Specs on glass???

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buzzkill
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Specs on glass???

Post by buzzkill » Tue Mar 01, 2011 8:14 am

I read something in regards to this topic a few weeks ago but I was wondering if some of you could help me understand better why these specs show up and what would be the remedy for it. It seems that I have only noticed them show up when I am rendering glass objects while utilizing the sun as the main light source. Mind you, this was my first attempt at creating a whole scene with flooring materials and light sources. What can I do to get rid of these "fireflies" if that's what they are called? Any ideas on settings would greatly be appreciated.

This was a model of a relay that I had some fun with. I let it render for 72 hours. Notice the specs. Also, the metal terminals have lost their shiny metallic look. Not sure why.
Image

Here is the same model but rendered using a quick studio. There are no specs here. I am wondering why only when I am using the sun as a light source these show up? Also, the terminals show up like they are supposed to (shiny metal)
Image

Thanks in advance for any tips and advice. It is greatly appreciated.

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Headroom
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Re: Specs on glass???

Post by Headroom » Tue Mar 01, 2011 8:57 am

Is there a liquid in that Glass, for example the "Clear Natural Water" from the DB ?
What rendering mode did you use ?
Exit portals ?

In general these artifacts tend to show up when small light sources are used in conjunction with glass and water. That's the reason that there are none of these "specs" in that flat lighted 2nd picture.

Increase the super sampling factor, change the rendering mode (perhaps one of the MLT modes in conjunction with water and glass) and let it cook longer even though 70h sounds rather long!

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buzzkill
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Re: Specs on glass???

Post by buzzkill » Tue Mar 01, 2011 9:05 am

Headroom wrote:Is there a liquid in that Glass, for example the "Clear Natural Water" from the DB ?
What rendering mode did you use ?
Exit portals ?

In general these artifacts tend to show up when small light sources are used in conjunction with glass and water. That's the reason that there are none of these "specs" in that flat lighted 2nd picture.

Increase the super sampling factor, change the rendering mode (perhaps one of the MLT modes in conjunction with water and glass) and let it cook longer even though 70h sounds rather long!
Originally I had water inside...but then removed it because it wasn't giving me the effect I was looking for. I am using Reinhard and Bi-directional PT.

What exactly are exit portals? All I know is that they are used in conjunction of where you want light to pass through. But where do you define these? Is that in Sketchup or in Indigo? I am using the thin glass material on the windows.

I will give those other suggestions a try. Can you help me understand exit portals a little better? I see people talking about them alot on here but not much detail as to what they do or how you set them. Thanks!

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Headroom
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Re: Specs on glass???

Post by Headroom » Tue Mar 01, 2011 10:33 am

They eliminate the need for Indigo to sample any objects behind them, thus speeding up rendering the "inside".
So cover all your windows and doors really any opening that light could enter from the outside with a simple plane with the surface normal pointing into the room. And then apply the Exit Portal material.

Also use a simple glass. No SSS and no cauchy_b (responsible for dispersive effects) as these converge rather slowly.

However, as they do eliminate sampling on objects outside, if you want to see objects outside e.g. trees you'll have to live either without exit portals and wait. Or you add them in postpro.

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buzzkill
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Re: Specs on glass???

Post by buzzkill » Wed Mar 02, 2011 3:23 am

Where is the exit portal material found?

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buzzkill
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Re: Specs on glass???

Post by buzzkill » Wed Mar 02, 2011 3:29 am

Here is the same model. 18 hrs. so far and looks much better. Using Bi-directional w/ MLT and sample size I think is 3. There is still some funky things going on in the tank. Due to lack of exit portals? (Still trying to figure out how to use them/where they are located). I'm going to let this one go for another day or so and see what happens. This one should be much easier to clean up in photo shop compared to the last one if need be.

Image

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Headroom
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Re: Specs on glass???

Post by Headroom » Wed Mar 02, 2011 5:09 am

In the Skindigo Material Editor there is a top row of 5 rounded buttons:

Import, Export UI, Search, Pick.

Click on UI. This allows you to define your own materials and you are not limited to the Presets.

For "Material Type" pick "Exit Portal" . Make sure the surface normal of the Exit Portal faces into the room.

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buzzkill
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Re: Specs on glass???

Post by buzzkill » Wed Mar 02, 2011 6:23 am

Headroom wrote:In the Skindigo Material Editor there is a top row of 5 rounded buttons:

Import, Export UI, Search, Pick.

Click on UI. This allows you to define your own materials and you are not limited to the Presets.

For "Material Type" pick "Exit Portal" . Make sure the surface normal of the Exit Portal faces into the room.
Awesome. Thanks!

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galinette
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Re: Specs on glass???

Post by galinette » Wed Mar 02, 2011 6:34 pm

buzzkill wrote:There is still some funky things going on in the tank.
I think these are real multiple reflections/refractions. The ones that were previously so slow that appeared as bright colored dots.

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http://www.eclat-digital.com

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buzzkill
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Re: Specs on glass???

Post by buzzkill » Sat Mar 05, 2011 12:45 pm

Exit portals mastered....well, almost that is.

Image

kdarius
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Re: Specs on glass???

Post by kdarius » Sun Mar 06, 2011 9:54 am

so in using exit portals you then photoshoped the sky and sun in?

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Pibuz
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Re: Specs on glass???

Post by Pibuz » Mon Mar 07, 2011 8:50 pm

When using exit portals the only rendered element left in the scene are just sun and sky :wink:

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buzzkill
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Re: Specs on glass???

Post by buzzkill » Tue Mar 08, 2011 8:56 am

kdarius wrote:so in using exit portals you then photoshoped the sky and sun in?
So not to confuse you, I rendered a whole new image after using exit portals on the windows and placing the sun position lower in the sky (which is why in the original images, you can't see the sun - it was higher up). The only thing that I did in photoshop in the final image was use content aware on a few minor pixels that didn't clear up after hours of rendering. They weren't bad, but it distracted the eye a bit from the image as a whole.

I also did another rendering using lens aperture tweaks which gave me some pretty cool beams of light emitting from the sun. Pretty fun :wink:

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