Render artifacts

I’m encountering a persistent render artifact problem. For a description, pictures and how to reproduce it, please visit:

http://mumm.uuuq.com/blender/blenderproblem1.html

Please post replies in this thread.

Thanks.

Don’t get me wrong here, but the problem is not the renderer but you being lazy when it comes to modelling…:wink:

These artifacts occur on surfaces, if two meshes intersect and the corresponding faces occupy exactly the same position in space.

This problem is comparatively easy to avoid: You could …
a) use only spotlamps with buffered shadows (No raytracing for shadows) or
b) (To be preferred!) Just model things like you would construct them in reality, which means that solid pieces of matter normally do not intersect.

Thanks for your input, Ikari. I take that as constructive criticism. :yes:

I already tried the spotlight/buffer method, and it can work if I spend some time on it. But it is limiting me too much. (Or laziness struck again.)

Lazy … oh yes! I blame that due to being born on a Friday. But that notwithstanding, I needed to model the house quickly, so I took the most direct method. It allowed me to make structural changes quickly as the house grew. Each beam has a bevel – I would have wasted too much time to fix them if I had to take the non-lazy route. And I did not know about the artifacts problem (or forgot about it since I blend only occasionally) until it was waaay too late.

I was hoping that there is a quick fix, hence my post. But judging by the time it took me to research this, I could probably have remodeled the whole house using the non-lazy route by now.

So on to my other ramblings: does Yafaray also cause these artifacts?

Or is it something that the Blender developers can fix in future releases? Do other 3D programs encounter the same issue?

IkariShinji is correct.

Don’t model with completely co-planar faces. I suppose it’s faster and more configurable, but…

Why not just stop that vertical beam at the bottom of the horizontal one instead of protruding into it?

I just did a quick test with YafaRay and it did not show these artifacts. But there’s no guarantee that it will work with all lighting methods and under all circumstances.

From your question I guess that you have no experience with YafaRay so far?
Then be warned: Learning to make full use of a new render engine might take longer than reworking the geometry of your house model…:eyebrowlift2:

Quick fix = grab the horizontal beams and move them 0.01 blender units x and y and z.

But beware when the overlap is small and camera clip distance is small and the object is far away then the camera “sees through” and tries to render the meshes in the same place anyway - so if that happens turn clipstart up.

Yep, it is a Blender render bug. Lux does not exhibit this render problem either. But it will never be fixed, so get used to it, get over it or use another render system.

Modeling purists please avert your eyes! You have been warned!

Another ‘quick fix’ that you might try is to use a Boolean Union on the beams.

Important: Make a backup copy first. I also suggest you try it out on a simple model to see how it works. (The default for the operation leaves behind the original objects for you to discard.)

This should take care of the overlapping faces but will introduce many additional vertices in the model that may or may not cause other problems down the road.

At least, this worked for me using the simple example you gave in the original post.

Thank you guys (and gals?) for the advice. I’ve learned that there are indeed many ways to kill this cat. I’ll keep it in mind for future projects and try a different renderer this time round.

I’ve used Yafray a long time ago, but switched to the internal blender renderer because it seemed faster and most tutorials were based on the internal renderer anyway. But it was long ago, and I can’t remember whether it solved the artifacts issue. Thanks Ikari for checking. It sounds encouraging.

Atom, thanks for the Lux tip. I’ll try a slice of that too. (http://www.luxrender.net)

A “quick” 30 minute render with Lux resulted in this:

http://mumm.uuuq.com/blender/blenderproblem1h.jpg

In comparison, the blender render took about 59 seconds. I hope that some of the settings in Lux can be toned down to speed up the render.

But it looks encouraging. The artifacts are gone.

Interesting, I notice that the light bulbs are visible in a Lux render…

And the winner is … Yafaray!

http://mumm.uuuq.com/blender/blenderproblem1k.jpg

Gone are the artifacts.

I see some jaggies though. Hopefully there is a way to fix it by playing with the settings. But it is usable enough for my purposes as is.

Yafaray rendered this scene in 11 seconds. Compare that with 59 seconds using the default blender renderer … or forever using Lux.

The jaggies will go away with decent AA settings.
Try these for a start, which will imho give a reasonable balance between quality and rendertimes:

‘Settings’ tab -->

AA passes: 2 | AA Pixelwidth: 1.800
AA samples: 4 | AA inc. samples: 6
filter type: mitchell | AA Threshold: 0.0200

Thank you Ikari. I used your recommendation, and here is the result:

http://mumm.uuuq.com/blender/blenderproblem1l.jpg

Render time: 66 seconds.

Looks great! Thanks!

Yep,could you ulpoad a little bigger version of it?As about artifacts,there might be a lot of reasons,insufficient sampling caused by either small sampling rate itself of big color contrast,also the whole bunch of problems caused by FG,GI.Itd be faster if you just upload a scene in .ma
runtime interopservices externalexception a generic error