Smooth isnt smooth when I render in cycles

Im using blender 2.71. Im not sure whether Im doing something wrong here or if there’s a glitch with 2.71 which is maybe known and resolved with 2.72 ?
Anyway -
I was seting up nodes groups to render a planet based loosely on a video tutorial I saw recently.
the land distribution etc works great and Im getting the hang of bumps, normal maps and cycles displacement etc.

But look at the sea on the shadow side. You can see the quads in the mesh. But, Ive smoothed the object ( its a subdivided cube) , and autosmooth is set on ( its the same if autosmooth is off).

Given that I have no bump mapping, normal mapping or displacement effecting the sea then it cant I think be due to those things. Why would i not get a smoothed surface in the sea given that Ive masked that area from any other influence and that my object is set smooth and has autosmooth on?
Any ideas or suggestions please?


Are you going to upload the scene file somewhere (e. g. to pasteall) so we can take a look? Or is this supposed to be a guessing game?

Ok I tried adding a simple sky texture to the world but the problem persists. Quads from teh mesh still showing. I put multiimportance sampling on for the sun and tried changing the sun side. Making the sun size very large makes it go away - but only because theres nbo shadow transition then. Ill create a small blend and try to upload it.

Yea, but that object in my render is already sporting a level 5 subdivision. Surely cycles shoudl be rendering it smoother than that and not showing quad artifacts at the shadow boundary with that level of smoothed subdivision?

Doesn’t look like the typical terminator artefact to me (that’s what the effect the two links in this thread refer to is called - quite common in many render engines, btw)… File?

What I’m asking myself is: Why use displacement on this object at all? If you look at the outline of that globe, you see no deformation/distortion from displacement whatsoever, it is still a perfect sphere. If you wanted something like this…


…(mind the “real” elevation of the continents visible at the outline) I could understand the displacement, but wouldn’t bump/normal mapping alone have been perfectly sufficient for your desired look with much, much less geometry? Subsurf level 5(!!!) - what for, if you can’t even see the effect?

Idk then. Probably displacement is able to mess this up even if you isolate it. Using vertex groups?

Ikarishinji - your right that its showing no displacement. I had it turned right down or off when I rendered the image. The reason for displacement was two fold. First I wanted alook similar to the one you just posted. And second and probably more important im only just trying cycles displacement feature. I was tryiing to comobne this in a node setup with bump mapping and normal mapping. However Im increasingly convinced from looking at the renders of simple spheres in the other threads that the problem is not due to any of my bump mapping.

Eppo - Im sure there will be some way to do it. I’m finsihsing up this evening here but Ill post a blend tomorrow evening and see if this reporduces just with a simple subdivided sphere.

Here you have it - two identical cubes - one with procedural displacement, another - normalmap.


Eppo - In the displacement one (on the left) you dont have any artifacts on the smooth surface part of the sphere. Can you tell me what level of subsurface you have on that sphere and what you lit it with?

@Eppo
And see how that looks quite different than in the OP’s screenshot? The terminator artefact causes a harsh border between polygons (one already dark, the next still bright) and not the kind of gradual degression seen in Bunc’s globes. There’s more to it.

@Bunc
Just to be sure: With “Cycles Displacement” you don’t mean just plugging a texture here, right?


Because that’s plain old bump mapping.

You mean “true displacement”, which is about as experimental as you can get with Blender?


Or do you mean using a displacement modifier?

Im a learner IkariShinji but I try to do things right if I can figure it out ! No, I didnt just plug a texture into the displacement slot and expect displacement. I turned on teh experimental setting and selected. Bump, then tried True then both amd also tried the dicing. I havent chcked yet to see if im getting teh same artifact with each of these settings. Ill do that tomorrow and report back. Whether its the terminator or not its annoying and I want to figure out whats causing it and how it can be avoided / resolved.

Hey, no offense meant.
Blender calling that node input “Displacement” and then having it default to bump mapping is misleading as hell and you would be surprised how many users get fooled by this.

Nonetheless are you using a highly experimental feature and unexpected results are, well, to be expected. The Displacement modifier is - as disappointing as that might be - still the only reliable displacement option in Blender.

Sorry i was off the grid early yesterday - i’ll attach file later. Cube had lv2 ss applied initially, then it was ss2 and right after ss3; then displacement map. Lights - pink sharp Sun from above and likely bluish area from bottom/side.

It is Displacement = Bump when Experimental render mode is switched OFF. If it is ON then it happens to be real Displacement of some sort, shaky, prone to crash often and one needs constantly click checkbox to get it properly updated (forgot which one - somewhere near :)). So you could use that if you like gambling ;). Sometimes it can look surprisingly good.

I see, there are differences in how artifacts look - could be that light sharpness and maybe normalmap resolution/strength can have some influence on it.

