KeyShot Forum

Technical discussions => Lighting => Topic started by: AlexBBM on May 22, 2014, 11:25:06 pm

Title: HDR problem in reflections
Post by: AlexBBM on May 22, 2014, 11:25:06 pm
Hi everyone!
(http://images.vfl.ru/ii/1400830584/36083774/5215678.jpg)

(http://images.vfl.ru/ii/1400830584/df3618b5/5215679.jpg)

How can I resolve this issue? This model and HDR has no problems with rendering in Modo...
Title: Re: HDR problem in reflections
Post by: Esben Oxholm on May 22, 2014, 11:32:26 pm
What if you change the angle to the same as in the modo-render?
From your images it looks like there's a "bulge" in the model, but because of the angle, it's more visible in the keyshot render.
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 23, 2014, 02:29:01 am
I see this problem and to other similar products, regardless of the angle. In Modo good from any angle.

(http://images.vfl.ru/ii/1400841796/22656b92/5217294.jpg)
Title: Re: HDR problem in reflections
Post by: DriesV on May 23, 2014, 02:56:09 am
Interesting.
Can you upload your KS scene (ksp) or CAD/model?

Dries
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 23, 2014, 03:09:02 am
This is my first steps with Keyshot, sorry
https://www.dropbox.com/s/jwf6xm2h2dwk9c0/Test_Steel.ZIP
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 23, 2014, 03:10:54 am
Compare with Modo

(http://images.vfl.ru/ii/1400844414/67ad0369/5217618.jpg)
Title: Re: HDR problem in reflections
Post by: edwardo on May 23, 2014, 05:08:18 am
I haven't looked at the zip you uploaded yet, but this looks more like issues with the model (surface continuity looks just tangental/G1 in the keyshot images). Was the model built in MODO, and is MODO somehow able to interoperate the model (smooth it out) in a way keyshot doesn't/can't?

Ed
Title: Re: HDR problem in reflections
Post by: DriesV on May 23, 2014, 05:24:36 am
This looks like an issue with normals.

I imported the OBJ into modo, saved out as FBX (2013) and reimported into KS.
I think this removes the issue.

Dries
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 23, 2014, 06:28:52 am
2DriesV: I also thought the problem in normals and tried different ways to import\export model (FBX 2010, 2013, Collada, OBJ). It does not give perfect results on your render this defect is present. Used Level in PS for visible:
(http://images.vfl.ru/ii/1400855851/51f81295/5218931.jpg)

2Ed: Model in modo from SDS was frozen and cleaned (the standard way prepare model for export). I tried to remove the extra faces at the site, but it does not work. Reverse import OBJ to Modo as well rendered in the Modo.

If you use another editor, not Modo, can you try to make this model (very few clicks) and try to render in Keyshot?
Title: Re: HDR problem in reflections
Post by: DriesV on May 23, 2014, 07:23:32 am
Modeled the cap in SolidWorks. Base shape is revolved spline. Imported through beta importer.

Dries
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 24, 2014, 01:28:43 am
The problem in the export from Modo. Thank you for your help.
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 24, 2014, 04:06:03 am
I continued to study. Model of DriesV has a rounded shape to the troubled area, so do not see the problem. I made ​​a model in 3DMAX (primitive, because I do not know the editor). Imported to OBJ.
I also noticed that the problem areas depends on the distance to the camera.

Click on it:
(http://images.vfl.ru/ii/1400933548/1bd405a4/5225118_s.jpg) (http://vfl.ru/fotos/1bd405a45225118.html)



This model in Modo render.
(http://images.vfl.ru/ii/1400933916/81c4472c/5225144.jpg)
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 26, 2014, 12:58:50 am
some ideas?
Title: Re: HDR problem in reflections
Post by: DriesV on May 26, 2014, 08:12:04 am
Okay, here's another test I did.
SolidWorks and converted FBX model attached. You should be able to import them into KeyShot. Both seem to work great in the 'area of interest'.

Dries
Title: Re: HDR problem in reflections
Post by: AlexBBM on May 27, 2014, 05:27:17 am
Can you try to make a bevel not round, as in the image below? And also remove the white table. Thx for help. Pardon of my eng.

(http://images.vfl.ru/ii/1401197918/cc0326b2/5263700.jpg)

(http://images.vfl.ru/ii/1401198143/fa42e0ff/5263725.jpg)
Title: Re: HDR problem in reflections
Post by: DriesV 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
Title: Re: HDR problem in reflections
Post by: AlexBBM 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.
Title: Re: HDR problem in reflections
Post by: edwardo 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
Title: Re: HDR problem in reflections
Post by: AlexBBM 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:
(http://images.vfl.ru/ii/1401364630/b0eb3130/5282714.jpg)

Long distance, bad result:
(http://images.vfl.ru/ii/1401364521/d8511761/5282708.jpg)

In Modo, I can be adjusted this using "Angle smooth" in material
Title: Re: HDR problem in reflections
Post by: AlexBBM 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?
Title: Re: HDR problem in reflections
Post by: andy.engelkemier 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.
Title: Re: HDR problem in reflections
Post by: AlexBBM 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).
Title: Re: HDR problem in reflections
Post by: andy.engelkemier 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.
Title: Re: HDR problem in reflections
Post by: AlexBBM 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... :-[)

(http://images.vfl.ru/ii/1404146693/8e47cd0d/5586646.jpg)

(http://images.vfl.ru/ii/1401364521/d8511761/5282708.jpg)
Title: Re: HDR problem in reflections
Post by: andy.engelkemier on June 30, 2014, 12:15:33 pm
Maybe I'm not seeing the problem. Here is a randomly googled photo showing similar behavior.
(http://ecx.images-amazon.com/images/I/41f5oI1ar%2BL.jpg)

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.
Title: Re: HDR problem in reflections
Post by: AlexBBM 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.

(http://images.vfl.ru/ii/1404164855/41a3005d/5589266.jpg)