Nvidia Flow TOP

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Summary
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NVIDIA Flow is a volumetric fluid based simulation of a burning gas system. The user controls the 3 main factors of temperature, fuel, and smoke to create fire and smoke simulations.

The Nvidia Flow TOP calculates the Flow simulation and renders it. It requires a Nvidia Flow Emitter COMP to emit gas into the Flow simulation. This operator only works with Nvidia GPUs.

See also Nvidia Flow Emitter COMP, Nvidia Flow.

Read more here Nvidia Flow Artist Tools

PythonIcon.pngflowTOP_Class


Parameters - Setup Page

Initialize initialize - Initializes the simulation.  

Start start - Starts the simulation playback.  

Play play - The simulation only steps forward when Play = On, when off the simulation is paused.  

Camera camera - Specify the Camera COMP to view the simulation from. Note: Must be camera with Projection = Perspective.  

Flow Emitters emitters - Specify the Nvidia Flow Emitter COMPs to include in the simulation.  

Sim Position simposition - - The position of the simulation volume's center, in the world. The simulation cannot extend outside of the volume.

  • X simpositionx -
  • Y simpositiony -
  • Z simpositionz -

Sim Size simsize - - The size of the simulation volume in the world. The simulation cannot extend outside of the volume. Also controls the size of simulation blocks, so the total number of blocks in the volume stays the same. Smaller size blocks will require more blocks for the same size simulation. This increases accuracy but makes the simulation more taxing on the GPU as there are more blocks to calculate.

  • X simsizex -
  • Y simsizey -
  • Z simsizez -

Mem Usage memusage - Controls relative memory usage, the fraction of the total simulation blocks that will be allocated. Most simulations will not fill the simulation volume uniformly, so only a small value is needed. High values will cause extremely high memory usage.  

Show Blocks showblocks - Displays the simulation blocks being used. Useful for debugging or optimizing your Flow simulation. Also shows the edges of the simulation volume.  

Show Emit Bounds showemitbounds - Displays the bounds of the emitters.  

Show Shapes showshapes - Displays the shapes of the emitters.  

Speed speed - Controls the update rate of the simulation.  

Max Simulation Steps maxsteps - Maximum number of simulation steps per update. A higher number of steps will increase quality for fast moving object at the cost of performance.  


Parameters - Settings Page

Gravity gravity - - Gravity direction for use with Buoyancy parameter, where amount controls strength of buoyancy force.

  • X gravityx -
  • Y gravityy -
  • Z gravityz -

Velocity Damping veldamping - Higher values reduce velocity faster. Uses exponential decay curve.  

Velocity Fade velfade - Compared to damping, fade reduces low velocity values faster. Fade velocity rate is in units per second.  

Smoke Damping smokedamping - Higher values reduce smoke faster. Uses exponential decay curve.  

Smoke Fade smokefade - Compared to damping, fade reduces low smoke values faster. Fade velocity rate is in units per second.  

Temp Damping tempdamping - Higher values reduce temperature faster. Uses exponential decay curve.  

Temp Fade tempfade - Compared to damping, fade reduces low temperature values faster. Fade velocity rate is in units per second.  

Fuel Damping fueldamping - Higher values reduce fuel faster. Uses exponential decay curve.  

Fuel Fade fuelfade - Compared to damping, fade reduces low fuel values faster. Fade velocity rate is in units per second.  

Vorticity Strength vortstrength - Controls amount of rotation turbulence as a multiplier, a value of 0 will result in no vorticity. High values increase turbulent flow while low values increase laminar flow.  

Vorticity from Velocity vortfromvel - Amount of vorticity added from velocity.  

Vorticity from Smoke vortfromsmoke - Amount of vorticity added from smoke.  

Vorticity from Temp vortfromtemp - Amount of vorticity added from temperature.  

Vorticity from Fuel vortfromfuel - Amount of vorticity added from fuel.  

Vorticity Constant vortconstant - The baseline vorticity in the simulation.  

Ignition Temp ignitiontemp - Specify the minimum temperature required for combustion.  

Burn per Temp burnpertemp - Control how much fuel is burned for a given temperature level. Lower Burn per Temp may result in some fuel not burning completely at a certain temperature.  

