Why isn't parallax mapping used more?

Unknow0059

I'm a layman. I signed in specifically to ask this.
It seems like a really cool technique that I don't ever see in games, except for the ones mentioned in the wiki article, of course. Oh, Spider-Man PS4 gives a similar result, but I found out it does not actually use parallax mapping.
Why hasn't it replaced normal maps entirely? Is it especially expensive when compared to a common normal map?

Eric Chadwick

It's probably used more often than you're aware, just with more subtlety so it's more difficult to discern.

Parallax mapping is fairly expensive to render, at least for the methods that work well, and shader complexity is probably the most common cause for rendering slowdowns in current tech. So it's often avoided.

It's also fairly limiting because the parallax effect causes it to look like it's "below" the surface it's applied to. Which makes it difficult along boundaries. Normal maps on the other hand look like they're at the same level.

But hey, it's another trick in the arsenal. Good to have in specific cases.

Oh, and welcome to Polycount! Great first question.

guitarguy00

Eric Chadwick said:

It's probably used more often than you're aware, just with more subtlety so it's more difficult to discern.

Parallax mapping is fairly expensive to render, at least for the methods that work well, and shader complexity is probably the most common cause for rendering slowdowns in current tech. So it's often avoided.

It's also fairly limiting because the parallax effect causes it to look like it's "below" the surface it's applied to. Which makes it difficult along boundaries. Normal maps on the other hand look like they're at the same level.

But hey, it's another trick in the arsenal. Good to have in specific cases.

Oh, and welcome to Polycount! Great first question.

Is Parallax Mapping essentially the same as a Displacement map?

Kanni3d

@guitarguy00
It's like displacement, but without the tessellation if that makes sense. It's still the same amount of geometry, but loads more shader instructions/trickery.

https://www.artstation.com/artwork/XBnL3l

guitarguy00

Kanni3d said:

@guitarguy00
It's like displacement, but without the tessellation if that makes sense. It's still the same amount of geometry, but loads more shader instructions/trickery.

https://www.artstation.com/artwork/XBnL3l

Ahh yes I see. Have seen it briefly used in Unreal but was abbreviated to POM. It still confuses the hell out of me lol. 

Kanni3d

Not to be confused with PDO either (Pixel Depth Offset)

Obscura

Its not like displacement... Parallax is a visual trick that does not modify the geometry, and therefore the silhouette neither. Know those "3d stickers" in real life? Its kinda like those. Displacement modifies the position of vertices. If tessellation is enabled too, it creates new vertices on the fly and offsets those newly created verts too. Performance wise, parallax and displacement with tessellation is actually similar on modern hardware. If they are overused, and badly used, both of these techniques can result in bad performance quickly.

guitarguy00

Obscura said:

Its not like displacement... Parallax is a visual trick that does not modify the geometry, and therefore the silhouette neither. Know those "3d stickers" in real life? Its kinda like those. Displacement modifies the position of vertices. If tessellation is enabled too, it creates new vertices on the fly and offsets those newly created verts too. Performance wise, parallax and displacement with tessellation is actually similar on modern hardware. If they are overused, and badly used, both of these techniques can result in bad performance quickly.

Very interesting. I'm thinking the illusion is broken when looked at from sharp angles much like Normal Maps?

Obscura

Its broken when you see the silhouette. 


Pixel depth offset can help this, but only if there is another mesh intersecting. So in this particular case, it wouldn't do anything.

guitarguy00

Obscura said:

Its broken when you see the silhouette. 


Pixel depth offset can help this, but only if there is another mesh intersecting. So in this particular case, it wouldn't do anything.

Ahhh yes this makes sense to me now.

Unknow0059

I see. So it's more expensive and the edges look strange. I thought there'd be some fix for the latter but I gues not. Thanks for the replies.

poopipe

There is a fix for the latter, it's just even more expensive