Rendertarget memoryleak / misuses?

Graphics
1

I am currently making a mapeditor for my game. The background is made up of 2 large Texture2D that I generate using a RenderTarget2D. This works very well when I only need to generate the textures once, however if this is done a lot (Which happens when mapediting) it starts using more and more memory. The memory is never freed again even though I am calling .Dispose(), I am at a bit of a loss. So it got me wondering if I am misusing the Rendertarget and if there is an alternative to what I am doing.

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Edit: I’ll add that not using .Dispose() increases the memory usage a lot

2

How are you certain the rendertarget part is taking up more memory? wouldn’t you expect a level to take up more and more memory as variation grows?

3

It only happens whenever the .DrawingToTexture() is called, regardless of whether a change has happened or not.

A gif showing the increased use of memory
The method call only happens once whenever the mouse enters a different tile, so it is not because it is running every update call.

Edit: I might not have ensured that it is only called once… Might be this, currently testing

Edit2: I wasn’t limiting it, limiting it decreased the time it takes, but still slowly creeping up.

4

I would say it comes from the fact that you create, each time you call DrawingToTexture():

  • a new RenderTarger
  • a new spritebatch
    And this is done twice when you call RefreshTexture().

You should create the RTs and the spritebatch when loading the app, this should resolve the problem, and as a bonus, should go faster.

I use 9 RTs in my engine and no problem with the memory allocation.

5

As a bonus, can you tell us why his approach causes a memory inflation…? I would have thought the spritebatch and rendertarget would just be destroyed when their containing method is done executing? i.o.words: What accounts for the ever increasing ram usage?

6

It’s the GarbageCollector which should free the objects, they are not freed as soon as you exit the method. (or you should use something like this:

using(SpriteBatch sb = new SpriteBatch(gfxdev))
{
…
}

to ensure it is.
As it is called when mouse hovering a different tile, and RTs are allocated twice each mouse move, maybe the creation is faster than the garbage collector can detect the generations that need to be freed.
As I have written, “I would say”, I’m not saying i’m an expert, but for sure creating variables each frames is really bad. Moreover when it comes to RenderTargets, which use a lot more memory than just an array depending on the resolution choosen.
A profiling of the app should point to the culprit.

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7

Thank you Alkher and monopalle, it was the Spritebatch, adding SpriteBatch.Dispose() to the end of the DrawingToTexture fixed it!
A single Spritebatch works as well.

I tried making a single RT, but the Texture2D is tied to the RT so that approach will only allow me to make a single texture, unless I copy it, which is very resource intensive.

8

Glad to help :slightly_smiling:

using(SpriteBatch sb = new SpriteBatch(gfxdev))
{
…
}

calls Dispose() implicitly :wink:

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