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Particle Rendering Workflows In Krakatoa For CINEMA 4D

Last edited on April 11, 2014

   

Introduction

Particle Rendering  (a.k.a. Point Rendering) is the original rendering mode of Krakatoa where each particle is considered a pixel-sized point. Krakatoa also provides a Voxel rendering mode which can be used as alternative in some cases.

Pros And Cons Of Point Rendering

The main benefits of using particle rendering are: 

  • Very fast rendering
  • High sub-pixel detail and very wispy plasma/smoke results can be easily achieved at mid to far distances to the camera. 

On the negative side, since the particles have no world-space size, moving in too close to the point cloud reveals its point-based nature as the particles do not change their size. Also, they will not blend into a cohesive cloud anymore at short distances, and flying through such a cloud does not produce the expected results. In these cases, the Voxel mode is the preferred approach.

The Particle rendering mode typically requires more particles than Voxel rendering to produce solid-looking results, but is usually faster. 

Workflow Considerations

In Particle rendering mode, the particle data is loaded into memory, illuminated by every light and then sorted in camera space and splatted back to front using the current Filter Mode.

The illumination sorting and drawing as well as the final pass sorting and drawing are all multi-threaded and scale well up to about 8 cores. Adding more threads does not increase performance in a linear manner due to the overhead of managing multiple buffers, one for each thread. Rendering will be faster with 16 cores when compared to 8, but not twice as fast.

Thus, when making a hardware purchase decision, going for more (and fast) memory is recommended over 16, 24 or 32 cores.

Rendering in Particle mode generally requires a very large number of particles, typically much higher than it is comfortable to work with directly in CINEMA 4D. For this reason, it is usually a good idea to bake the particles to multiple PRT sequences using the PRT Saver option in the Renderer > Krakatoa > Output tab. This will create multiple "Partitions" (also known as Wedges) of the same particle system. They can be combined by a single PRT Loader object which can be transformed, freely retimed and set to display differently in the viewport and at render time. Typically, a fraction of one Partition will be displayed in the viewport, while rendering 100% of all Partitions. This allows for a very fast real-time scrubbing in the scene and rendering dozens and even hundreds of millions of particles on any frame.

Note that the render output image size does NOT affect directly the rendering performance of Krakatoa when using Particle mode. Rendering 10 million particles (MP for Million Particles or MegaPoints) at 1K, 2K or 4K resolution will take about the same time (although the managing of larger image buffers could have a slight effect). But in order to produce the same high quality rendering at a higher resolution, more particles will be needed, thus indirectly affecting the render times.