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Diamonds

Posted: Thu Sep 13, 2018 11:19 am
by Hell948
Hi, getting back to blender I got the pleasure to discover this "new" luxCoreRender. First thing, it look great !

So, back to business. I'm into 3D jewelry modeling and I wanted to give luxcore a shot even if blender seems to have almost no recognition at all in the industry. First exercise, a simple but hard one. Making a great diamond ofc ! This is what i got after a day or two of fiddling with the new renderer...

I tried both Path and BiDir. I like the path one. The BiDir shows some more refraction in the diamond which sure looks great but the ground lost all contrast and shadows, so not so great... If anyone as any clue about what happened, let me know :)

Any crtitics or recommendation is welcome ofc.

Re: Diamonds

Posted: Thu Sep 13, 2018 11:40 am
by B.Y.O.B.
Nice renders :)
The issue with Bidir might be a bug, can you upload the .blend file with all textures included?

Re: Diamonds

Posted: Thu Sep 13, 2018 11:46 am
by Hell948
Oh is that so ? I saw someone rendering gemstones increased eye depth and light depth. Currently rendering it again with them increased from the one I posted.

Here is the .blend no textures used at all for now. Hope it will be all good ! Otherwise let me know i'll stay around :) Thx

Edit: Should I include the hdri or is in the .blend ?

Re: Diamonds

Posted: Thu Sep 13, 2018 11:53 am
by B.Y.O.B.
I'm getting a weird result when I render, the ground plane is transparent?
edit: ah, you are doing some render layer stuff.
Hell948 wrote:
Thu Sep 13, 2018 11:46 am
Edit: Should I include the hdri or is in the .blend ?
You can pack it.

Re: Diamonds

Posted: Thu Sep 13, 2018 12:03 pm
by Hell948
Nope the ground and the diamonds are on different Render Layers, should have said it my bad.

Here is the .blend with the hdri. (or is there a way to pack it into the blend ? If so idk how sorry)

Re: Diamonds

Posted: Thu Sep 13, 2018 12:07 pm
by Hell948
Ok seems like connecting the alpha output of the diamonds to the alpha over "fac" solved it. But to be honest i dont really understand why the path behaved differently if i also forgot it...

Edit: Or maybe not fixed cause it cuts the glare effect. Is it possible the background is not really transparent ?

Re: Diamonds

Posted: Thu Sep 13, 2018 5:55 pm
by Hell948
Ok so little update !

The "white / faded" effect when using BiDir got solved by turning "Convert Premul" on the alpha over I was using to mix both render layers.

Something weird came up tho. The glare effect could be applied to the diamond layer only when using Path, and it was showing up correctly once alpha overed. Not cropped to the layer mask or anything.

But when using Bidir, the glare was not "going out" from the stone. Got around applying the glare after the alpha over as my ground was dark enough .

Here is the end result, could need a little more time to render tho

Good night and thx for having looked all this up BYOB.

Re: Diamonds

Posted: Thu Sep 13, 2018 6:02 pm
by B.Y.O.B.
Sorry I had no time to look into it further today, I logged it as an issue and will look at it at some later time: https://github.com/LuxCoreRender/BlendL ... issues/212

Re: Diamonds

Posted: Fri Sep 14, 2018 6:14 am
by Hell948
Hi, no problem. Keep up the good work i really found LuxCore awesome and I really think I could pull something up good enough with it to make it accepted in a work place.

Here is the end comparison between BiDir & Path :

Re: Diamonds

Posted: Thu Sep 20, 2018 9:39 pm
by Lights_and_Shadows
If I may, I want to offer a suggestion for you :)

What I did for my gemstone renders is actually create a whole lighting studio, including lights. I started with a cube, cutting out a portion of one side to have an opening to "place" the gemstone in, as well as sticking a plane inside it to set the stones on. In addition, I added a very small amount of thickness (around 5mm or so) to the cube with the Solidify modifier, for better translucency. For the cube, I set it to glossy translucent with a light-grayish diffuse color and transmission to pure white. IOR is trivial ultimately. For that plane that is essentially a floor, I set it to a glossy material with an almost black color, the IOR set to the PET plastic preset, and roughness around 0.0010. This is basically an acrylic glass (if you wish, you could use an acrylic glass preset if it's still available in LuxCore's presets, I remember the old version had it).

For lighting, I use a combination of light emitting planes and a Hemi lamp. For my scene, I use two planes, one slightly larger than the other, and set it to Emission with a blackbody color. Daylight works best and fits the industry standard if you browse around gemstone lighting tutorials (around 5000-5500k). Scale for all of your objects is also very important - the cube is around 50cm all around, with the floor slightly smaller.

As for the gemstones, once you model one, scale it down to a realistic value for the gem you're trying to simulate. I sometimes experiment with adding a very slight bevel on top of the smaller size using the Bevel modifier. I use 4 segments usually, to simulate hard edges on an otherwise smooth stone. At this stage, do what you think works best :)

Feel free to take this into consideration, see what comes out of it :)