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gerhard-thirion
Feb '10

Hi

I have recently started do some work for a jeweller rendering his CAD designs in Maya. I am having some trouble with getting them as perfect as he envisions them.

My first problem is the metal shaders. In my opinion they are quite near perfect, but my boss is not as convinced as I am. I found some nice metal shaders online and tweaked them until I thought they were quite close to what the yellow and white gold looks like that he needs.

Second is that he wants perfect diamonds, which I am finding very difficult to produce. I am using a glass shader that i downloaded, I pushed up the refractive index a bit and the refractive rays and the reflective rays in the hope to get a nice diamond going. It looks very nice in my eyes but it's not easy to impress a jeweller. 

My boss gave me a some reference images, which he wants met to emulate perfectly. I will add them below with my results. My question is; what next!?how do I change these shaders to get the right results?

This is the Yellow Gold example my boss gave me to work off he wants my results to perfectly emulate this image.

This is my result. Basically my boss gave me this design in .OBJ format and I had to clean up the geometry and add my shaders and materials and render as close to the example as possible. Note the band is cylindrical so the results might look a bit different.

This is the White Gold Example I got from my boss.

This is my attempt at white gold, it is the same .OBJ as above only with a white gold material applied.

Additionally I made two plain rings to see the results with rectangular bands so I could closely match it to the examples.

This is the plain yellow gold band.

So this is all my images. If you could please just have a look and comment and also help me with some advice as to how I can improve on my results.

Thanks in advance.

GT 

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    Feb '10

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    Nov '18
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joojaa
Feb '10

How much physics do you know?

For starters you need to account for chromatic aberration, total reflections. Also you nee dto pump your max refelections much higher. Also you probably nee dto have a iterresting enviromnet to react to.

chris-rogers
Mar '10

hey

the environment is really important for reflective and refractive shaders.  make sure there is geometry or a cube/sphere mapped with an envirorment texture.  lighting the scene with an HDR image that matched the reflective shaders would be ideal.

great modeling and lighting

chris

chris-rogers
Mar '10
joojaa

the example image has envirornmental reflections, the blue, so that would add a lot of realism.

rendering each pass separately will help you get the exact exposures you want, ie: in the example, the brighest pixels are in the diamond and the band isnt that bright, so if you render out the separate objects in separate passes you have fine control over that.

the posts that hold the diamond in dont seem shaded correctly.  lacking an ambient occlusion pass? or shadows on a neighbor?  in the example, the sides toward the diamond are much darker.

Like Jooja said, try using a photon mapping renderer (mental ray) to get more physically correct light., but still try to combine the elements in photoshop to get them exactly right instead of re-rendering over and over and over

also, a slight bit of depth-of-field (blur)  on the far part of the band might make it seem more like a photo.

are there smudges on the diamond in the example?

joojaa
Mar '10
joojaa

Well the greatest problem with getting a diamond look good is as follows:

a diamond happens to work alike a prism, it total reflects light by bouncing it back to sender it also has some in purities so it eats light passing tough, now this is tricky, since shading models as a general rule dont do:

total reflection
chromatic aberration

Now atmospheric effects such as the impurity they often do make.

So this means you will need to probably build the shading networks yourself, total refection is easy but chromatic aberration is just downright insane on your render times.

Now then you have a additional layer of complexity because you need to actually get right color levels for the reflection to get right exposure.

Nothing of this is very hard just have to be quite in tune with how physics work to get it correct. As you need to be able to stage tests to get the desired effect.

try using a photon mapping renderer (mental ray) to get more physically correct light

Doesn't help the shader need to be fixed for this to help, But yes you will need that once you get the shaders working to get he caustics going.

There is a alternative way. and that's to lie and cheat with simpler materials.

PS: As for the references, the blue MIGHT be absorption talking.

PPS: also the metals can not rely just on the env map they also need to reflect the object itself.

way too much PS:es: ambient occlusion is not applicable of these materials as a strategy, because they are highly polished and have VERY small diffuse components.

8 years later