OPs file would shed more light on this.

http://www.pasteall.org/blend/32286

Don’t use the displacement slot at all. It’s unfinished and broken. If you need displacement, use the modifier. What you’re getting is called a terminator error, and is an unavoidable result of path tracing. You’ll need to increase the resolution of your object (make sure you have both viewport AND render subdivision turned up).

I’ve noticed this problem too when using normal maps on spheres and it bugs the crap outta me when people say ‘just add more geometry’. No. Stop it. If I wanted gazillions of faces I’d use actual displacement instead of a freaking normal map, mmkay? I really don’t get why some people refuse to recognize an actual problem when it’s there.

Well, since the OP never provided the scene file he promised, we actually have no idea what the “problem” actually was.

Other than that: Terminator artefacting is something the majority of unbiased renderers suffers from and the only suitable workaround for that in Cycles so far is increasing the subdivision. What else could/should we have answered to the OP? “Go rewrite the Cycles code” or “live with it and write a bug report”? I fail to see how that would have been helpful.

You’re barking the wrong tree here. This is something you have to solve by discussing it with the devs and not by shouting at the forum users trying to help and to offer a solution.

@IkariShinji - Not sure how you decided I was shouting since I never used any exclamation points or caps, but that’s entirely beside the point.
Anyway, I did submit a bug report for this and got at least one response telling me to increase the face count, saying much like you did that cycles apparently can’t handle smooth shading by nature. On which statement I’m calling baloney.

2 subdivisons without smooth shading:
[ATTACH=CONFIG]342207[/ATTACH]

2 subdivisions with smooth shading:
[ATTACH=CONFIG]342208[/ATTACH]

The problem (in my experience) ONLY arises after I add a normal map and use the normal map node, set to tangent, and plugged into the shader normal. Instantly, the faces are again made visible, completely counteracting the smooth shading (see image on left). Sometimes this effect is oddly more visible in some areas than others, as seen here with the opposite side of the sphere. This scene uses a sun lamp, btw…just in case that’s important somehow.


Additionally, the effect seems to be lessened (or even removed entirely) by setting the normal map node to object space, as seen on the right side of the image.

All that to say, this clearly isn’t a ‘not enough geometry’ problem…2 levels of subsurf combined with smooth shading is generally enough to get a smooth result. It’s just that there’s clearly an issue (or dare I say…bug) when normal maps are used, that can only really be addressed by the developers. Hopefully somebody was listening when I submitted my bug report.
So. The next dang time somebody says to add more geometry to fix this problem, I’m going to glare very sternly at them through my computer screen.

OK, I’m all for lively discussion!
Since I’m usually not a normal map kind of guy, I did a little testing for myself to have a factual foundation. My experimental setup is a UV sphere (60 segments and rings - yeah, quite dense already) with a single sun lamp (2.5 cm, MIS) and a dark grey environment.

I will render that sphere 4 times: with and without subsurf level 2 / with and without a normal map (UV mapped, tangent space, default settings, the normal map image texture is a 24-bit PNG):


My conclusions:
a)
The normal map seems to increase the terminator issue with and without subsurf, albeit to a lesser extent on the subsurfed sphere.

b)
Increasing the density of the geometry by adding a subsurf modifier greatly reduces the artefacting on the spheres with and without a normal map. The very slight artefacting on the subsurfed/normal mapped sphere vanished at a subsurf level of 3.

c)
“My” normal map seems to produce lesser artefacting than “yours”. In your bug report sergey already suspected that the quality of the normal map might be part of the problem. As already said, mine is a 24-bit PNG in 4096x2048 pixels.

From all that I see no reason not to recommend subsurf as a means to lessen artefact issues (glare sternly all you want…;)). I will gladly admit that normal maps apparently contribute to the problem, but the level of contribution seems to be dependent on other factors, like e. g. the normal map quality.

I understand that it is unfortunate having to crank the subsurf up just to avoid artefacts with normal maps. But then again Cycles is a very young render engine and is not entirely production ready in many ways. One day Cycles will get there…:yes:

Well, i figure one is able to screw bumpiness in a different ways but in general things just work.
Of course you can’t expect making some kind of Big Small planet using normalmap applied to the default Sphere; any reasonable surface ‘change’ is possible and it is even possible to combine normalmap’s and Cycles output node’s Displacement (however buggy it might be) input effects. Here’s the result - 1.4k jpg image you can Google for, all hated Gimp to get normalmap out of it (same degree jpg quality btw), default Sphere with lvl 2 subsurf. There are limits - not these, turn Displacement or normalmap up and you’ll get mr. Terminator appear. Until you keep in limits he’s not coming.
http://www.pasteall.org/pic/79266

While it’s true that I never thought about the resolution of the normal map being part of the problem, that still doesn’t explain why the problem seems to be fixed when I change the normal map mode to ‘object’ instead of ‘tangent’. Clearly, the normal map is good enough for that, so why won’t it work if I want to use the UVs? That’s my question.