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The ROP Output DOP is usually used to mark the end of a DOP simulation chain. It should normally always have the Output flag set on itself.
It also provides the capabilities of the Dynamics ROP.
Output from this node can be played back using DOP Network Playback
Save to Disk
Saves the simulation to disk as a sequence of .sim files.
Save to Disk in Background
Starts another copy of Houdini in the background and instructs that copy to save out the simulation as a sequence of .sim files. This allows one to continue working and load the .sim files as they complete.
Specifies the range of frames to render (start frame, end frame, and increment). All values may be floating point values. The range is inclusive.
These parameters determine the values of the local variables for the output driver.
The number of frames to be rendered by the output driver.
The current frame being rendered (starting at 1 and going to
Render with Take
Uses the settings in a particular take while rendering. Choose Current to use the current take when rendering.
The file to save the simulation state to. Make sure to include $SF in the filename to write out separate files for each frame.
Output Every Sim Frame Using $SF
Every single simulation frame will be output, rather than just the frames hit by the step rate of the frame range. In this mode one just has to set the entire range without worrying about how sub-stepping will be set up.
$SF should be used instead of
$F in the file name in these
Initialize Simulation OPs
Force all simulation OPs to be reset. This includes DOP Networks, POP SOPs, and other OPs that cache their results.
This is the safest way to render out a simulation, because it starts the simulation from scratch and discards any partial simulations you might have done with different parameters. However, throwing away an already-cooked simulation can be expensive, especially for relatively slow solvers such as fluids.
Alfred Style Progress
A percentage complete value is printed out as files are written. This is in the style expected by Pixar’s Alfred render queue.
All the objects connected to the input of this node are fed out through the single output.
All the objects or data connected to the input of this node are fed out through the single output.
This value is the simulation time for which the node is being evaluated.
This value may not be equal to the current Houdini time represented by the variable T, depending on the settings of the DOP Network Offset Time and Time Scale parameters.
This value is guaranteed to have a value of zero at the
start of a simulation, so when testing for the first timestep of a
simulation, it is best to use a test like
$ST == 0 rather than
$T == 0 or
$FF == 1.
This value is the simulation frame (or more accurately, the simulation time step number) for which the node is being evaluated.
This value may not be equal to the current Houdini frame number represented by the variable F, depending on the settings of the DOP Network parameters. Instead, this value is equal to the simulation time (ST) divided by the simulation timestep size (TIMESTEP).
This value is the size of a simulation timestep. This value is useful to scale values that are expressed in units per second, but are applied on each timestep.
This value is the inverse of the TIMESTEP value. It is the number of timesteps per second of simulation time.
This is the number of objects in the simulation. For nodes that create objects such as the Empty Object node, this value will increase for each object that is evaluated.
A good way to guarantee unique object names is to use an expression
This value is the number of objects that will be evaluated by the current node during this timestep. This value will often be different from SNOBJ, as many nodes do not process all the objects in a simulation.
This value may return 0 if the node does not process each object sequentially (such as the Group DOP).
This value is the index of the specific object being processed by the node. This value will always run from zero to NOBJ-1 in a given timestep. This value does not identify the current object within the simulation like OBJID or OBJNAME, just the object’s position in the current order of processing.
This value is useful for generating a random number for each object, or simply splitting the objects into two or more groups to be processed in different ways. This value will be -1 if the node does not process objects sequentially (such as the Group DOP).
This is the unique object identifier for the object being processed. Every object is assigned an integer value that is unique among all objects in the simulation for all time. Even if an object is deleted, its identifier is never reused.
The object identifier can always be used to uniquely identify a given object. This makes this variable very useful in situations where each object needs to be treated differently. It can be used to produce a unique random number for each object, for example.
This value is also the best way to look up information on an object using the dopfield expression function. This value will be -1 if the node does not process objects sequentially (such as the Group DOP).
This string contains a space separated list of the unique object identifiers for every object being processed by the current node.
This string contains a space separated list of the names of every object being processed by the current node.
This value is the simulation time (see variable ST) at which the current object was created.
Therefore, to check if an object was created
on the current timestep, the expression
$ST == $OBJCT should
always be used. This value will be zero if the node does not process
objects sequentially (such as the Group DOP).
This value is the simulation frame (see variable SF) at which the current object was created.
This value is equivalent to using the dopsttoframe expression on the OBJCT variable. This value will be zero if the node does not process objects sequentially (such as the Group DOP).
This is a string value containing the name of the object being processed.
Object names are not guaranteed to be unique within a simulation. However, if you name your objects carefully so that they are unique, the object name can be a much easier way to identify an object than the unique object identifier, OBJID.
The object name can
also be used to treat a number of similar objects (with the same
name) as a virtual group. If there are 20 objects named “myobject”,
strcmp($OBJNAME, "myobject") == 0 in the activation field
of a DOP will cause that DOP to operate only on those 20 objects. This
value will be the empty string if the node does not process objects
sequentially (such as the Group DOP).
This is a string value containing the full path of the current DOP Network. This value is most useful in DOP subnet digital assets where you want to know the path to the DOP Network that contains the node.
Most dynamics nodes have local variables with the same names as the node’s parameters. For example, in a Position node, you could write the expression:
$tx + 0.1
…to make the object move 0.1 units along the X axis at each timestep.