Smoke per Burn smokeperburn - Controls amount of smoke generated for each unit of combustion (per burn).  

Temp per Burn tempperburn - Controls amount of temperature generated for each unit of combustion (per burn).  

Fuel per Burn fuelperburn - Controls amount of fuel used for each unit of combustion (per burn).  

Buoyancy buoyancy - Works in conjunction with the parameter Gravity above which sets a vector for use by Buoyancy. Higher values result in greater effect by the Gravity parameter.  

Cooling Rate coolingrate - The rate of cooling in the system, exponential.  

Expansion expansion - Controls the amount the system's gaseous volume expands.  


Parameters - Volume Shadow Page

Enable enableshadow - Enables Volume shadow rendering for the simulation. Shadowing generates light intensity values that overwrite the "burn" channel of the grid. Values range from 0 to 1, where 0 is fully shadowed. Shadow visibilty can be controlled by enabling 'Override Emitter Intensity Mask' or by adjusting the 'Burn Intensity Mask', 'Burn Alpha Mask', and 'Burn Color Mask' in Nvidia Flow Emitter COMP  

Draw Debug drawshadowdebug - Displays the volume shadow blocks being used. Useful for debugging or optimizing.  

Override Emitter Intensity Mask overrideemitter - Automatically adjusts the emitters' render material, so volume shadows are visible. Will override 'Burn Intensity Mask' and 'Intensity Bias' of emitters.  

Light light - The light source used to generate volume shadow. The light should be a shadow caster. Only the position and orientation of the light are used, color and intensity are ignored.  

Shadow Resolution shadowresolution - The resolution of the shadow map volume texture. The texture is allocated as a cube, so there will be space for shadowresolution^3 blocks.  

Min Memory Usage shadowminusage - The initial fraction of volume shadow blocks to allocate memory for.  

Max Memory Usage shadowmaxusage - The maximum fraction of volume shadow blocks to allocate memory for.  

Intensity Scale shadowintensityscale - Scales how dark the shadow will be.  

Min Intensity shadowminintensity - A lower limit for shadow intensity.  

Burn Blend Mask shadowburnmask - Allows the burn value in the simulation to control the blend strength of the shadow. Postive values mean burn increases the blend strength, negative values mean burn decreases the blend strength  

Smoke Blend Mask shadowsmokemask - Allows the smoke value in the simulation to control the blend strength of the shadow. Postive values mean smoke increases the blend strength, negative values mean smoke decreases the blend strength  

Temp Blend Mask shadowtempmask - Allows the temperature value in the simulation to control the blend strength of the shadow. Postive values mean temp increases the blend strength, negative values mean temp decreases the blend strength  

Fuel Blend Mask shadowfuelmask - Allows the fuel value in the simulation to control the blend strength of the shadow. Postive values mean fuel increases the blend strength, negative values mean fuel decreases the blend strength  

Blend Bias shadowblendbias - An offset that increases or decreases the blend strength by a constant amount. Parts of the grid with a blend value over 1 will have shadows. Parts of the grid with blend value under 1 will not have shadows. Blend values between 0 and 1 scale the strength of shadow.  


Parameters - Common Page

Output Resolution outputresolution - - quickly change the resolution of the TOP's data.

  • Use Input useinput - Uses the input's resolution.
  • Eighth eighth - Multiply the input's resolution by that amount.
  • Quarter quarter - Multiply the input's resolution by that amount.
  • Half half - Multiply the input's resolution by that amount.
  • 2X 2x - Multiply the input's resolution by that amount.
  • 4X 4x - Multiply the input's resolution by that amount.
  • 8X 8x - Multiply the input's resolution by that amount.
  • Fit Resolution fit - Grow or shrink the input resolution to fit this resolution, while keeping the aspect ratio the same.
  • Limit Resolution limit - Limit the input resolution to be not larger than this resolution, while keeping the aspect ratio the same.
  • Custom Resolution custom - Directly control the width and height.

Resolution resolution - - Enabled only when the Resolution parameter is set to Custom Resolution. Some Generators like Constant and Ramp do not use inputs and only use this field to determine their size. The drop down menu on the right provides some commonly used resolutions.

