Layers and Slowdown

Wasn't sure to post this in HWA forum or here, but since it isn't specifically an HWA question, I'll just post it here.

I'm about to implement parallax scrolling into my game via layers. However, I've heard that for some people, layers can cause a lot of slowdown. But I don't know how I could go about doing a good parallax effect without using layers.

So, is there really a slowdown problem with layers? Is it only in HWA builds? And if there is possible slowdowns, what can I do to avoid them?

Any input on this subject is greatly appreciated. Thanks.

In my experience, Layers will only cause noticable slowdown if three or more are used. I've been able to get away with four, or even five layers before. Whether you get slowdown may depend on how many objects are on the layers, how many fastloops you're using, etc.

I'd just experiment with it and see what you can do. :)

A while ago I was trying to layer multiple heights in my topdown prototype. So I had 4048*4048 frame size and 5 layers and a total of 5 layers. All had loops to paint the tiles all over and I changed layer when I entered buildings or moved on top of roofs and so on. It was not running very smooth at all.

Do not have anything considered a background above the bottom layer (there are many extensions considered backdrops). It will dramatically slow down your game if you do this, especially if you have scrolling.

I have up to 8 layers, they mostly have at least one background object. During runtime I'm turning them on/off, change transparencies and whatnot and I never saw any slowdown whatsoever.

My application is pretty small though, 320*256 with frames at 640*640 max (but usually much smaller), running at very low framerates so maybe the slowdown is here I just don't see it.

Also I was able to videocapture the game (which is additionally burdening the system - for example video capturing a simple game from RPG Maker grinds the framerate to single digits) without any slowdown... so I guess if you stay small you'll be fine.

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Originally Posted by Pkeod

Do not have anything considered a background above the bottom layer (there are many extensions considered backdrops). It will dramatically slow down your game if you do this, especially if you have scrolling.

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So, if I want parallax scrolling, I'd have to use backdrops on the bottom layer, and then the "background" in the upper layers would all be actives? That probably won't work with my game, unless I create a tiling system instead of just making the level in a frame. Assuming I'm understanding all of this correctly. Because I'm making a platformer, so if I don't use backdrops for the ground the player is on, I'd have to use actives (since I want a background behind the layer the player is on) Or is there some other way?

As Docilemouse said though, I should just experiment and see what happens. But I'm not sure if it will cause slowdown for everybody or just on certain computers, so I don't know if I can accurately guage this.

Layers in themselves don't cause slowdown - I have an options frame with about twelve or so, as they're a useful way to separate out multiple dialogue boxes.

But their use combined with scrolling can cause a lot of slowdown because of the way that the collision masks work in MMF - the first layer has a complete collision mask calculated before the frame starts, and the ones above it are tested object-by-object. This means that if the majority of your gameplay happens on a layer higher than 1, it'll tend to be slower - often unnoticeably but sometimes a lot slower, if there are a lot of things going on.

So on my larger frames I've reverted to using background system boxes for parallax scrolling (I think Background Images can do this as well, now), which allows me to take the gameplay down to layer 1 again.

By the way if anyone doesn't know how to use the Background System Box for parallaxing, I wrote an article a few years ago (sadly the link supplied within the article is dead but its pretty straightforward)

http://www.create-games.com/article.asp?id=1255

I also have an example using the Background System Box for parallaxing scrolling on my website. There is also an example using multiple layers.

Marv

Okay thanks guys. I will definitely check out those tutorials using the background system box.

I do have a question about using the background system box however. If I have a large level, how is that going to work if I have a huge image? Wouldn't that cause a performance hit?

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Originally Posted by DavidN

Layers in themselves don't cause slowdown - I have an options frame with about twelve or so, as they're a useful way to separate out multiple dialogue boxes.

But their use combined with scrolling can cause a lot of slowdown because of the way that the collision masks work in MMF - the first layer has a complete collision mask calculated before the frame starts, and the ones above it are tested object-by-object. This means that if the majority of your gameplay happens on a layer higher than 1, it'll tend to be slower - often unnoticeably but sometimes a lot slower, if there are a lot of things going on.

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Would be nice if we could specify which layer is the main game layer to calculate the collision mask. That way you could have layer 1 be the background scrolling and layer 2 the main game layer. That would solve the issue of layers and slowdown I would think. And would make for really easy parallax without cause for worry.

I guess the best thing to do is to put all the collisions, detectors etc on layer one and have all the actual graphics on layer 2 or above.

At least that's how I have it set up - with the addition of other layers: layer 2 for far background (sky, mountains), layer 3 for the player, NPC layer and all the worldly graphic, next layer is for the masks etc and another layer for the interface.