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This node cooks a ROP node or network using TOPs in either the current .hip file or an external file. It creates one work item per frame, based on the frame generation parameters.
Optionally, you can batch the work items into a single job for all frames, or divide them into smaller groups of frames. This node cooks each batch as a single job on the farm or locally. Batching all frames into one job is typically used for simulations so that the simulation data can be kept in memory rather than be cached to disk. Smaller batch sizes, like a 4-frames-per job, can also help avoid overhead loading the .hip file when cooking a ROP that cooks quickly.
Tip
Often a custom driver node will write out several files which will not be automatically picked up by PDG as output files. However, if the driver node has a toggle parameter named pdg_logoutput that parameter will be toggled to true before it is cooked by the Rop Fetch, and the printed output will be parsed for lines which match the pattern OUTPUT_FILE:{file_path};. Each matched file_path will become output files for the Rop Fetch work item.
TOP Attributes
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string |
The path to the |
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string |
The name of the parameter on the target ROP node that contains the output
file path. For example, when used with a ROP Geometry node, this attribute
will be set to |
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string |
The ROP node path within the |
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string |
If the ROP is contained within a TOP asset, such as the ROP Geometry node, then this attribute is set to the path to that TOP node. |
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string |
If the Source Node Path is set, then this attribute contains the path to the source data used by the ROP this work item is cooking. |
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string |
When running a distributed sim, this attribute is set to the path to the Control DOP node. |
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string |
When running a distributed sim, this attribute is set to the identifier for the shared sim tracker process. |
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string |
When running a distributed sim, this attribute is set to the hostname of the machine that has the distributed sim tracker. |
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integer |
When running a distributed sim, this attribute is set to the port used to
connect to the sim tracker. In combination with |
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float3 |
The start, end, and increment frame range values associated with the work item. If the work item is in a batch, then these values refer to the range for the entire batch. |
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integer |
When running a distributed sim, this attribute is set to the slice number associated with the work item. |
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integer |
The type of distributed sim being used, set to either |
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integer3 |
When using volume slices, this attribute is set to the x, y, and z slice divisions. |
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integer |
When using the ROP Fetch node to cook a tiled Mantra render, this value is set to the render tile index associated with the work item. |
Parameters
ROP Fetch
Work Item Generation
Whether this node generates static or dynamic work items. You should generally leave this set to "Automatic" unless you know the node’s work items can be computed statically, or that they need to be generated dynamically.
Dynamic
This node always creates dynamic work items: it waits until the upstream work items are known, and generates new work items from the upstream work items.
Static
This node always creates static work items: it creates the number of work items it thinks it needs based on the parameters (and any upstream static items) before the network runs.
Automatic
If the input is static (a static processor, or a partitioner with only static inputs, or a mapper), this node generates static work items, otherwise it generates dynamic work items.
Cache Mode
How the processor node handles work items that report expected file results.
Automatic
If the expected result file exists on disk, the work item is marked as cooked without being scheduled. If the file does not exist, the item is scheduled as normal.
Read Files
If the expected result file exists on disk, the work item is marked as cooked without being scheduled. Otherwise the work item is marked as failed.
Write Files
Work items are always scheduled and the excepted result file is ignored, even if it exists on disk.
ROP Path
The path to the ROP node or network that is cooked by this TOP node.
Output File Tag
When on, specifies a custom file tag.
By default, the ROP Fetch node tags output files based on their file extensions. You can use this parameter to override that behavior.
Output Parm Name
When on, specifies the name of the output file parameter on the target ROP node.
By default, for standard ROP nodes shipped with Houdini, PDG is able to automatically determine the output name based on the type of ROP. When using a custom ROP or a ROP that PDG fails to detect automatically, this parameter should be set to the string name of the output parameter on the ROP specified in the ROP Path field.
Source Node Path
When on, specifies the path to the underlying node or network that the ROP Path will use when the ROP evaluates. This creates a dependency between that node and this TOP node, so that this TOP node is correctly marked as dirty when the source node changes.
For example, if you're using this ROP Fetch node to cook a Geometry ROP, then you would set the value of this parameter to the SOP network associated with your Geometry ROP.
If this parameter is not set then no dependency will be created. Likewise, if External HIP File is enabled this parameter will also not be used, since the ROP being cooked is in a different .hip file.
External HIP File
When on, specifies the path to the .hip file that contains the ROP node.
This is most commonly used when generating a .hip file procedurally as part of an earlier step in the TOP network.
When selecting a ROP in the current file, it is not necessary to specify this parameter.
Reset $HIP On Cook
When on, sets the $HIP variable in the job to the value of the $HIP on the submitting machine.
