Does making a new Vector3() have an impact on performance?

Question

There are time where I need to modify a vector, like "GameObject.Transform.position". For something that runs each frame, does it make a difference if I make a new vector each time, like this: "GameObject.Transform.position = new Vector3(1, 1, modifiedValue);"

or i avoid making a new vector each time, by doing this before the update frame: "Vector3 v = new Vector3();"

then this in the update:

"v = GameObject.Transform.position; v.z = modifiedValue; GameObject.Transform.position = v;

Answer 1

Answer by maormenashe · Feb 10, 2020 at 11:10 AM

I guess when you say "by doing this before the update frame" you mean having it as a member of the class.

Since Vector3 is a struct it will go on the stack depends on the scope you're using it, if you use it as a member of a class which is a reference type then you'd have it saved on the heap, if you're initializing a new instance in a method scope then it will recreate it each time on the stack.

So considering that, and your specific case, yes, it would be better performance wise to use it as a member. In your specific case you'd barley be able to see any difference since the performance impact is very small!

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Answer 2

Answer by Aka_ToolBuddy · Jun 09, 2020 at 07:49 PM

Yes, it makes a difference. If you want a more detailed answer, with comparison of IL instructions, take a look at this thread: https://forum.unity.com/threads/vector3-and-other-structs-optimization-of-operators.477338/

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Answer 3

Answer by Klarax · Feb 10, 2020 at 09:39 AM

probably not to the point where its an issue (depending on your game of course)

why cant you define it at the top of script and use it when needed?

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Magso · Feb 10, 2020 at 10:31 AM -1

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C# requires a new Vector3 because it can't modify the transform's property values directly. It would be easier in this case to use Translate

Bonfire-Boy Magso · Feb 10, 2020 at 03:36 PM 0

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That requires you to have another Vector, but it doesn't mean you need to create it afresh on every frame. v.x=x; v.y=y; v.z=z; doesn't create a new Vector so something like the OP's own suggested alternative would avoid it too.

Bonfire-Boy · Feb 10, 2020 at 03:38 PM 0

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@$$anonymous$$larax that's exactly the solution they're proposing - the question was whether or not it makes any difference.

Does making a new Vector3() have an impact on performance?

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