Displacement Vs Arnold

[musashidan]

I'm just running some tests between Corona and Arnold regarding displacement quality and I have to say that in this particular test Arnold results are far superior.

Scenes are identical. Tess plane/texture maps/lighting. The Arnold results look so much more realistic. Corona seems flat with little contrast or microdetails. It seems washed out and blurry. Arnold has nice tonal contrast and details are sharp.

I'm running Corona 3, but I'm not seeing the Autobump feature that should be present. Isn't it supposed to be in V3?(I'm guessing it's hidden because it should always be on) Arnold has Autobump enabled. Corona pix is set to 1. I also 2x the strength of the Corona normal map which I shouldn't have to. Am I missing something here? The only thing I thought could be the issue is the way Corona shader handles IOR related to glossiness/roughness. I'm not a big fan of inverted the roughness map. I wish Corona would move over to the metal/rough shading model that every other renderer is using now.

Arnold


Corona

[pokoy]

Autobump in v3 is enabled by default, the checkbox is 'hidden' the Devel Tab which you can make visible by checking it on in Corona's general settings.

Arnold's displacement works great indeed. It's faster and looks quite good without too much tweaking, also their autobump is pretty effective while it's a bit... dull in Corona. It's just less effective for some reason than in Arnold.
I feel Corona's devs are aware of the shortcomings, hopefully they'll keep improving it.

[romullus]

If you really want to compare displacement, then you should render with grey material, preferably with same camera and lighting setup. From your examples it's hard to tell what's really going on, for me it seems that Corona uses softer image filtering by default. Also, image contrast hardly has anything to do with displacement. Render the same scene in Corona and Arnold, with autobump enabled and disabled in both renderers, so that images could be compared side by side.

[musashidan]

Glad it's not just me then. :) You know when you've been staring at the computer for way too long......

Makes sense with the Autobump always being on in the background. It's as I suspected. I just saw the other thread about displacement and it does seem that the devs are aware of the shortcomings.

I suppose I'm just on the cusp of deciding whether I want to completely switch over to Arnold when Max 2020 releases. It's one less subscription to pay every month, I suppose. Corona will be sorely missed if I jump ship, but Arnold for Max has really come along nicely(I'm on the Max beta) and it's FREE!! :)

[musashidan]

If you really want to compare displacement, then you should render with grey material, preferably with same camera and lighting setup. From your examples it's hard to tell what's really going on, for me it seems that Corona uses softer image filtering by default. Also, image contrast hardly has anything to do with displacement. Render the same scene in Corona and Arnold, with autobump enabled and disabled in both renderers, so that images could be compared side by side.

Image contrast in the sense that the Arnold render has more tonal depth from whatever way the lighting affects the displacement. I'll do some grey shader tests.

[musashidan]

Grey shader test shows it up even worse. I had to turn off the HDR and add a harsh direct light to Corona before the displacement would even show. Arnold by comparison shows great detail with the HDR. Also, the plane in Corona is tessellated 4X that of the Arnold plane.
Autobump is always on by default in Corona, as we've discussed above. You can't turn it off from the UI.

Corona HDR


Corona direct light


Arnold HDR

[TomG]

Autobump is always on by default, but it can be turned off in the UI (Enable Devel/Debug stuff, and there's a checkbox there for it). Doing so is not recommended, but if you want to do it for testing and comparisons, the option is there.

[musashidan]

Thanks, but I don't see why I'd ever want to disable it. :)

Any thoughts on the results above as a Corona team member?

[TomG]

Nothing from me :) Testing is not my main focus, and this one I am not currently investigating.

[musashidan]

Nothing from me :) Testing is not my main focus, and this one I am not currently investigating.

No problem. Sounds fair. :)

[romullus]

Grey shader test shows it up even worse. I had to turn off the HDR and add a harsh direct light to Corona before the displacement would even show. Arnold by comparison shows great detail with the HDR.

Are you sure, that HDRI is setup correctly in Corona version? It certainly doesn't look so. That might explain your worse than expected results.

Also, the plane in Corona is tessellated 4X that of the Arnold plane.

Geometry doesn't have to be pre tesselated for corona displacement. You can get great results on a single poly plane.

Your testing setup just makes hard to compare displacement pixel to pixel. Here i made quick demonstration, how proper comparison should look. Same camera, same lighting, same looking material. You can open pictures as  photoshop layers, or as tabs in your browser and clearly see difference by alternating between them. Sorry, i couldn't compare to Arnold, my max doesn't have it.