So to do this we just simply subtract the Blueprint origin location from the Hit Location to get the difference, which is the Local offset. SetRelativeLocation: We only want to move the Cube relative to the origin of the Blueprint, but we have the World Space location of the Hit. There's lots of data available but all we really need to get is the Location of the hit, which is returned in World Space. We've talked about Structs earlier in the Data Types lesson but all we need to know here is that we have to Break it to get to the data inside. If we didn't hit anything, then we don't want to do anything so we can just leave the False pin blank.īreak Hit Result: The other output pin from a Line Trace is a custom Struct with all the information about the Trace that we might need. Note the Debug Draw Type options - this doesn't work very well in the Construction Script but when we get to using these in game this will give a very useful preview of the line being cast.īranch: The line trace node outputs a Boolean value depending on if the trace was successful or not, ie, did the trace hit anything. We could use a Vector or, as we're doing here, just do Vector + Vector and break the second Vector and plug a Float Parameter into the Z. To just check straight down we just need to take away a value from the Z component of the world space vector. GetActorLocation: By getting the location of the DefaultSceneRoot we're getting the location of the Blueprint in the world - great, that's the start location of our line trace. There's also the option for a SphereTrace where the engine moves a Sphere along the ray to see what it hits, but again let's just stick to lines for now. It's also possible to do a LineTraceForObjects, where we can check for Static or Dynamic Objects only but we're just going to use B圜hannel for now. This Line Trace is using the Visibility channel to see what objects to check against (basically can we see the object or not). LineTraceB圜hannel: This Node takes two World Space Positions and draws a line between them and checks to see what was hit. Which is why these nodes are called Transaction Nodes.So let's try not to get too complex too soon - here we're just making a tool that casts a ray down and then moves a Cube to the hit location, assuming it hits. Under the hood though everything undo-based is actually referred to as the Transaction System. This was a bit tricky to find since typing the word “Undo” in blueprint doesn’t give you much. Which then will allow you to finally undo properly you custom tool’s operation. End TransactionĬloses the gates and stops recording anything else to the undo stack. Then you can do whatever you want to the object and it will properly go back to whatever it was before doing anything to that object. Transact ObjectĮvery object you want to be undo-able has to be added by using the Transact Object node. Starts the undo stack and allows for anything after this call to be grouped into 1 undo operation. This was reported as a bug and marked “by design” simply because you can do it 100% controllable and custom in blueprints Begin Transaction This image shows an example of how to setup an undo-able function call in unreal 4’s blueprints.
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