  • W resolutionw -
  • H resolutionh -

Resolution Menu resmenu - A drop-down menu with some commonly used resolutions.  

Use Global Res Multiplier resmult - Uses the Global Resolution Multiplier found in Edit>Preferences>TOPs. This multiplies all the TOPs resolutions by the set amount. This is handy when working on computers with different hardware specifications. If a project is designed on a desktop workstation with lots of graphics memory, a user on a laptop with only 64MB VRAM can set the Global Resolution Multiplier to a value of half or quarter so it runs at an acceptable speed. By checking this checkbox on, this TOP is affected by the global multiplier.  

Output Aspect outputaspect - - Sets the image aspect ratio allowing any textures to be viewed in any size. Watch for unexpected results when compositing TOPs with different aspect ratios. (You can define images with non-square pixels using xres, yres, aspectx, aspecty where xres/yres != aspectx/aspecty.)

  • Use Input useinput - Uses the input's aspect ratio.
  • Resolution resolution - Uses the aspect of the image's defined resolution (ie 512x256 would be 2:1), whereby each pixel is square.
  • Custom Aspect custom - Lets you explicitly define a custom aspect ratio in the Aspect parameter below.

Aspect aspect - - Use when Output Aspect parameter is set to Custom Aspect.

  • Aspect1 aspect1 -
  • Aspect2 aspect2 -

Aspect Menu armenu - A drop-down menu with some commonly used aspect ratios.  

Input Smoothness inputfiltertype - - This controls pixel filtering on the input image of the TOP.

  • Nearest Pixel nearest - Uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
  • Interpolate Pixels linear - Uses linear filtering between pixels. This is how you get TOP images in viewers to look good at various zoom levels, especially useful when using any Fill Viewer setting other than Native Resolution.
  • Mipmap Pixels mipmap - Uses mipmap filtering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail.

Fill Viewer fillmode - - Determine how the TOP image is displayed in the viewer. NOTE:To get an understanding of how TOPs work with images, you will want to set this to Native Resolution as you lay down TOPs when starting out. This will let you see what is actually happening without any automatic viewer resizing.

  • Use Input useinput - Uses the same Fill Viewer settings as it's input.
  • Fill fill - Stretches the image to fit the edges of the viewer.
  • Fit Horizontal width - Stretches image to fit viewer horizontally.
  • Fit Vertical height - Stretches image to fit viewer vertically.
  • Fit Best best - Stretches or squashes image so no part of image is cropped.
  • Fit Outside outside - Stretches or squashes image so image fills viewer while constraining it's proportions. This often leads to part of image getting cropped by viewer.
  • Native Resolution nativeres - Displays the native resolution of the image in the viewer.

Viewer Smoothness filtertype - - This controls pixel filtering in the viewers.

  • Nearest Pixel nearest - Uses nearest pixel or accurate image representation. Images will look jaggy when viewing at any zoom level other than Native Resolution.
  • Interpolate Pixels linear - Uses linear filtering between pixels. Use this to get TOP images in viewers to look good at various zoom levels, especially useful when using any Fill Viewer setting other than Native Resolution.
  • Mipmap Pixels mipmap - Uses mipmap filtering when scaling images. This can be used to reduce artifacts and sparkling in moving/scaling images that have lots of detail. When the input is 32-bit float format, only nearest filtering will be used (regardless of what is selected).

Passes npasses - Duplicates the operation of the TOP the specified number of times. For every pass after the first it takes the result of the previous pass and replaces the node's first input with the result of the previous pass. One exception to this is the GLSL TOP when using compute shaders, where the input will continue to be the connected TOP's image.  

Channel Mask chanmask - Allows you to choose which channels (R, G, B, or A) the TOP will operate on. All channels are selected by default.  

Pixel Format format - - Format used to store data for each channel in the image (ie. R, G, B, and A). Refer to Pixel Formats for more information.

