Author Topic: HDR problem in reflections  (Read 11725 times)

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Offline DriesV

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Re: HDR problem in reflections
« Reply #15 on: May 27, 2014, 01:57:52 pm »
Hey, now I'm actually getting the same result. :)

I'm getting a smudgy reflection across the bevel.
I tested with NURBS rendering (of the direct CAD model) in KeyShot 5 and then the reflections are perfect.

Dries

Offline AlexBBM

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Re: HDR problem in reflections
« Reply #16 on: May 28, 2014, 01:38:00 am »
Hmmm... KS5, NURBS... it's a bad bad news for me, Modo is polygonal editor. I like KS, but tiny trouble kill all  :)  Thanks for the help.

Offline edwardo

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Re: HDR problem in reflections
« Reply #17 on: May 28, 2014, 03:37:46 am »
can you not just try to sub-divide your model a few times and see if that helps?

Ed

Offline AlexBBM

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Re: HDR problem in reflections
« Reply #18 on: May 29, 2014, 03:43:58 am »
It has improved the result, but not to an acceptable. At short distances from the camera bug was gone, but at long range it can be seen. And yet, strange effect on the left screen sharpening light and dark on the right, anyway.

Close distance,  good result for KS:


Long distance, bad result:


In Modo, I can be adjusted this using "Angle smooth" in material

Offline AlexBBM

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Re: HDR problem in reflections
« Reply #19 on: June 18, 2014, 04:10:04 pm »
This is a real problem, hope a solution in the near future? Need to report a problem with developers KS?
« Last Edit: June 18, 2014, 04:13:04 pm by AlexBBM »

Offline andy.engelkemier

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Re: HDR problem in reflections
« Reply #20 on: June 26, 2014, 06:07:11 am »
The model you are testing actually has a bit of a wobble in the normals. In 3dsMax I relaxed the model slightly, then subdivided the model so you're actually sending enough tesselation, and it comes out perfect.
Unfortunately I'm unfamiliar with modeling in Modo. But from what I understood is it's mostly SubD poly modeling. You should just be able to increase the subdivisions.

Also, I worry about your scale a little bit. Either the OBJ didn't keep the information properly, or you are working with an object that's total size is 1mm. Because that's what it came in at, which would mean your radii are about .001mm. Given that most poly modelers tolerance is no more than .00001 units, that May be why you are having normals problems. Make sure you're working in actual scale when hard surface modeling.

Also, it doesn't look you are comparing apples to apples with your render from Modo. Is no one else seeing the exact same wobble he's talking about in both renders? It's just the environment is more blurry, so you can't see it as clearly. You can see a slight smudge in the same polygon string though. When I brought that in Max that's exactly where the normals get wonky as well.

One last thing to note also. Others have pointed this out in a roundabout way as well. The best way to get a Really crisp straight line reflection is with an actual object, not the HDR. Use the HDR for lighting and quick reflections. But when you want a really crisp line, sometimes you just have to grab an object.

Offline AlexBBM

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Re: HDR problem in reflections
« Reply #21 on: June 29, 2014, 06:06:42 am »
2andy.engelkemier: Thx for reply. See post #15, DriesV got the same result. Subdivision surface slightly improves the situation, but does not completely solve the (post # 18, far and short distance). Also in post # 18 shows the problem of light \ dark transition on a sharp edge. I think it's a problem when working with KS HDR, or export from Modo (I tried different formats).
« Last Edit: June 29, 2014, 06:21:24 am by AlexBBM »

Offline andy.engelkemier

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Re: HDR problem in reflections
« Reply #22 on: June 30, 2014, 06:01:07 am »
I still think it comes down to mesh density. The first render in post #15 looks like the mesh is very loose. The NURBS render is tessellating so that the mesh is higher quality, which you Can do in your software.

If you assign straight chrome to your cap in Modo and render it with the same environment does it look better? In your example you used a material/environment that was softened so you wouldn't see any issues. I would bet that you'd get similar results. The software has to bend the environment over a flat surface as if it is curved. The smaller those surfaces are, then less it has to bend.

Offline AlexBBM

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Re: HDR problem in reflections
« Reply #23 on: June 30, 2014, 08:32:05 am »
That mesh density of post # 18. I used Modo and KS the same studio that is as close as possible the conditions of render. In Modo no problem using HDR with any sharp angle surface. And how can you explain the strange behavior of the light\dark shift reflection on sharp edge? (Pardon, my Eng is too poor... :-[)





Offline andy.engelkemier

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Re: HDR problem in reflections
« Reply #24 on: June 30, 2014, 12:15:33 pm »
Maybe I'm not seeing the problem. Here is a randomly googled photo showing similar behavior.


The only way to avoid reflections that do that is to make Only curvature continuous surfaces. For your surface, you wouldn't be able to accomplish that with flat areas. As soon as you hit a flat area the reflection will take a sudden change in direction. If those meet from two different angles, it creates a sort of spike as you see in your render. That is the physically correct behavior. Find some more highly reflective cylindrical objects and you will notice the same thing there. Chrome faucets also illustrate this well.

Offline AlexBBM

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Re: HDR problem in reflections
« Reply #25 on: June 30, 2014, 01:26:57 pm »
I understand the idea. It is a symmetric object screens HDR symmetrical too. Camera in the center (in the picture is a little bit wrong, but even if the camera rotate, then the result will be the same). Left I see white peak, and right on the edge of black peak. When I rotate the camera on the left side will always be white peak, and on the right side always is black. What is it? You can try create object in your CAD program and test it.

« Last Edit: June 30, 2014, 02:37:40 pm by AlexBBM »