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Artifacts in large models
Posted: Tue Mar 15, 2011 10:56 pm
by stefan_kaplan
This might not be a plugin-related problem, but I keep getting ugly artifacts when rendering large SketchUp-models.
I simply cant find out what causes the problem, but when parts of the geometry is moved around, the artifacts tend to move around as well.
Direction of normals doesn't seem to be the answer...
I have to deliver a render of this model in quite high resolution in a few days, so please tell me if you have seen this before, and what might be done
All the best.
/Stefan
Re: Artifacts in large models
Posted: Tue Mar 15, 2011 11:11 pm
by JDHill
Thanks for uploading, I will take a look. I haven't noticed anything like this before -- is it possibly related to overall scale, or to the use (or non-use) of instances?
Re: Artifacts in large models
Posted: Tue Mar 15, 2011 11:17 pm
by stefan_kaplan
Originally it's not my model, but I've observed that every building is defined as a component.
I'll try and render with "instances" turned off.
By the way - the artifacts appear on both OSX and Windows...
Re: Artifacts in large models
Posted: Tue Mar 15, 2011 11:22 pm
by stefan_kaplan
Turning off instances doesn't seem to make a difference.
I'm not sure what you mean with "overall scale" though...
Re: Artifacts in large models
Posted: Wed Mar 16, 2011 12:04 am
by polynurb
i have seen something like this..
it happend when i had a very large lens length (trying to simulate ortho view), try the same view with smaller lens like 50mm.
daniel
Re: Artifacts in large models
Posted: Wed Mar 16, 2011 12:22 am
by JDHill
I can reproduce the artifacts here, and I have managed to reduce the model to two components (Freifläche_1644 & Freifläche_1745) without losing them. As you found, I saw no difference with instances on or off, and I have also tested against different materials and with simplifying the scene parameters as much as possible.
The only factor I am able to find which affects the artifacts is the camera's distance from the scene; past a certain distance, artifacts begin to appear, while closer in, they don't. That's what I meant by asking about the overall scale of the scene; whether it was millimeters or kilometers. I will have to send the MXS to core developers to find out for sure, but my instinct is that the two components have coplanar surfaces (I say that because individually, neither one has artifacts), and that with the camera as far from the subject as it is, you are running into numerical precision limits of the machine.
Re: Artifacts in large models
Posted: Wed Mar 16, 2011 12:23 am
by stefan_kaplan
Thank you, Daniel.
You are completely right!
The artifacts disappear when changing the field of view to a wider angle.
I think it's really important though, to be able to render at 1deg.
Actually I'd rather render at 0.001deg., since 0 deg. is not possible (right?)
/Stefan
Re: Artifacts in large models
Posted: Wed Mar 16, 2011 12:28 am
by stefan_kaplan
JDHill wrote:...you are running into numerical precision limits of the machine.
That would be my guess as well.
When the Field of View is down at 1deg., the distance between the camera and this big city model must be very large - and some sort of limit in precision occurs...
Re: Artifacts in large models
Posted: Wed Mar 16, 2011 12:54 am
by polynurb
stefan_kaplan wrote:
I think it's really important though, to be able to render at 1deg.
Actually I'd rather render at 0.001deg., since 0 deg. is not possible (right?)
/Stefan
glad it helped!
i actually had the problem in rhino, same thing though;
i forgot about the problem until i read your post title. i'd also like to see higher lenses work, or if it is also dependent on model size, some indicator that tells when the scene is out of "limits" for a given lens.
daniel