Newbie On Trial Questions


#1

Hi all. yesterday was my first day trying out Krakatoa. I use Maya 2015, and Realflow 2014. I’m primarily a single man studio that does a lot of fluid/ocean sims. I have a lot of questions on Krakatoa that I spent all day yesterday trying to figure out and research but some i am just totally in the dark on. Please bear with me if i sound stupid, but if i don’t ask, I won’t learn and can’t make a justified decision of whether or not to purchase Krakatoa.

So:

  1. Is KMY designed to render ocean surfaces or just secondary (splash. bubbles, etc) particles?

  2. Is there shading involved? Or is it just the few parameters that are within the render settings panels? Like shouldn’t particles of that nature have some reflectivity/refractivity/etc?

  3. The whole Magma thing kinda confuses the heck out of me. I’m not a mathematician by any means. i use node based compositing but as far as knowing what to use to calculate vectors and things like that, i am absolutely clueless. Does this make KMY NOT the right software for me?

  4. The PRT Surface function…Is there a use for it? In one of the videos, it mentioned that it was a good way to visualize settings and capabilities of KMY. But can you actually use it to convert geo to particles and form a particle system from that? In other words, the Mini Cooper scene. Was the simulation of the particles blowing away done using KMY or another software? In Realflow we’d model the Cooper, use a Fill Object emitter, and then add the forces to the simulation to blow things away as done. But is that what was done here or does KMY do this somehow in an easier way?

  5. My biggest hurdle is the shading. In order to get shading like in the Edward Cullen example from Twilight on one of the tutorial videos, does that have to be done with Magma?

  6. I think my goal would be to shade the particles as if they were real geometry but i think i might be off the wall for thinking that. Right? :slight_smile:


#2

You are right, there are no stupid questions, just stupid answers. Hopefully my answer won’t be one of those :wink:

Krakatoa was not designed to do a specific thing. But it is of course not a general-purpose renderer like V-Ray or mental ray either. It was designed to load and render very large amounts of particles as points in relatively short render times. Most of the time it is used to generate passes to be composited with other elements, and some people just like its look and speed when producing those kinds of elements. So I would say that rendering splashes is relatively common, rendering surfaces makes little sense as they rarely come in the shape of millions or billions of points.

Here is a rather simple example of a Naiad fluid sim where Krakatoa was used mostly for the foam and bubbles. I suspect you might be familiar with it, but it shows how an artist used Krakatoa to enhance the look with an additional element:
vimeo.com/44535646

There is shading involved, but it does not perform any raytracing at this point. Krakatoa calculates light attenuation through a volume of particles to produce volumetric shading and shadow casting from one particle onto particles behind it. The particles can have a few shading-related channels needed for the volumetric shading equation - (Scatter) Color, Emission, Absorption, Density, Normal, Tangent all can be used to calculate the amount of light scattered into the eye, the amount of light passing through the particle, the amount of light it blocks along the light path and camera viewing direction, the amount of light emitted by the particle itself etc. In the default Isotropic shading mode, light is scattered equally in all directions. Some of the other shading modes might make little sense in volumetric rendering, but people asked for them, so we added them (e.g. Phong). Others were needed in production (e.g. Marschner Hair Shader). Last but not least, the ability to texture every particle or camera-project images on moving particles allowed us to use Krakatoa to render moving 3D pixels, as you mentioned in your later questions below…

Magma is a node-based channel editor. It should be rather straight-forward to do most operations in it if you are familiar with compositing, as it performs mostly basic operations between values stored in the particles - just like an Add or Blend node in a compositing application could merge values from pixels of two images, Magma can do that with values of particles. Of course, it also has a bunch of mesh-related operators to do raytracing, point sampling etc, but I feel it is much simpler than, say, Softimage’s ICE which was a full-blown visual programming interface. Magma is a tool Technical Artists and TDs would love, but it is my conviction that any artist could learn to use (and love) it… It can help with the shading part, too (as you can control values per particle with it). In fact, I find Magma much easier to use than Maya Expressions… But that’s just me.

The PRT Surface and PRT Volume objects are mostly used to generate a static cloud based on a (static or dynamic) mesh. The actual points are not animatable like a particle system. The Mini Cooper scene was done using a regular particle system that was saved to PRT using Krakatoa and then reloaded and further processed with Camera Projection etc. Since you have RealFlow, you could do most of the simulation work there and then get the data over to Maya+Krakatoa for data massaging and rendering.
I personally find the PRT Volume and Surface useful when I need environment objects from the scene to participate in the Krakatoa rendering (e.g. catch shadows etc.)

In Maya, it would require some Magma to do the camera projection. In 3ds Max and Cinema 4D, the workflows for producing camera mapping are different and do not necessarily require Magma (Krakatoa C4D does not even come with Magma yet). But there was barely any shading (beyond putting the texel color from the plate onto the particle and making it stick) in that example.

Right. Krakatoa particles are pixel-sized points (depending on the filtering, they might fill more or less pixels), but they are not geometry. That’s what makes them fast. They can be thought of as points of a surface or volume (like molecules) with certain properties though - in Phong mode, each particle reflects light as if it was a tiny plane with a Normal vector. If you had a PRT animation where the Normal is changing over time because the particle is spinning, the cloud would sparkle.
Btw, the Phong mode was actually added during tests for the Nanomites rendering in “GI Joe: Rise Of Cobra” because it was assumed a cloud of nanobots would have a metallic shimmering look. But the director did not want that look, so we ended up with a new shading mode in Krakatoa for you to use :slight_smile:

I don’t think I really helped with my answers, but I guess the moral is this:
Once your evaluation ends, you will probably know better than me whether YOU want or need Krakatoa in your workflow :slight_smile:
Most people get into Krakatoa because they know they want it. I am sure there are a lot of artists that do not need it.
You just have to figure out if you are one of the former group, or of the latter.

Either way, have fun exploring!