Well, as you might have guessed, caustics converge very slowly in cycles- meaning, if you want them to look good, you will need many samples to get rid of fireflies. Clearly this is why the ‘no caustics’ button is available in the renderer- a must if you’re using cycles for animation.

But: shadows from e.g. a glass monkey look awfully dark without caustics. Witness here:

So what to do? An ‘obvious’ trick is to use the incredible ‘light path’ node in the material node editor. Mixing a transparent shader and a glass shader using the ‘Is Shadow Ray’ output means that only shadows will use the transparent shader, while the rest will use the glass shader. This allows us to dial in the opacity of the shadow by varying the darkness of the transparent shader. Cool!

But, in the back of our minds, we all really regret missing those caustics. Enter the trick discovered on BA for making lights: use the dot product of the incoming and normal rays (this is basically getting the angle between the normal and the light ray) to a ramp. The multiply node allows to increase or decrease the intensity. Voilla! totally unphysical, yet very acceptable caustic effects, without the fireflies.

pretty good looking. It’s not ever going to look exactly like the real thing (obviously) but it is usually enough. The node tree for the setup? A mere bagatelle:

Our main production server just went down (It’ll be fixed soon) so I thought ‘good excuse to post on the blog’. We’ll be working through the downtime – this mainly hurts our ability to exchange files, most of us are working off local files anyway- but it will be a relief when things are back to normal.

Current tasks are animation, texturing, lighting. We’ve got some awesome new team and I’m looking forward to the days to come. As we’ve been doing online weeklies, each one has had a banner image – just a random image from the project folder or whatever I happened to be working on at the time. I thought I’d upload some here:

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Calling all students (18+), recent graduates, and professionals wanting to ply their 3D skills in libre software:

Join Bassam and the URCHN crew this autumn on the Tube Open Movie production, hosted by the Bit Films animation incubator at Hampshire College, Massachusetts. Helmed by Chris Perry, formerly of Pixar and Rhythm & Hues, the program draws together a lot of talent, so although the internships are unpaid, it promises to be a very stimulating and fruitful space. These positions offer an opportunity to improve your skills, develop your reel, and make useful contacts in the industry.

The official internship period runs from Monday September 24, 2012 through Friday December 14, 2012.. Applications are due (via email) no later than Friday September 14, at 5pm (EDT). We understand that this may be short lead time for those needing to make visa and travel arrangements. Because the project is ongoing, the internship period is flexible; if in doubt, apply!

Please read carefully the open positions announcement and FAQ! Have more questions? Email us: internships@bitfilms.com