  • Use Input useinput - Uses the input's pixel format.
  • 8-bit fixed (RGBA) rgba8fixed - Uses 8-bit integer values for each channel.
  • sRGB 8-bit fixed (RGBA) srgba8fixed - Uses 8-bit integer values for each channel and stores color in sRGB colorspace. Note that this does not apply an sRGB curve to the pixel values, it only stores them using an sRGB curve. This means more data is used for the darker values and less for the brighter values. When the values are read downstream they will be converted back to linear. For more information refer to sRGB.
  • 16-bit float (RGBA) rgba16float - Uses 16-bits per color channel, 64-bits per pixel.
  • 32-bit float (RGBA) rgba32float - Uses 32-bits per color channel, 128-bits per pixels.
  • 10-bit RGB, 2-bit Alpha, fixed (RGBA) rgb10a2fixed - Uses 10-bits per color channel and 2-bits for alpha, 32-bits total per pixel.
  • 16-bit fixed (RGBA) rgba16fixed - Uses 16-bits per color channel, 64-bits total per pixel.
  • 11-bit float (RGB), Positive Values Only rgba11float - A RGB floating point format that has 11 bits for the Red and Green channels, and 10-bits for the Blue Channel, 32-bits total per pixel (therefore the same memory usage as 8-bit RGBA). The Alpha channel in this format will always be 1. Values can go above one, but can't be negative. ie. the range is [0, infinite).
  • 16-bit float (RGB) rgb16float -
  • 32-bit float (RGB) rgb32float -
  • 8-bit fixed (Mono) mono8fixed - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 8-bits per pixel.
  • 16-bit fixed (Mono) mono16fixed - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
  • 16-bit float (Mono) mono16float - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 16-bits per pixel.
  • 32-bit float (Mono) mono32float - Single channel, where RGB will all have the same value, and Alpha will be 1.0. 32-bits per pixel.
  • 8-bit fixed (RG) rg8fixed - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 8-bits per channel, 16-bits total per pixel.
  • 16-bit fixed (RG) rg16fixed - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 16-bits per channel, 32-bits total per pixel.
  • 16-bit float (RG) rg16float - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 16-bits per channel, 32-bits total per pixel.
  • 32-bit float (RG) rg32float - A 2 channel format, R and G have values, while B is 0 always and Alpha is 1.0. 32-bits per channel, 64-bits total per pixel.
  • 8-bit fixed (A) a8fixed - An Alpha only format that has 8-bits per channel, 8-bits per pixel.
  • 16-bit fixed (A) a16fixed - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
  • 16-bit float (A) a16float - An Alpha only format that has 16-bits per channel, 16-bits per pixel.
  • 32-bit float (A) a32float - An Alpha only format that has 32-bits per channel, 32-bits per pixel.
  • 8-bit fixed (Mono+Alpha) monoalpha8fixed - A 2 channel format, one value for RGB and one value for Alpha. 8-bits per channel, 16-bits per pixel.
  • 16-bit fixed (Mono+Alpha) monoalpha16fixed - A 2 channel format, one value for RGB and one value for Alpha. 16-bits per channel, 32-bits per pixel.
  • 16-bit float (Mono+Alpha) monoalpha16float - A 2 channel format, one value for RGB and one value for Alpha. 16-bits per channel, 32-bits per pixel.
  • 32-bit float (Mono+Alpha) monoalpha32float - A 2 channel format, one value for RGB and one value for Alpha. 32-bits per channel, 64-bits per pixel.


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An Operator Family that creates, composites and modifies images, and reads/writes images and movies to/from files and the network. TOPs run on the graphics card's GPU.

The Graphics Processing Unit. This is the high-speed, many-core processor of the graphics card/chip that takes geometry, images and data from the CPU and creates images and processed data.

The width and height of an image in pixels. Most TOPs, like the Movie File In TOP can set the image resolution. See Aspect Ratio for the width/height ratio of an image, taking into account non-square pixels.

The viewer of a node can be (1) the interior of a node (the Node Viewer), (2) a floating window (RMB->View... on node), or (3) a Pane that graphically shows the results of an operator.

A CHOP outputs one or more channels, where a channel is simply a sequence of numbers, representing motion, audio, etc. Channels are passed between CHOPs in TouchDesigner networks. See also Export.