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Maarten Vis

Render artefacts on edges

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Hello friends,

 

I'm doing a render of my house and it's getting close to where I want it to be. But I keep running into artifacts on the edges. (see picture)

 

I use the physical renderer with global illumination, primary QMC and secondary Light Mapping. I use a camera with a f11 and 4 sec exposure.

 

Thanks in advance for the help!

 

Cheers,

 

Maarten

LBG_282_15c.jpg

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I think in many cases it´s caused by low samples value. Try to increase samples and with render region command try on critical place...

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This can also be GI-Bleed. Do the walls have volume or are they flat sheets? This tends to happen when walls are thinner than the samplesize, as the sample gets averaged with samples outside (which are very bright) and samples inside (which are very dark). When using any non-QMC-GI you should always work with volumes. It's not an issue with QMC as it works on a per pixel basis but it's best practice to always model with volume anyways.

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1 hour ago, DasFrodo said:

This can also be GI-Bleed. Do the walls have volume or are they flat sheets? This tends to happen when walls are thinner than the samplesize, as the sample gets averaged with samples outside (which are very bright) and samples inside (which are very dark). When using any non-QMC-GI you should always work with volumes. It's not an issue with QMC as it works on a per pixel basis but it's best practice to always model with volume anyways.

 

Very much appreciated to have a good technical explanation for why this happens. I learned something today ! 🙂 Thanks DF.

 

CBR

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7 minutes ago, Cerbera said:

 

Very much appreciated to have a good technical explanation for why this happens. I learned something today ! 🙂 Thanks DF.

 

CBR

 

Glad I could teach you something for a change 😆

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On 11/22/2019 at 3:31 PM, DasFrodo said:

This can also be GI-Bleed. Do the walls have volume or are they flat sheets? This tends to happen when walls are thinner than the samplesize, as the sample gets averaged with samples outside (which are very bright) and samples inside (which are very dark). When using any non-QMC-GI you should always work with volumes. It's not an issue with QMC as it works on a per pixel basis but it's best practice to always model with volume anyways.

 

Thanks for the help so far! I have extruded the walls and ceiling from splines. Could that be the issue? Would it be better to rebuild them using objects with volume?

 

And I don;t get why you say 'when using any non QMC-GI' because I am using QMC? Or am I missing something.

 

Cheers, Maarten

 

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3 hours ago, Maarten Vis said:

I have extruded the walls and ceiling from splines. Could that be the issue?

 

That may well be the issue if there any gap at all between these forms. Ideally they should all be one surface.

Although the issue with light leakage with flat planes applies to IC / LM only, it applies to everything if there are any gaps at all in your surfaces....

 

CBR

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On 11/23/2019 at 7:55 PM, Maarten Vis said:

 

Thanks for the help so far! I have extruded the walls and ceiling from splines. Could that be the issue? Would it be better to rebuild them using objects with volume?

 

And I don;t get why you say 'when using any non QMC-GI' because I am using QMC? Or am I missing something.

 

Cheers, Maarten

 

 

You said you are using QMC for primary and LM for secondary, so your setup is not all QMC 😉 that's where the leaks are coming from, I think.

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11 hours ago, DasFrodo said:

 

You said you are using QMC for primary and LM for secondary, so your setup is not all QMC 😉 that's where the leaks are coming from, I think.

You're absolutely right! When I switch to Irradiance cache for the second method the problem dissappears. Downside is that the rendering becomes extremely long. (14 hours and counting for a 800 x 530 image!) I'd love to know how to get those render times down!

 

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44 minutes ago, Maarten Vis said:

You're absolutely right! When I switch to Irradiance cache for the second method the problem dissappears. Downside is that the rendering becomes extremely long. (14 hours and counting for a 800 x 530 image!) I'd love to know how to get those render times down!

 

That's odd. Light leaks can happen with IC as secondary as well, as it's an interpolated technique as well. If you want to really have accurate lighting you need to go QMC + QMC or fix your walls, if you didn't do that already.


QMC + QMC is very slow but by far the best result as it's completely per pixel and no interpolation whatsoever. You can even disable Ambient Occlusion with this as the detail in the shadows comes from the QMC itself 🙂

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