Not as scientifically accurate as claimed?

[Zen]

Keyshot is a great quick renderer, but I feel like some of the materials just aren't accurate...especially when it comes to transparency materials like gems, and waters.  typically, reflections and refractions just don't seem all that realistic and lack internal refraction depth/detail.  Am I right or am I missing something?

The first image is an example of a gem I modeled, non keyshot render.  The second image is rendered within keyshot, with keyshot materials. 

It's pretty clear the first one, looks much better.  both were rendered with the same HDRI map with similar settings (i.e. same ray depth and such). 

[KeyShot]

The materials in KeyShot are scientifically accurate and have on numerous occasions been verified against actual measurements of real materials. Furthermore, KeyShot is still the only rendering engine that has been verified by CIE as computing lighting correctly.

The materials such as water and gems that you mention are particularly simple with the light scattering being described by only three laws of physics (Fresnel, Snell, and Beer-Lambert). The Fresnel equations can be derived directly from Maxwells equations.

Now the difference in the two images can come from several sources. First the camera angle is different. Second if the HDRI is the same then the mapping of colors to the display is different. In particular the first render has a lot of contrast, which typically arises from a low gamma setting. A low gamma setting may look more pleasing as the colors appear more saturated, but it leads to an incorrect display of the actual material. I recommend playing with a simpler shape at first to get a feeling for the behavior of the lighting. The current geometry is rather complex to analyze due to the many facets.

-- Henrik

[Zen]

The materials in KeyShot are scientifically accurate and have on numerous occasions been verified against actual measurements of real materials. Furthermore, KeyShot is still the only rendering engine that has been verified by CIE as computing lighting correctly.

The materials such as water and gems that you mention are particularly simple with the light scattering being described by only three laws of physics (Fresnel, Snell, and Beer-Lambert). The Fresnel equations can be derived directly from Maxwells equations.

Now the difference in the two images can come from several sources. First the camera angle is different. Second if the HDRI is the same then the mapping of colors to the display is different. In particular the first render has a lot of contrast, which typically arises from a low gamma setting. A low gamma setting may look more pleasing as the colors appear more saturated, but it leads to an incorrect display of the actual material. I recommend playing with a simpler shape at first to get a feeling for the behavior of the lighting. The current geometry is rather complex to analyze due to the many facets.

-- Henrik

Actually the differences in color you see in the first image, are post processing changes done in photoshop....I assure you, the first image looks very much the same without it, since the changes were minor (color shifting won't remove the internal refraction details, or make them anymore visible).  I can't see gamma explaining the difference either.  No matter the HDR, no matter the brightness, the second image will still look generally the same, with nothing close to the details of the first. 

The camera angle isn't that different (you just can't tell because everything is lacking detail) and regardless of the angle, it basically has the same lack of detail/internal refraction.    The light source may be somewhat closer in the second image due to the way Keyshot handles HDRi's, but the projection is the same and even under brighter circumstances, the program the first image was rendered in still wouldn't lose so much detail. 

Which do you personally think looks better or more accurate?  My money is on if in a blind test, you'd pick the first render. 




diamond, seems to be the only one that looks right to me.

I have just noticed one thing....I tried downloading some pre-made diamond 3d models to render, and I opened it up in hexagon as an OBJ, exported as OBJ, no special export settings....and even though the geometry was the same, the diamond came out looking wrong, and I'm not exactly sure why.  here's an example:

new image1:  model straight from download

new image2:  model brought into hexagon to separate UV mapping (to make each diamond separately move-able, because they originally shared the same UV domain name)

[KeyShot]

It would have been nice to know that you post processed one image in photoshop before hand, which explains the color difference.

Again, the physics of light reflection and refraction is well understood and the difference in appearance most likely comes from the geometry or camera angle.

In the second set of images it looks like you have smooth normals on the obj file. You can turn off the automatic computing of normals in the obj importer to preserve the faceted appearance.

As mentioned, I recommend you try a simpler shape like a cube to guide your understanding of the lighting, geometry, and camera setup.

[Zen]

The issue seems to be with keyshot.  Whether I export normals from my modeler or not, whether I calculate normals when importing or not, the normals seem to not display correctly.  In other rendering programs, the normals are displayed properly.

[evilmaul]

perhaps you could share the model (diamonds maybe your gem as well) with us?! we'll have a look for you before pointing fingers here and there