The Phoenix Particle Type is designed to shade particles, such as Splash, Mist and Foam. Phoenix particles are 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.

Render Mode – Specifies how to render the particles - as Volumetric or Geometry objects.

Volumetric – When set to Volumetric mode, the particles are rendered as a volumetric atmosphere effect, which is faster, and is suitable for most cases.
Geometry – When set to Geometry mode, the particles are rendered as procedural geometry with multiple transparency layers. We recommend using this mode only in cases, where Volumetric is not suitable.

Mode – Sets the shading mode. Depending on the mode, there are different options available in the section below.

Bubbles – Each particle is shaded as a spherical, transparent, reflective foam bubble. Surfaces of bubbles that intersect one another are visible inside the bubbles. If you get flickering or noisy renders of tightly packed masses of foam such as beer heads, switch to Cellular mode. Otherwise, in animation, pairs of bubbles would appear with one bubble completely in front of another in one frame, and completely behind on the next frame, once the bubble's center goes behind the other bubble's center. This would cause abrupt changes in the overall look of the foam mass in animation.

Cellular – Similar to Bubbles mode, but replaces intersecting walls between bubbles with a curved wall. The degree of curvature is determined by the Pressure Variation parameter. This mode is about twice as slow as simple Bubbles but is suitable for close-up foam.

Splashes – Each particle is shaded as a spherical, opaque, reflective droplet. Surfaces of droplets that intersect one another are not visible.

Points – Particles are shaded as flat discs, each the size of one pixel by default. This mode is faster than Bubbles, Cellular, and Splashes and thus is suitable for large scale foam and splashes over a large surface, such as an ocean surface. This mode is also suitable for rendering non-foamy fluids such as smoke or ink. Because the points are pixel sized, moving the camera away or decreasing the render resolution makes them appear denser, while moving the camera in closer or increasing the render resolution make the particles look more scattered. Note that Point mode does not do reflections or refractions like the Bubbles, Cellular, and Splashes, so the particles look diffuse and sometimes darker if you render them next to strongly reflective materials.

Fog – Each particle is put into a grid and the smoke shader is used to visualize the grid's content. This mode is an alternative to Points mode.

Color Source – Specifies how the color of the particles is determined.

Color – Specifies the particle color.
Texture – See the Color Source: Texture section.
Particle Channel – See the Color Source: Particles Channel section.

Color Source: Texture – Allows you to connect a texture to drive the color of the particles.

Color Map – Specifies the particle color, if there is no texture attached.

Texture – Specifies the texture map used as the particle color.

Mix Strength – Specifies the blend amount between the Color Map and the Texture. If set to 100%, only the Texture is visible.

Mix Type – Specifies how the two are blended together.

Normal
Add
Subtract
Multiply

Color Source: Particles Channel – Allows you to connect a particle channel to shade the particles.

Particle Channel – Specifies the particle channel to be used.

Diffuse Multiplier – Provides an additional option to multiply the color brightness.

Size Multiplier – Acts as an additional parameter for controlling the bubbles/splashes size, independent of their particle system. This parameter can be animated to reduce the size of the rendered particles over time. If the Size Multiplier by Age option is enabled, the animation is applied on a per-particle basis rather than acting simultaneously over the entire particle group. The value for this parameter is not set as a constant but instead is affected by the Size Variation and Size Distribution parameters. This introduces randomness in a particle system where all particles have the same size.

Size Multiplier by Age – When enabled, animation of the Size Multiplier parameter is evaluated individually for each particle. The Age channel of individual particles is treated as if it is the Timeline itself, and animation applied to the Size Multiplier is evaluated over it. Therefore, the Size Multiplier animation is applied to each particle, starting at its time of birth. For example, animating the Size Multiplier to go from 1 to 0 over Timeline frames 0 to 30 will individually scale down each particle during the first 30 frames of its birth. Conversely, when this option is disabled, the Size Multiplier animation treats the particles as a collection of points, and scales them simultaneously, regardless of their current age. For example, animating the Size Multiplier to go from 1 to 0 over Timeline frames 0 to 30 simultaneously scales all particles in the simulation over the first 30 Timeline frames, and none is visible on frame 31.

Size Addend – Add this to the size of the particles in order to make them larger, or smaller if a negative value is used. Unlike Size Multiplier which would scale all particles proportionally, Size Addend adds a fixed number to all particle sizes. If both Size Multiplier and Size Addend are used, the Size Multiplier scales the sizes first, and then the Size Addend is added.

