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Bump mapping

Beta84
Honored Guest
I heared in a video from Michael Abrash that Bump mapping dosen't work anymore for VR. Is that right? (Can't tested by myself don't have DK1, I'm waiting for my DK2)
19 REPLIES 19

geekmaster
Protege
"tomf" wrote:
All of rendering is a hack. But normal maps work significantly worse in VR than on a monitor because the combination of stereo and fine positional motion mean it is very obvious when something is a flat plane with "odd" lighting, and not actual geometry. ... One hack for these is to not use the vector to each actual eye in he lighting equations, but to instead use the vector to the "middle eye" for rendering both views. This at least avoids glaring stereo disparity, even if it doesn't look "correct". It doesn't solve the problem entirely though.

This is a tricky subject, and no doubt we'll discover other accepted techniques that don't work that well in VR.

No doubt ray tracing will replace all these perceptual hacks some day. Until then it is a delicate balance requiring subjective decisions best made by the end user. We each have different tastes, and even differences in how we perceive depth. The problem with normal mapping may bother me more in 3D movies because I like to sit front center, for full FoV, where my increased stereoacuity lets me see such defects much more than those sitting farther back in the movie theater. VR is much like sitting in the front row...

I was mostly arguing the case for bump mapping as a viable option because of this thread making claims in near absolutes. There may be times when the hardware cannot supply the desired level of detail and bump mapping may come to the rescue to supply extra subtle detail. And it must be kept subtle to stay below the conscious perceptual annoyance level. It really depends on whether the game play or the eye candy is the most important element of the game, and which details are meant to draw the player's attention. Slight of hand and perceptual leading and pacing go a long way in making the player feel the extra details without looking too closely at them. When we have ray tracing engines, I am sure we will discover new perceptual "uncanny valley" effects to deal with.

raidho36
Explorer
Let's say bump-mapping is a viable solution if you don't expect any stereoscopy whatsoever on the triangle in question. That is if it's very far away that there's no stereoscopic divergence, or the texture almost completely flat and bump-mapped light deviations are too slight to be picked as a relief where lack of expected stereoscopic cues would yield perception mismatch. Otherwise you would see a striking fakeness of bump-mapped lighting effect, in this case you should use either actual mesh or parallax map (those are work a charm in VR).

MrMonkeybat
Explorer
So does VR makes micro polygon tessellation or parallax occlusion mapping a must have then.

geekmaster
Protege
It is all about stereoacuity. I will concede that it is easier to ban a tool outright, than to enforce appropriate usage when that usage depends on the subjective bounds of perception. Some of us like to explore such bounds, which is why absolute rules and proclamations annoy us.

Using such a tool wisely can be difficult. A case in point was the movie "Monster House 3D" (mentioned above) which looked pretty bad in 3D when sitting near the front row (some 3D objects looked painted onto flat surfaces), but probably looked fine to the majority of the audience sitting behind me. At least in VR, such problems will be mostly dependent on HMD display resolution rather than viewing distance, and software can adapt to the known resolutions of supported models.

Or more expeditiously (from a political perspective), just ban all tools and methods that might be misused. 😮

EDIT: The alleged "Bump mapping doesn't work anymore for VR" quote was obviously a simplified generalization, rather than an absolute truth.

cybereality
Grand Champion
I don't think anyone was saying you absolutely can't use normal mapping for VR. Of course developers will want to use the available tools, and a game may already be heavily reliant on these features if being ported from 2D. The point was just that the effect is more apparently "fake" in stereo 3D and not as effective as on a monitor. As I mentioned, there are other more modern techniques that will look good (i.e. tessellation and displacement maps).
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geekmaster
Protege
"cybereality" wrote:
I don't think anyone was saying you absolutely can't use normal mapping for VR. Of course developers will want to use the available tools, and a game may already be heavily reliant on these features if being ported from 2D. The point was just that the effect is more apparently "fake" in stereo 3D and not as effective as on a monitor. As I mentioned, there are other more modern techniques that will look good (i.e. tessellation and displacement maps).

As you can see in the link I gave above to Fabien Sanglaard's site, bump mapping is often combined with parallax mapping (using a heightmap texture) to avoid this problem, perhaps more effectively than displacement mapping alone, and certainly side-stepping this whole stereoacuity issue that makes simplified poly meshes look flat in VR when viewed too closely or at too large a scale factor.

Perhaps you guys are talking about 2D bump mapping without clearly stating that you are applying such a constraint to this problem domain. If so, why would you do that? That just makes things confusing and illogical.

A quick google search found this bump map filter with parallax displacement for 3D use:
"

MrMonkeybat
Explorer
Sound like you are not disagreeing with them just with there definition. Most of the time when people refer to bump mapping it does not have displacement when they have displacement or parallax the refer to it as displacement or parallax mapping.

For over a decade now allot of game engines have saved performance by doing bump map shading without paralax When something like Unreal engine has parallax they tout that.

The wikepedia article on bump mapping defines it as ontly affecting the shading not displacement and use this image to show the diference.

http://en.wikipedia.org/wiki/Bump_mapping

Beta84
Honored Guest
So I could use parallax mapping or should I use displacement mapping / PN triangles tessellation?

geekmaster
Protege
"Beta84" wrote:
So I could use parallax mapping or should I use displacement mapping / PN triangles tessellation?

I prefer 3D displacement mapping (which I learned as "bump mapping" back in the day, why there were terminology disagreements earlier in this thread). I see Googly sources show the meaning as visualized in the orange spheres in a recent post above. So, technically speaking in modern terms, it seems that traingle displacement mapping is not really considered as "bump mapping" these days. Before the internet, companies tended to develop their own custom technical terminology. Widepread distribution of terminology definitions via the Internet is helping standards form with more recognition.

djsainthubert
Explorer
https://www.youtube.com/watch?v=cAnw1sXRd_8 please someone convert Perfect Dark Zero to VR for the lols... the bump mapping in the game is hilarious