Yafray: How to buy Diamonds

Picture included. This is one of my first Yafray test, original res: 1600x1200. The piggy bank in the back did not came out quite as expected. I might try another HDR map and see how it looks.

fake Caustics


very nice bro, you need more “caustics?” i think they are called? its special reflections on the glass where the light is shining through the diamonds…

see how you have the reflection on the “ground” material? well there should be speckled lights where the photos hit the surface directly…

heres a link to doing that method on a gold ring, you can use the simmilar settings to replicate the effect for the diamond…


the problem is that with the current lighting setup (no lamps, just HDR based lighting) it’s hard to get caustics, since the lighting is quite uniform from all directions.

I’ll try a lamp-lit version.

wait whats HDR, in a noob im trying to find out how to do differnt lighting as im having problems with lamps and photons…

Caustic version: took me a while to work out a HDR + lamp solution that casts visible caustics.


very nice, i like it better

can you set one to render all night with like 5mill photons :slight_smile: i think it would be very cool looking, still need to know what HDR means…

looks like you got the caustics - I was going to say a low strength spot with a photon light behind it should work. or you can always turn up the GI emit strength. were you able to get them just from the HDR alone?

I would turn up the dispersion power (for prism effect), caustic depth, ray depth and reflection for your diamond so it sparkles. also maybe blur the ground plane reflection with a noise map? looks more like a ruby now, though nice render…

HDR stands for high dynamic range. it’s a little complicated but basically it’s a way of capturing all of the light in the scene, from darkest to brightest, then using a special image to emit that light back into a 3d scene. Yafray supports it and it gives very realistic lighting and reflections. google “HDR blender tutorial” and you’re bound to find something useful.

That looks very good! I love the piggy bank idea and at first glance I wondered how you integrated the CG gems into the photo background so well!

I used a variation of f/stop’s material for the quick gem render in your other thread- changing the colors and the IOR to that of corundrum… damn, I’m a nerd. If you don’t mind sharing, what material settings did you use - your gems seem to have just the right amount of transparency.

One critique: the gems are all the same cut but different sizes. The little one kills the realism IMO.

<edit> Oh yeah, this site has links to a bunch of free HDR images and info about using them or creating your own. BTW, really large HDR images will significantly slow your renders.

Guess I’ll take out the smallest one and do a re-render. Actually i spent hours trying to figure out why the gems reflect lights in a weired way, and then it hit me, I forgot to recalc the normals after modelling. Well anyways, thought i’d share so people don’t make the same mistakes.

BTW, you’ll also find the material i used for the diamond attached below. maybe i should tune down the IOR to the physically correct value, 2.4?


definetly. some more things:

change the material color to white and change the yafray absorption color to pink. Turn dispersion up to at least .4 or .5 (I like 1)with the samples to at least 25. decrease RayMir to maybe .75, .85 and ABSOLUTELY turn up your specular hardness all the way. yellow diamonds might also be interesting.

I would love to see you blend file! good diamond models are tough to find. the one I used in the thread below was a cheap fake so to speak, I just cut faces off a cone…:smiley:

(the models were incorrect but the materials worked… also raydepth wasn’t high enough

In the modelling support forum, where mpan3 deftly dodges a kick from me, there are links to both excellent (real gem cutter’s files) 3D models, as well as a program, GemCAD, that will allow you to design your own gemstones.


I need to confess that the caustics is created in post-processing… I can’t seems to get visible caustics with just an HDR image. (maybe i need lamps?)

Yes, you need at least a photonlamp.