How To Make Something Call To Diferent Animations Ue4

Choosing what collides is obviously very important, simply it tin can exist tricky, and information technology'due south a problem that we have spent quite a while discussing while developing UE4. The system we have can seem a little circuitous at outset, but information technology is very powerful and consequent, so I wanted to give a little background on how we arrived at it. We'll talk about the different responses to collision, how nosotros use channels to filter collisions, and outline the departure between elementary and complex standoff geometry.

Blocking, Overlapping and Ignoring

The commencement matter to know is that when you say something should collide, you lot have to choose whether you can penetrate information technology or not. A brick wall volition 'Block' a player, just a trigger will 'Overlap' them, assuasive them to laissez passer through. Both generate an result ('Hitting' or 'Overlap' respectively, in UE4 terminology) but it is an important difference*. Other objects may 'Ignore' the collision altogether, giving us our iii response types.

Trace Channels and Object Channels

The next big question at the heart of standoff filtering is "who gets to choose?" Is it the object that decides what types of query to collide with? Or does the query make up one's mind what types of object information technology is looking for? In different scenarios they both make sense, and so UE4 supports both!

Imagine we define two 'Trace Channels' in our game, one for 'Visibility' and ane for 'Weapon' queries. A brick wall is set to block both, a shrub blocks visibility but not weapons, and bulletproof glass blocks weapons simply not visibility. When you exercise this kind of query you lot specify a unmarried Trace Channel.

If I changed this around so the game code had to know what types of object to query for, our game could need a huge number of dissimilar types to handle all these situations! Information technology also allows usa to make 'spot fixes' in content subsequently on, instead of changing the calling code itself and possibly breaking other things.

In that location are still some situations where you exercise want to query for objects based purely on their type, and this is where we use 'Object Channels'. 1 instance is an explosion going off, and you desire to apace find all objects of type 'Pawn' or 'PhysicsBody' within a certain radius. When y'all practice this kind of query, yous can specify multiple Object Channels.

UE4 has a few 'built in' Trace Channels (Visibility, Camera) and Object Channels (WorldStatic, WorldDynamic, Pawn, PhysicsBody, Vehicle, Destructible), only y'all tin easily add your ain under Edit -> Project Settings -> Standoff, though y'all are limited to 32 in full.

Collisions Between Moving Objects

Things get a bit more complicated when you want to handle collisions between moving objects, because there can be then many combinations. In UE4 each object knows its ain Object Aqueduct, plus a list of how information technology responds to other Object Channels. When two objects intersect, we wait at how they respond to each other, and have the least blocking interaction, like and so:

Then imagine the following scene:

Now the player moves forrard. First he will overlap the shrub. The Player is of type Pawn, and the Shrub wants to Overlap that. The Shrub is of type WorldStatic, and the Player wants to Block that. Checking the nautical chart, the last result is Overlap! Similarly the Brick Wall and Player both want to Block each other, so the player walks through the Shrub (generating an Overlap result) and is stopped by the wall (generating a Hit effect).

If you had two players and one wanted to become 'ghostly', he could change his response to the Pawn aqueduct from Cake to Ignore, and and then he could walk right through other players.

Collision Presets

Fifty-fifty though this arrangement gives a lot of control over what objects in your level will collide with, in practise most objects fall into common configurations. To make things easier, UE4 has a 'Standoff Preset' system. Each Preset contains an Object Blazon, and a response to each Trace and Object Channel in your game. When y'all select an object in the level, yous will come across a unproblematic dropdown, allowing y'all to select a Preset:

UE4 has several of these built in (eastward.g. Invisible Wall, Physics Actor etc), and over again yous can create your own inside Project Settings. If you don't want to employ a Preset, you tin choose 'Custom…' and and then you can alter every response, liked we talked most above:

Elementary and Circuitous Collision

I terminal thing to understand is that each object in UE4 can take both a 'complex' and 'unproblematic' collision representation. Complex Collision refers to using the actual rendering geometry for collision. This is nearly useful for things similar weapon traces, where you want to be able to shoot exactly what you run into. Yous don't always want to collide with this though, and so each mesh can likewise accept a Simple Collision representation consisting of a collection of spheres, boxes, capsules and convex hulls. When you perform a collision query, you lot tell UE4 what kind of geometry you desire to collide with. Player motility, for case, collides against unproblematic geometry, to avoid getting 'stuck' on lilliputian details.

In the editor in that location is a handy View Mode that lets you see the world equally a player volition collide with it:

Conclusion

So that is the whole, heady globe of collision filtering in UE4! I promise information technology was helpful to understand some of the bug nosotros are trying to solve and how to make employ of information technology for your own game. Whatever questions or comments? We're always over in the forums or you can hitting me up on Twitter at @EpicJamesG.

--

*We can actually stop looking for collisions after the first blocking collision, which is a good performance optimization - imagine firing a gun with a range of 1km at a brick wall 1m in front of y'all, we just skipped 999 meters of work!

Source: https://www.unrealengine.com/en-US/blog/collision-filtering

Posted by: tedescobutibill79.blogspot.com

Share this post