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This page provides information on the Particle Shader component.


Overview

 

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The Particle Shader component is intended to shade particles, such as Splash, Mist and Foam.

It has been optimized to render very fast in comparison to a traditional material shader, while still being capable of achieving a large variety of different effects, such as sparks, embers, sand, or even thin cigarette smoke.

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Typically, the Particle Shader is used to shade particles exported by the Phoenix Simulator. However, it can also shade non-Phoenix particle systems, in order to render particles from 3ds Max’s Particle Flow, tyFlow, and Thinking Particles.

Simply create a Particle Shader node, add a Phoenix particle system by picking the Phoenix Simulator (or any other external particle system that you wish to render), and the Particle Shader will shade it using the cache data from the sim. Since the Particle Shader is a separate node, you can use multiple Particle Shaders with different settings, in order to shade multiple particle systems within the same simulation.

The Particle Shader also provides several different shading modes for more sophisticated control, enabling you to quickly achieve a large variety of different effects for different scenarios. It can draw particles as Points, a variety of different Bubbles, or even voxelize particles into a grid using the Fog mode.

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These Particle Shader modes are designed with specific particle types in mind; for example, the Splashes mode is typically used to shade Splash particles.

However, Phoenix also offers the flexibility to use any mode to shade any particle type, so that you can create fine-tuned appearances for different particle types when rendering.

Note that there are three different bubble-style modes available that are intended for different scenarios: Bubbles, Cellular, and Splashes. Bubbles and Splashes are typically used for shading Foam and Splash particles respectively. Meanwhile, the Cellular mode renders polyhedron-like cells, that look very similar to real foam. Consequently, this mode can be used to shade Foam particles that are close-up to the camera, and have the results look convincing.

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Note that the Points mode shades particles as flat discs, and it renders faster than the Bubbles, Cellular, and Splashes modes. It can be useful for shading large scale foam and splashes over a large surface, such as an ocean surface, as well as for rendering non-foamy fluids, such as smoke or ink.

Meanwhile, the Fog mode voxelizes the content into a grid and uses the volumetric shader to render it. It can be a useful option for shading Mist particles, for example.

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For a list of supported Render Elements, please check the V-Ray Render Elements Support page.

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This rollout is accessible when Mode is set to Bubbles, Cellular, or Splashes.

Refractive Index | ri – The IOR of the bubble material. Higher refractive indices produce more pronounced reflection and refraction For more information, see the Ref. Refractive Index example below.

Bounces | bounces – Specifies the maximum depth of reflection/refraction branches. When the limit is reached, the color of the Environment texture will be used instead of starting new rays. Using more bounces slows down the rendering considerably, but reduces any flickering that may appear with a higher Refractive index.

Reflection Cut Off | minw – Starting a reflection ray is an expensive operation because it produces an avalanche of rays that can consume resources very quickly. Because of this, a reflection ray is only started if its result is very visible. This parameter is used to determine the critical visibility at which new reflection rays will start. If the visibility is less than the specified value, the Environment map will be used instead of tracing a new ray. This option has no effect if the Bounces are 0.

Highlights Width | hlwidth – Specifies the width of the specular highlights.

Highlights Strength | hlmult – Specifies a multiplier to control the brightness of the highlights. 

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When using complex lighting with many light sources or dome lights with HDRI maps, increasing the Light Cache Speedup option will cause the highlights to jitter over the surfaces of bubbles and this might cause flickering or noise in animation.

Pressure Variation | pvar – This parameter is used when Mode is set to Cellular, which produces a wall between each two bubbles in contact. In nature, no two bubbles in contact have exactly the same internal pressure, and the bubble with the higher pressure pushes against the lower-pressure bubble to produce a curved wall between the two. In the simulation, a random pressure difference is assigned to bubbles in contact, with the Pressure Variation value as the maximum. Larger values result in a more pronounced curve between the bubbles.

Optimize Congestion | optimize – When the particles overlap significantly in tight bunches such as beer head simulations, the render speed may drop significantly. With this option, an optimization pre-process is performed that deletes the bubbles that are fully inside other bubbles, and decreases the sizes of significantly overlapped bubbles. This reduces render times with a minimal impact on quality. Enabling this option is highly recommended.

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 If you get noise and flickering during animation rendering, try disabling Optimize Congestion as it will help bubbles to not disappear and re-appear in animation.

Reflection Coloring | usereflmap, reflmap – Used to represent the coloring of the bubble reflection due to interference. The texture is sampled using the direction instead of the explicit coordinates.

Environment | useenvmap, envmap – This map is used when the visibility is less than the Reflection Cut Off value, or when the renderer's reflection depth is reached. For example, when using V-Ray's VRayMtl, reflection depth is determined by the Cutoff and Reflection Max Depth parameters. The texture is sampled using the direction instead of the explicit coordinates.

Glass Geometry | useglass, glass – Used to introduce some corrections in the way bubbles interact with glass. Note that the bubbles should touch the glass geometry, otherwise this option has no effect.. For more information, see the Glass Geometry example below.

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Example:

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Refractive Index

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The image below shows the render differences between Refractive index values of 1.2, 1.6, and 3.0.

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