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"

Question about the physic materials in UE4

I have several questions regards the physics properties in a physics-material:

  • Friction

  • Friction combine

  • Restitution

I know that a friction of zero is like super glue where you cannot move at all, 100% energy lost in the tangential normal direction and one is like ice without any energy lost in the tangential normal direction too (Is that right?)

I know that restitution determines the bounciness of a body - zero means no bouncy at all, one means 100% bouncy without any energy lost in the normals direction (Is that right?)

I assume that friction combine, do what the names says... how the final friction value are calculated in a collision response for two rigid bodies.

What i dont know, how does UE4 calculates the "Final" Restitution Value (is it the maximum, the minimum or some average?

What friction values must i set for a static and a dynamic body, so that the dynamic do bounce 100% in a physical matter, without any energy lost and with a reflected velocity, but never ever slides along the static body?

Is there a way i can have multiple physical materials and switch based on a "On Overlap Actor" collision, so that i can have physical materials for different actors?

Thanks in regards, Finalspace

Product Version: Not Selected
Tags:
more ▼

asked Sep 09 '14 at 05:18 PM in Using UE4

avatar image

Finalspace
13 5 5 9

avatar image Pierdek Sep 09 '14 at 05:22 PM

I know that a friction of zero is like super glue where you cannot move at all, 100% energy lost in the tangential normal direction and one is like ice without any energy lost in the tangential normal direction too (Is that right?)

Nope, friction = 0, is like ice.

avatar image PersnicketyGareth Apr 27 '15 at 02:11 AM

I know that restitution determines the bounciness of a body - zero means no bouncy at all, one means 100% bouncy without any energy lost in the normals direction (Is that right?)

With restitution, the energy is first converted to what I think is called elastic potential, where the objects squish together, and then after that it is converted back into kinetic energy. The coefficient of restitution determines how much kinetic energy is lost to sound or whatever, and then that remaining energy is split in half between the two objects (unless one is static, in which case the mobile one gets all the remaining energy).

(comments are locked)
10|2000 characters needed characters left
Viewable by all users

1 answer: sort voted first

The restitution combine mode is to take the average. We haven't exposed this to the editor yet, but if there's a use case for it it would be fairly simple to add.

friction of 0 is like ice.

more ▼

answered Sep 09 '14 at 06:20 PM

avatar image

[Epic]Ori Cohen STAFF
1.4k 25 14 59

avatar image PompeyPaul Apr 14 '15 at 09:23 AM

It would be good to get it exposed. It can be useful to have an object, whose bounciness is set to 1 with bounce combine as multiply. It's then trivial to have a world material "NoBounce" whose restitution is 0 and the object hit's it and gets no bounce. You can then have a world material "Bouncy" and set it's restitution to 1 and get a bouncy world material. Using multiplies makes this set up more complicated. Bouncy becomes a restitution of 2, non bouncy remains 0 and the object has a restitution of 0. I.e. it's nice to have multiply so that object always takes the bouncing surface's restitution.

avatar image [Epic]Ori Cohen STAFF Apr 14 '15 at 01:55 PM

This has been exposed and will be available in 4.8

(comments are locked)
10|2000 characters needed characters left
Viewable by all users
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