Size Distribution – Controls the number of bubbles that change size as a result of the Size Multiplier. When this value is set to 0, all particle sizes are multiplied by the Size Multiplier. When this value is greater than 0, some particles are multiplied by a higher value, and some are multiplied by a lower value. Setting this value to 1 ensures that an equal amount of particles are made larger as those that remain smaller. Increasing this parameter produces many smaller particles and fewer big particles.

Size Variation – Adds randomization to the Size Multiplier so that different particles are scaled differently. The higher the variation, the larger the difference between the smaller and the larger particles.

Particle Count Multiplier – Increases or decreases the number of particles for rendering. When the value is below 1, the particle count decreases, skipping the particles randomly. When the value is above 1, new particles are created and placed randomly among the original ones in a way that attempts to preserve the group's overall shape. Note that you have to export the particle ID channel if you want to render animation, otherwise the particles would start appearing and disappearing in different places during the animation.

Scattering Method – Controls how the light rays are scattered inside the particle volume.

Ray-traced – Enables physically accurate scattering of light rays. This mode produces the most realistic results but it's the slowest to render. It requires V-Ray with enabled Global Illumination, otherwise the rendered result would be the same as if the option is Disabled. The Diffuse Multiplier does not affect the rendering in this mode.

Disabled – Disables scattering. The Diffuse Multiplier value can be used to correct the brightness because without light scattering the particles would generally render darker.

Approximate – Uses an approximate formula which is faster than Ray-traced scattering and produces good looking results. This option is not supported when the Render Mode is set to Geometry.

Approximate+Shadows – Same as Approximate, but also affects the strength of shadows over the scene geometry. This option is not supported when the Render Mode is set to Geometry.

Motion Blur – Controls the motion blur effect.

From Renderer – The current renderer's own motion blur setting is used.
Force On – The content is rendered with motion blur regardless of the global setting.
Force Off – The content is rendered without motion blur regardless of the global setting.

Velocity Multiplier – Can be used to make the motion blur effect stronger or weaker. This value can also be negative and would change the motion blur direction.

Volume Light Cache – Enables light caching, which can speed up bucket rendering considerably. When using V-Ray Progressive Rendering, the Volume Light Cache option might slow down rendering startup or the overall render speed. This option refers to the Phoenix FD Light Cache, which is unrelated to the V-Ray Light Cache.

Light Cache Speedup – This option is only available when Volume Light Cache is enabled. Reduces the quality of the Volume Light Cache and increases the rendering speed. You can increase this and gain render speed as long as you don't start getting artifacts and excessive flickering in animation. Note that when using complex lighting with many light sources or Dome lights with HDRI maps, combined with Bubbles, Cellular or Splashes mode, increasing this option will cause the highlights to jitter over the surfaces of bubbles and this might cause flickering or noise in animation.

Material ID – Determines the color for the Material ID Render Element when the Render Mode is set to Volumetric.

Points

Ignore Particle Size – By default, V-Ray Particles calculates the alpha by considering the size of the particle and the distance to it. This option is used when the particle system contains particles that are too large and leave hard tracks with motion blur.

Point Radius (pixels) – Specifies a multiplier for the size of the point disc. By default, points are the size of one pixel. Increasing the point size speeds up rendering.

Point Opacity – Specifies a multiplier for the opacity of all the points.

Shadow Strength – Specifies a multiplier for the shadow strength. Increasing this value creates darker shadows but slows down rendering.

Motion Blur Step – Unlike the Bubbles, Cellular, and Splashes modes, motion blur in Points mode is calculated by cloning the particle several times and placing the copies along the trajectory. This parameter controls the distance between the copies. The smaller the step, the higher the quality, though at the cost of render time.

Motion Blur Limit – The maximum number of particles per motion blurred streak. If the particle system contains very fast particles, or if the motion blur step is too small, there is a possibility of rendering overload, due to a huge number of particle copies. This parameter sets a limit on the number of clones to keep render times reasonable.

Bubbles/Cellular/Splashes

Refractive Index – The IOR of the bubble material. Higher refractive indices produce more pronounced reflection and refraction.

Bounces – Specifies the maximum depth of reflection/refraction branches. Using more bounces slows down the rendering considerably, but reduces any flickering that may appear with a higher Refractive Index.

Reflection Cut Off – Starting a reflection ray is an expensive operation. 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, no ray is traced. This option has no effect if the Bounces are 0.

Highlight Width – Specifies the width of the specular highlights.

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

Pressure Variation – 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.

Optimized Congestion – 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.

Fog

Fog Voxel Size – Specifies the cell size of the smoke grid.

Fog Density – Specifies a multiplier for the fog density.