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EricWMLim

Glass material showing white speckles in ray trace

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Hi,

 

Can anyone please help me here?

 

I have been reading the forum on ray trace topics especially on glass materials and there are a few articles on recommended settings for glass materials in ray trace.

I have also watched the ray trace training videos too.

 

There have been suggestions in the past forum to overcome glass materials issues for ray trace.  Generally they are:

1) change the glass to General Material and increase transparency to 50-70% and increase emissivity a bit

2) use the Crown Glass with refraction index 1.52 and select "compute caustics" and "use photon mapping"

3) use transparent material for glass material and tweak the refraction index

 

I have tried all the above three methods and spent countless hours but I still ended up white speckles.  Worse still, the light bulb in the glass pendant lights looked distorted due to the refraction index of crown glass.  

 

In the attached ray trace image, I have placed 3 pendant lights. 

For this ray trace image, I opted to use Crown Glass with refraction index 1.52 and select "compute caustics" and "use photon mapping"

 

The furthest globe pendant light is turned OFF, with the middle one turned ON, and the one closest to the camera is ON.

All pendants have speckles and this image was run for 10 passes.  The light bulb in the glass ball pendant lights are distorted in the first and third.

 

How do I ensure the light bulb inside the glass ball pendant light is not distorted AND getting rid of the white speckles?

 

I don't believe running more than 10 passes, say 100 passes will eliminate the white speckles.

 

Anyone has any ideas?  This is frustrating for me because it means I have to refrain using glass materials for ray trace and this is just not possible especially when doing bathroom designs with glass shower screens.

 

Thanks,

Eric

 

 

 

 

Kitchen_with_glass_pendant.zip

Glass with speckles.jpg

RT 1.PNG

RT 2.PNG

RT 3.PNG

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This is a common issue and I'm not sure there is a 100% solution. More passes will reduce this and will eventually eliminate them, but it may take 100 or more to do the trick. I have found that this occurs with all transparent materials including glass, though the degree may vary according to the material/glass property settings. It seems to be related to situations where light has to pass through two or more layers of glass and more specifically light being reflected from surfaces behind the glass. If you turn off photon mapping I think you will find that the speckles will disappear, but you will loose the effect of photon mapping and this may not be desirable. It's hard to say but I believe the main source of the reflected light is from the recessed light fixtures near the wall with the opening to the living/family room. Try turning those off and run a trace to see if that has an effect.

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On 9/5/2017 at 5:15 AM, EricWMLim said:

 

If you turn off Compute Caustics does that problem still exist? ..and what new problems occur..

You can google caustics or do a search as we all have gone over its intended use and drawbacks. Laymen terms it makes the trace engine compute light refraction through transparent materials...1 light in a glass globe adds an untold and large number of light particle traces

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Hi Graham and Rene

 

Thanks for your inputs. 

 

I tried running for over 100 passes and the speckles cleared up a bit more but they were still there.

The settings were used with "Compute Caustics" and "Photon Mapping"

 

Removing the recessed lights in the living room made no difference in the reduction of speckles.

Unchecking "Compute Caustics" didn't reduce the white speckles either.

 

Thanks,
Eric

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7 hours ago, EricWMLim said:

Hi Graham and Rene

 

Thanks for your inputs. 

 

I tried running for over 100 passes and the speckles cleared up a bit more but they were still there.

The settings were used with "Compute Caustics" and "Photon Mapping"

 

Removing the recessed lights in the living room made no difference in the reduction of speckles.

Unchecking "Compute Caustics" didn't reduce the white speckles either.

 

Thanks,
Eric

 Eric, I was referring to the recessed lights in the kitchen along that wall. Some users have had some success by adjusting the ambient occlusion, try upping the max to see if that helps out. This will of coarse will change the overall scene so you might have to adjust the image properties a bit.

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Thanks Graham.  I misunderstood your original message on the lights.

 

Ok. I will change and see how the scene looks like.

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