2011 October | Hristo Velev

With Igor Zanic and Naiad in Belgrade! Naiad/Max workflow.

October 23rd, 2011
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I spent last week in the afterglow of summer in Belgrade, with the awesome Igor Zanic! He taught me some Naiad, and we established the workflow of shading it in Max – with Krakatoa, Frost and VRay. Check out the goodness:

Now, the way this goes – it starts with the Naiad sim. It took only 42 min with, 7.5 mln particles through a reasonably dense cell size (the grid resolution in Naiad). On top of that, a secondary sim was done for splashes, this one taking 45 min for 20 mln particles. The machine was a recent i7 quadcore, nothing spectacular.

After that, the native Naiad EMP cache was converted to PRT, and sent to Max and Krakatoa. The first element was the mesh, with Frost and VRay. That went very smoothly, being able to quickly relax a high res sim to get a smooth but detailed result was of great help. The VRay setup was very straightforward – reflective transparent 1.4 IOR shader, with some of the VRayMaterial fog for depth and a good environment map, oldschool lighting. Render times at 1280×720 did not exceed 8min per frame, and you can see the detail is astounding.

On top of that, four Krakatoa passes were rendered. An interesting thing I noted is how much shading these liquids depends on the scenario. We did another test before this one, with much calmer water, and it ended up using different type of elements, and with different weights. Fortunately Krakatoa, with its KCMs, provides great flexibility in treating the material coming from Naiad, and you can devise different schemes of shading it.

Setting up these passes was fun and a breeze. On the main one I used a normalized velocity for a texture lookup, assigning a material with a blue to white gradient in the diffuse. This makes the faster particles whiter, which looks great. For the calmer areas, putting a threshold on the velocity, setting the selection channel and deleting the slow particles looks great, to clear them up in the clear areas. Of course, you could do a red-green pass and do all that in comp. Adding a velocity driven curve to the density makes the structures more visible, very good for bringing out the detail.

Then it was the Vorticity pass. We used a custom vorticity channel we exported from Naiad, and it’s a very simple expression, Naiad is very friendly towards exporting custom channels. Again, a texture lookup and delete thresholds were enough to make this one look interesting.

The splash sim was also rendered in Krakatoa. This one looks pretty great out of the box, but again the velocity-density curve looked great in bringing up the detail. Lighting is quite important too – getting these darker deeper parts is very cool and easy with a simple 4 point light setup.

Last one was a depth pass. Loading a fraction of the original particles, and shading with the Voxel mode in Krakatoa, you can get a very useful pass that you can dial the light extinction and coloring in depth with.

Now, it’s interesting to see how much freedom there is in compositing all that. A very broad range of looks can be derived, that my very limited comp skills obviously do not showcase 🙂 You can see a breakdown and another option for comping it here: