Using DATs For Instancing

Fetched from Storage with a Script CHOP

This example follows from the previous with a variation in considering how you might approach smooth animation as data changes over time. Operators like the filter CHOP or lag CHOP are good candidates for creating smooth motion in these circumstances. Both of those operators, however, require that the data is already formatted in CHOPs. To avoid updating a table, and then converting that data to CHOPs, this example instead uses a script CHOP to pull the contents of storage directly into multi-sample CHOP format. The motivation for this style of approach again stems from the original discussion condition that the data would likely be formatted / ingested as a JOSN blob.

This example uses the same principles of data updating as we’ve previously seen. The primary difference in this example is the use of a script CHOP to move data from storage directly into CHOP format. A closer look at the script CHOP’s callback reveals what’s happening:

def onCook(scriptOp):
    # clear out the old data
    scriptOp.clear()

    # copy over the incomming data
    scriptOp.copy(scriptOp.inputs[0])

    # fetch our updated data from storage - we do that 
    # here rather than in the loop to make sure we're only
    # doing this once 
    data = parent().fetch('data')

    # add a channel called 'sy' to our CHOP
    scriptOp.appendChan('sy')

    # loop through all of our samples in the channel 'index'
    for each_sample in scriptOp['index'].vals:
        # CHOP values are always float vals, so to use our
        # 'index' as a look up in our dict we need to convert
        # to an integer 
        sample_id = int(each_sample)

        # the syntax here is operator[channel][sample index]
        # in this case scriptOp is the CHOP operator connected
        # to this callback. Then we want to target the 'sy'
        # channel, and the sample at the sample_id index.
        # That sample, the data from storage we want to use
        # is in data[sample_id]['sy']
        scriptOp['sy'][sample_id] = data[sample_id]['sy']
    return

After being converted to a CHOP format a filter CHOP is used to smoothly blend between positions.

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Tested in TouchDesigner099 2020.23680

Updated 06.03.20
Matthew Ragan
Zoe Sandoval