Render lighting looks different at different resolutions...

DEJ_Design · October 31, 2018, 06:11:59 PM

I'm having an issue with creating higher resolution renders. I'm adjusting lighting so it looks perfect in the real-time render view and taking note of the sample # in the HUD. When I generate a render using the max samples option (with the same number of samples as the realtime view) at a higher resolution, the render looks totally different, almost like the material is reflecting much less light. It's my understanding that the realtime view and max samples utilize the same engine, so at the same sample #, the images should look identical (other than the different resolution). I found a few other threads for similar issues in Keyshot, but no resolution.

Anyone have an idea what's going on here?

Edit: I added another photo to show the dramatic change in tone. The higher the resolution of the final render, the more matte the material appears and less falloff in the lighting on the surface.

Esben Oxholm · November 01, 2018, 01:15:52 AM

Not really a helpful answer, but to me the lighting look the same. It more looks like the texture scaling is different on the two different renderings. Is it possible for you to try with another bump map and see if that will behave correctly?

DriesV · November 01, 2018, 02:27:01 AM

This looks very odd.

A couple of questions:

What version of KeyShot are you running?
What kind of textures are you using? Images? Procedurals?

Would it be possible to share the scene? You can send data privately and securely via our WeTransfer. Send to dries-at-luxion-dot-com.

Dries

DEJ_Design · November 01, 2018, 02:38:05 AM

Thanks for the feedback Esben, I'll definitely give your suggestion a shot and try a different bump map.

I can upload another photo that shows the issue more clearly, perhaps with less complicated geometry. At 4K, the surface looks almost completely matte with no falloff. At my screen resolution of 1156 x 893 (realtime view), the surface looks shinier with a clear falloff. The value shift is quite dramatic and unexpected.

@DriesV, I'm running Keyshot 8.0.247 on MacOS Mojave v10.14. The material contains several of Keyshot's own textures for this, both images and procedural. I'll send the .ksp as soon as I can. Thanks Dries.

DEJ_Design · November 01, 2018, 12:27:45 PM

I did another render test, this time with a simple rectangle that's the same size as the object I was working with. The lighting setup is the same and so is the material. I think this photo shows the problem pretty clearly. Even with the same number of samples, as the resolution increases, the material appears to become more matte and the falloff of the light goes from perfect in the realtime view to non-existent at 4K. This is a huge issue because I count in the realtime view to ensure my lighting is correct before I render out at a much higher resolution...

@DriesV, you should have the .ksp for this scene momentarily...

mattjgerard · November 02, 2018, 06:57:53 AM

I'm trying to find the post where someone mentioned that for the same appearance in quality the higher the resolution the fewer samples is needed? I can't find it at the moment, but will continue looking....

DEJ_Design · November 02, 2018, 11:53:02 AM

Quote from: mattjgerard on November 02, 2018, 06:57:53 AM
I'm trying to find the post where someone mentioned that for the same appearance in quality the higher the resolution the fewer samples is needed? I can't find it at the moment, but will continue looking....

Yeah, I saw that too. It's mentioned in the Keyshot manual. Unfortunately, collecting less samples doesn't fix the problem. Luxion support got back to me and acknowledged that they could reproduce the issue, but as of yet don't know what's causing the problem nor could they provide a workaround. I'm surprised no one has noticed this yet, seeing as how this would affect everyone who outputs renders over 2K.

@DriesV, I sent you the .ksp...any idea what could be causing this?

DEJ_Design · November 03, 2018, 01:21:53 PM

I found it again...it was in the Keyshot 8 manual under Render Options.

"Something important to be aware of is that as you increase the resolution of your image or animation, each pixel covers relatively less area of the image. This means you can use a lower samples setting when rendering at higher resolutions. Note that this does not apply to rendering with area lights, caustics or interior mode as increasing samples while using those features will still increase the quality."

The relevant image was in the Keyshot 6 manual, which shows the overall image appearance shouldn't be different at different resolutions. The right shader ball is twice the resolution of the left.