This is most commonly used to keep all the $HIP-based file references in the file valid when copying the .hip file to the staging directory.
Evaluate Using
Determines how the TOP node creates work items and executes. When using Single Frame the node will create one work item for each upstream frame. When using Frame Range the node creates one work item per frame in the range, for each upstream work item.
Single Frame
The node will create a single work item per upstream item, and will set the new work item’s frame to match the upstream item’s frame. If there are no input nodes then a single item set to frame 1 will be created. The single frame value can be overridden using the Override Frame parameter.
Frame Range
For each upstream work item, the node will create the full frame range of work items. If there are no upstream items, the node will create one set of items for the specified frame range.
Override Frame
When this parameter is enabled, it overrides the frame used with the Single Frame Evaluation mode.
Frame Range
The frame start, end and step size to use when Frame Generation is set to Frame Range.
Cook Frames as Single Work Item
This parameter is only available when Evaluating Using is set to Frame Range.
Groups the work for all frames into a single work item.
This is most commonly used when cooking a ROP that produces an FBX, Alembic, or USD file which contains multiple frames of data in the same file.
Expand Input Files Across Frame Range
This parameter is only available when Evaluating Using is set to Frame Range.
Spreads the input file list across the frame range.
For example, if the upstream work item has 100 output files and the frame range on this node is set to 1 to 50, then each work item in this node will have 2 input files. The first work item will have file 1 and file 2, the second work item will have file 3 and file 4, and so on.
All Frames in One Batch
When this toggle is enabled, work items from the same frame range are grouped into a batch that is scheduled as a single job. This is used for simulations where each frame depends on the previous frame, and it is advantageous to keep everything in memory.
Frames per Batch
By default, when this parameter is at 1 each work item is cooked as a separate job. When this parameter is set to a value greater than 1, work items are grouped into batches.
Cook Batch When
Determines when batches of frames are scheduled.
By default, the batch is scheduled once the dependencies for all frames are cooked. However, it is possible to schedule the batch as soon as its first frame can run.
All Frames are Ready
The batch is scheduled only when all dependencies on all frames in the batch are satisfied.
First Frame is Ready
The batch is scheduled as soon as its first frame is ready.
This is possible because the ROP wrapper script used by PDG ensures that subsequent frames correctly wait for their dependencies. This is done by communicating back to PDG as the job is running to check the status of the dependencies before each frame. This incurs slightly more network overhead, and requires ongoing communication between the job and PDG.
This option is not available when cooking a 
Composite ROP node since COP file nodes must be able to load their entire input file sequence on the first frame.
Resume Partially Cached Batches
Determines whether or not batches produced by this node should resume cooking from partially cached output files. You should only enable this option for simulations if the DOP netwoprk itself is already configured to write sim cache files.
Distribution
Distributed Sim
When on, the node treats the target ROP as part of a distributed simulation. This enables the parameters for configuring a distributed sim, and disables the frame generation parameters.
Control DOP
The control DOP for the distributed sim.
Slice Type
The type of slicing used for the distributed sim.
Particles
Use the particle slicing method for the distributed sim.
Volumes
Use the volume slicing method for the distributed sim.
Slice Count
This parameter setting is only available when Slice Type is set to Particles.
Specifies the number of slices for the distributed sim.
Slice Divisions
This parameter setting is only available when Slice Type is set to Volumes.
Determines the x, y, and z volume divisions for the distributed sim.
Schedulers
TOP Scheduler Override
This parameter overrides the TOP scheduler for this node.
Work Item Priority
This parameter determines how the current scheduler prioritizes the work items in this node.
Inherit From Upstream Item
The work items inherit their priority from their parent items. If a work item has no parent, its priority is set to 0.
Custom Expression
The work item priority is set to the value of Priority Expression.
Node Defines Priority
The work item priority is set based on the node’s own internal priority calculations.
This option is only available on the 
Python Processor TOP, 
ROP Fetch TOP, and ROP Output TOP nodes. These nodes define their own prioritization schemes that are implemented in their node logic.
Priority Expression
This parameter is only available when Work Item Priority is set to Custom Expression.
This parameter specifies an expression for work item priority. The expression is evaluated for each work item in the node.
External Files
File Dependencies
A list of files that should be copied to the PDG working directory before the first work item in this node is executed. This can be used to ensure that supporting files like digital assets and custom scripts are available for the work item job.
The specified paths can be absolute or relative to HOUDINI_PATH.
Examples
example_top_ropfetch Example for ROP Fetch TOP node
This example demonstrates how to use the ROP Fetch node in PDG/TOPs.
| See also |
HDA Processor
