog -- searches for cat excluding any result containing dog
    • [cats] —will restrict your search to results with topic named "cats"
    • [cats] [dogs] —will restrict your search to results with both topics, "cats", and "dogs"

Unexpected behavior: Sin(time) seems to be "invisibly" remapped

Hi, there! This is a quick, and maybe pedantic question about the Sin and Time nodes in Unreal, but I'm experiencing some odd behavior that I'd like to better understand.

In this screen recording, I have a simple material set up with sin(time) going into the opacity channel (after being remapped from -1,1 to 0,1) -- and the odd thing is, that produces an oscillation with a period of one second.

In my mind, the expected behavior would be a period of 2π, or 6.28 seconds, because the sin node receives an input in radians and the default period of a sin operation is 2π. Meanwhile, when I try to multiply the Time node output by 2π / PERIOD PARAMETER in the video (which is what I would think to do in order to create a cleanly parameterizable period), I get an oscillation with 2π oscillations per minute.

So, what's going on here? Does the sin node somehow "know" that it's receiving a time input and trigger some special remapping behavior? Is my time input just operating on a 2π-multiplied scale? This isn't necessarily a blocker, but if there's some predetermined behavior I'd like to know how it works and be able to work around it

Much thanks! Brendan

Product Version: UE 4.17
Tags:
more ▼

asked Sep 11 '17 at 10:40 PM in Rendering

avatar image

BrendanLoBuglio
16 1 3

(comments are locked)
10|2000 characters needed characters left

1 answer: sort voted first

This is definitely an intended behavior.

more ▼

answered Sep 11 '17 at 10:59 PM

avatar image

Deathrey
7.6k 129 28 289

avatar image BrendanLoBuglio Sep 15 '17 at 10:58 PM

Hi, Deathrey! I agree that it totally seems intended, but my question is more with regard to the way that this is implemented -- whether this happens only if the Time is directly hooked up to a Sin node or if Time -> arbitrary node -> Sin also works, whether there are other nodes that have custom behavior with Time input or sin output, and other things of that nature.

It's obviously a nice convenience, but invisible behaviors like these can be dangerous if you don't 100% understand them. Ultimately, I wish there was some documentation!

(comments are locked)
10|2000 characters needed characters left
Your answer
toggle preview:

Up to 5 attachments (including images) can be used with a maximum of 5.2 MB each and 5.2 MB total.

Follow this question

Once you sign in you will be able to subscribe for any updates here

Answers to this question