I am trying to make a realistic orange juice in a glass scene, but the glass seems to mess things up, as can be demonstrated by enabling "no caustics"

Without glass with caustics, with the glass without caustics, and with the glass with caustics

enter image description here enter image description here enter image description here

As you can see, the glass is making the orange juice darker and noisier. (all were rendered with 100 samples)

My question is, what is the best (fastest, nicest looking) way to render with the glass? (and still have the effects of refraction etc.)


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    $\begingroup$ Try to keep your posts limited to 1 question. $\endgroup$ – iKlsR Jun 20 '13 at 20:02
  • $\begingroup$ The title sounds like a tutorial request, but your question sounds like your asking how to fix the dark glass. Can you specify one question? $\endgroup$ – CharlesL Jun 20 '13 at 20:03
  • $\begingroup$ Should I split this into two posts? (one for the dark glass and one for the lightening effect) $\endgroup$ – gandalf3 Jun 20 '13 at 20:10
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    $\begingroup$ @gandalf3 preferably, one is related more to shaders and the other to lighting. $\endgroup$ – iKlsR Jun 20 '13 at 20:14
  • $\begingroup$ @gandalf3 yeah, that would be great :) $\endgroup$ – CharlesL Jun 20 '13 at 20:26

Excuse my technically incorrect explanation. I'm stating this from an artists perspective and don't know all the math behind all of it. :P

Glass uses a lot of processing power, and there's really not a way to render faster. I can however suggest a few things that will make the glass look better.

More Light!

This is probably the biggest issue I see when glass looks dark and yucky. Glass refracts/reflects light all over the place. Glass doesn't really hold much color itself. It's mainly just a light-bender. That's what gives it a realistic look.

Use an Environment Map

As stated before, glass just bends light. The more types of light it has to work with the better. Environment maps are one of the easiest ways to make glass look realistic. And it's not too much work to put one in the scene.

Set the color to White

Setting the color of the material will tint the glass with that color, so if you leave it with the default "almost white" grey, your glass will be darker. Set it to full white to have the maximum transparency.

You do need caustics

I don't know exactly what they do, but I know it has something to do with light bounces. You need caustics if you want the light to go through the glass.

From Wikipedia:

In optics, a caustic or caustic network is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface.

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    $\begingroup$ Another option is to increase the min/max number of light bounces. Since glass/SSS/glossy surfaces all deal with lots of light bounces, I turn those settings up really high whenever I have those materials. $\endgroup$ – Gwen Jun 21 '13 at 17:57
  • $\begingroup$ I know I need caustics, (a caustic refers to the light that is refracted/focused/reflected through/off some material such as glass and illuminates another surface) so no light the is refracted through the glass illuminates the orange juice. the reason I added that is to demonstrate that the glass is what is affecting it. also the glass is at white. I agree I probably need more light :P $\endgroup$ – gandalf3 Jun 22 '13 at 23:00
  • $\begingroup$ @Gwenn how high? this is using the Progressive integrator, right? $\endgroup$ – gandalf3 Jun 22 '13 at 23:13
  • $\begingroup$ @gandalf3 Go to Render>Light Paths and increase the settings for 'Bounces'. By default, it is min=3, max=8. You can improve the results of almost any render by increasing those values (I usually do around min=7, max=18). It adds a little time to the render, but it really makes a difference in render/lighting quality, especially in complex scenes. $\endgroup$ – Gwen Jun 22 '13 at 23:17
  • $\begingroup$ @Gwenn ah thanks. though I'm a little confused about the settings directly below it, (for diffuse, glossy etc.) It says "maximum number of diffuse/glossy/whatever bounces bounded be total maximum" does that mean that it only allows 8 of those even though they are set 128? $\endgroup$ – gandalf3 Jun 22 '13 at 23:25

Try changing index of refraction(iOR) to real value of glass.If it looks like glass shows traces of juice in it,try scaling down juice mesh a little bit(like .99) Hope this helps

  • $\begingroup$ the cycles glass shader defaults the IOR to the real value of glass (to my understanding, anyway. I supposed some glasses have different a IOR than others) and I'm 99.9% certain the juice is not intersecting the glass anywhere. (just double checked) $\endgroup$ – gandalf3 Jun 22 '13 at 23:11

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