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Setting Kernel Parameters

Some BlinkScript controls are used by all kernels. Rather than write these individually in each instance, the BlinkScript properties panel includes Kernel Parameters and Settings tabs, providing easy access to the standard kernel controls.

The Kernel Parameters tab also contains any controls exposed by specific kernel commands. For example, the default InvertKernel exposes the Multiply control. See Editing Kernels for more information on exposing controls.

The Publish button also resides on the Kernel Parameters tab, but we'll get into that in more detail in Publishing and Protecting Your Kernels.

GPU or CPU?

The read-only Local GPU field displays the graphics card installed locally, if there is one available. You can toggle the GPU on and off using the Use GPU if available control. If you have multiple GPUs available, select the required device using the Preferences > Performance > Hardware > default blink device dropdown.

Note:   Selecting a different GPU requires you to restart Nuke before the change takes effect.

Tip:  Even if there is no GPU available locally, you can still enable Use GPU if available. BlinkScript then uses the GPU as and when one becomes available.
You should also enable this if you wish to render from the command line with the --gpu option.

The output between the GPU and CPU is identical on NVIDIA GPUs, but using the GPU can significantly improve processing performance.

Note:  If your computer enters sleep mode, the CUDA drivers cannot recover and you must restart Nuke to use GPU acceleration.

Nuke supports AMD GPUs on late 2013 Mac Pro 6,1 and mid 2015 Mac Pro 11,5, running OS X 10.9.3 'Mavericks', or later. While, in some cases the bit-wise equality between GPU and CPU holds, for some operations there are limitations to the accuracy possible with this configuration.

Running Nuke on late 2013 Mac Pro 6,1 and mid 2015 Mac Pro 11,5, running OS X 10.9.3 'Mavericks', or later, adds an additional control allowing you enable multi-GPU processing. The option is global, applying to all GPU accelerated nodes, and is enabled in the Preferences > Performance > Hardware tab under GPU.

Note:  The multi-GPU preference is only displayed if you're using Nuke on late 2013 Mac Pro 6.1, running OS X 10.9.3 'Mavericks', or later. See Requirements for GPU Acceleration for more information on use.

Additionally, enable Vectorize on CPU to use SIMD acceleration on the CPU where possible. See Help > Documentation for more information on kernel execution.

Specifying the Output Format

BlinkScript's output defaults to the union of all its inputs, but you can specify a different output format by enabling Specify output format and selecting the required ratio from the format dropdown.

Tip:  Enabling Specify output format also adds the format control to the kernel once it has been published. See Publishing and Protecting Your Kernels for more information.

Changing Performance Settings

The performance controls on the Settings tab are common to all Blink kernels and don't affect the output, but can improve the processing speed:

• Percentage of GPU memory to use - sets the upper limit on the amount of memory BlinkScript can allocate.

Higher values than the default 50% can improve render times, but may introduce errors if the GPU is in use by other tasks.

• Percentage of image height per tile - processing is done in tiles, where each tile is the full width of the image. Adjusting the percentage of the image height processed in any one tile can affect performance.

Higher values generally improve performance, providing that there is enough GPU memory available for processing large tiles, whereas lower values produce faster feedback to the Viewer.