Comparing Gold: Iray and LuxRender

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Comparing Gold: Iray and LuxRender

Postby Nyghtfall » Sat Sep 10, 2016 10:03 am

First and foremost, I did not create this thread to start an engine war. I'm simply comparing how each engine renders the same type of metal. That's why I deliberately worded the title "and" instead of "vs".

Someone at DAZ expressed frustration over the growing number of Iray-exclusive items being released. They don't have the hardware for Iray, or the skills to adjust converted mats in Reality,so they've relegated themselves to 3DL when it's available.

There's nothing special about Iray mats that prevent Reality from converting them. The only difference is how Iray and Lux render materials, and that's where some adjustments may be necessary to get the results you want.

To demonstrate their differences, I rendered a material ball using each engine's native Gold metal shader preset. I used the same ball and HDRI lighting to produce the fairest comparison possible. The Gold in the Iray render is from the DAZ Uber preset. The Gold in the Lux render is from the Metal preset in Reality. I've done nothing with the shader itself, and I used the same tonemapping for reach render:

Film ISO: 200
f-stop: 5.6

Iray and Lux use different methods of setting the level of exposure. Lux uses Shutter speed while Iray uses a combination of Exposure Value and Shutter Speed. Changing one setting in Iray automatically changes the other, so I used the following settings to get as close to the same level of exposure that I could for each render:

Exposure Value in Iray: 24.50
Shutter Speed in Lux: .050

As you can see, they render Gold metal quite differently, based on what each engine thinks Gold metal should look like.


Figure 1 - Iray Gold.png


Figure 6 - LuxRender Gold.png

Now, we'll customize the Iray mat in Reality. First, let's recap. This is the Iray version of the Gold metal shader that comes with DAZ Studio.

Figure 1 - Iray Gold.png

Let's load Reality.

This is a straight conversion of the shader in Reality. I've done nothing else. Reality didn't quite know what to do but pick up the Diffuse color and apply a Glossy mat to the ball, so we've got a few options we need to consider.

Figure 2 - Reality Conversion.png

The shader is a type of metal, and I want to keep it that way. Thankfully, Reality has a built-in material type called Metal. Just right-click the mat for the ball and ring, select Metal, and I'm done. Reality has now identified it as a Custom Metal type by automatically checking the appropriate box while keeping the Diffuse color, and applied other pre-programmed settings to define its appearance. At this point, I could just leave it alone and render.

Figure 3 - Custom Metal.png

Or, I can try making it look like the Iray version. Time to play with the Horizontal Polish under Custom Metal. It's currently preset to 9500. The reflection in the Iray version is pretty clear, so I need to increase the number. After a few tests, 9900 looks as close to the Iray version as I think is reasonabe.

Lux Version

Figure 4 - Custom Metal 9900 Polish.png

Iray Version

Figure 1 - Iray Gold.png

Now that we know how to simulate the Iray version, let's make the HDRI's details in the Lux version really pop and by maxing out the Polish at 10000.

Figure 5 - Custom Metal 10000 Polish.png


Let's try one more thing. Switch to Reality's Gold metal preset, and it's just two clicks away from what I've done. Uncheck Custom Metal, and select Gold.

Figure 6 - LuxRender Gold.png

Max the Polish at 10000, and...

Figure 7 - LuxRender Gold 10000 Polish.png

18 carat Gold with a mirror finish. Beautiful!

For extra kicks, here's the Iray version with Glossy Roughness set to .23.

Figure 8 - Iray Gold Rough.png

And with Glossy Roughness at 0.00.

Figure 9 - Iray Gold Mirror.png

The renders above are a rudimentary example of how both engines render Gold metal, and how to customize Iray mats in Reality. All that's needed is patience, familiarity with the available options, and the desire to experiment. It is by no means a streamlined process, but it can be done.


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Re: Comparing Gold: Iray and LuxRender

Postby Marcel2586 » Sat Sep 10, 2016 2:40 pm

Thank you!
this would be funny if it weren't happening to me :shock:

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Re: Comparing Gold: Iray and LuxRender

Postby Nyghtfall » Sat Sep 10, 2016 3:30 pm

You're welcome! :)

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Re: Comparing Gold: Iray and LuxRender

Postby TransformerMan » Sun Sep 11, 2016 3:49 am

An interesting visit to the metal options. Thanks!

There seem to be some form of clamping going on with Iray. The reflection never "goes to white". Looks a bit like LuxRender does with a film simulation active.

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Re: Comparing Gold: Iray and LuxRender

Postby KrollMoll » Wed Sep 14, 2016 11:43 am

Hi Nyghtfall,

Nice article, can you create a download link to the HDRI lighting file you used so I can do some tests exactly in the same environment than you?


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