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Shane Deters avatar image
Shane Deters asked ·

HDRI FOR IBL CLIPPED OR UNCLIPPED

I have a HDR file that is unclipped, when I use this as the file in my IBL, I get very bright pixels fireflies on my objects.

If I save this down to an EXR file in photoshop these Fireflies or bright pixels go away.

What is the best HDR, EXR file type to use with Arnold in 3Ds max? Is it better to used a clipped or unclipped hdr map. If it is unclipped how do I get the bright pixels from displaying on the objects.

skydome
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Michiel Van Gasse avatar image
Michiel Van Gasse answered ·

teapot-hdr-testl.zip

Here is the adjusted scene, I don't have noise.

I've used barcelona rooftops as a hdri from this website: http://www.hdrlabs.com/sibl/archive.html

Of course the settings will be different from other hdri maps and scene situations.

Have a look at it and do let me know if you have questions. ;)


teapot-hdr-testl.zip (663.6 KiB)
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Shane Deters answered ·

Thanks for the help, I will take a look at it. It looks good. I see the biggest bang to get rid of the noise is to change the Light source Exposure, then crank up the Camera's exposure. Would be able to explain to me why this helps? Thanks again for you help.

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I like to use more real-world values, like if you take a picture. Arnold is physically based, so its best to do it like that. Also a to low EV value with a to high light intensity will add noise, probably you get out of range of your hdri map. Or blow it out. And a higher specular samples, because your scene contains a lot of metal/indirect specular. You can render with a lower EV value, but then you need a lot of specular samples witch will increase the render time a lot.

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Shane Deters answered ·

One more quick comment, I upped the camera AA sample to 10 the noise starts to clear up. But as this is done, the render times skyrocket, looks like it will be a balance of what looks ok and render times. Once again thanks for all of your help on this. !!

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Shane Deters answered ·

Thanks for the feedback, Check out this zip. Please apply your hdr map to this scene, teapot-hdr-testl.zip I tried doing what you mention, but I still get bright speckeld noise. I really do appreciate all of the help. I will try to get a small clip of what I am trying to do. Maybe it is my hDR file. But each one I try I get similar noise issues, except if it clipped. Maybe clipped is the way to go.


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Michiel Van Gasse avatar image
Michiel Van Gasse answered ·

The first one is with 1 sample. There is some noise on the lid. The second one has an higher number. So increase it until it is resolved in your scene. It will also help with your flickering. Assuming that this is your only light source. I leave the "lock sampling pattern" off in my animations. The flickering is due to inefficient sampling probably.(can't really say without seeing the rendered result) You probably also want to increase the resolution from 1000 to the resolution of your hdri.


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t1.jpg (125.0 KiB)
t2.jpg (79.7 KiB)
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Shane Deters answered ·

Thanks for all of the help. The goal of what I am working on would be a animation. Before posting this question, I was having a terrible flickering noise in my animation, then I found an answer on these forums to "lock sampling pattern" switch which is a huge fix for what I am working on. I need to keep my render times down, per frame. I can't upload my HDR files, they are over the 2.0 meg file size. I attached my MAX file I deleted everything but teapots. Please toss a HDR map into the Arnold light texture slot. My Goal is to have a floor reflections, black background, and some really nice lighting and reflections.


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Nicholas Carrington answered ·

@Shane Deters I see need more specular samples as you are try to render higher brighter reflection / light values with unclipped. The hdri is not being limited / clipped. Unclipped alows you to get more specular "pops" but you have to render with more power/ time/ samples. Hope this helps. You can render clipped then use post fx to "pop" those highlights.

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Michiel Van Gasse answered ·

I've used both HDR and EXR without a problem. It should be unclipped.

Try using a free hdri image from the internet and see if the problem still exists.

If so make a small template scene with it so we can see what the problem is. (teapot + hdri map)

Nicholas also mentioned : Clamping (Firefly Filtering) as a quick fix.

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Shane Deters answered ·

withclipped-hdr-1.pngunclipped-hdr-1.png

If you look at the images both are rendered the same I just changed the hdr map from being clipped, to being unclipped.

I have the AA samples clipped at 5.0 for aa max value and indirect max value 5.0 also. I am not clear on what these values do.

Thanks for the help on this.


withclipped-hdr-1.png (146.0 KiB)
unclipped-hdr-1.png (205.0 KiB)
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Nicholas Carrington answered ·

Try the Clamping (Firefly Filtering) options in your arnold settings. Please post a screen shot of your problem if you can.

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