Thank you, I will look into it!
//edit
I think I did not do a very good job describing this whole endavour. Here's my second try:
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I got a request from my colleague to visualize data which was aquired directly from the interface of an electrical drive city bus. This electical drive engine is new and the client wants to visualize the live battery data (and something more) on his website via splitscreen: a view of the bus driving on the left side and the corresponding live data on the right side, visualized as a digital dashboard.
It is going to look like this:
The data from the bus I'm about to describe was grabbed 50 times per second to a CSV file, which means I have 50 values for each parameter every second to work with.
So the csv file I received looked like this:
After removing everthing I did not need for further work, I got this:
After importing it to After Effects I realised it won't do me no good as long as it's not in JSON file format so I converted the CSV to JSON which then looked like this:
In After Effects it finally looks like I could work with those values:
You see After Effects interprets the JSON file in a two dimensional way: dataValue([x,y]) whereas x represents the number of entry and y stands for the entry's parameter (0 = speed, 1 = engine, 2 = steer, 3 = charge)
Now the most basic thing I want is to have my text layer in after effects just show me the "speed" value. But it needs to change according to this JSON table. So for instance, if I look at frame 0 in my comp the text value should display the very first speed value taken from the first entry of the JSON file (which is called "dataValue([0,0])" in After effects. When I look at frame 136 the text should grab its value from "dataValue([136,0])"
I could pick whip the text layer's source parameter to one of those values, but then I only have one constant value. I somehow need to map it to the second dimension ("x") and tell After Effects the first dimension ("x") should always be the same as the current frame the comp is in.
Do you have any clue how to write this expression?
Thanks a ton!
Stefan
OK, first thing - unless your data contains complex objects, forget JSON. After Effects can read CSV or TSV files just fine, and more efficiently since there's less packing. Remember the data file is read continually just in case a value has updated, that's the point behind the "dynamic" data feature.
Let's suppose you have a CSV file that begins something like this...
Speed,Battery,Gear
80,99.6,D
82,99.5,D
81,99.4,D
etc.
In scripting, row and column counts begin at zero, so the "data " for speed starts at [0,1] - ignoring the column header - and continues [0,2] ... [0,3].... etc.
It's important to have the header row as we'll see shortly.
Second thing - don't put your data into the composition as a layer. You simply read it from the project panel directly.
So, import the CSV file - let's say it's called "data.csv" - and create a text layer in your composition. Twirl down to "Source Text" and alt-click the stopwatch to create an expression.
Assuming your composition is running at 50fps and the data is 50 samples/sec, all you need to get is the data point for the frame number (since frame numbers begin at 1, that header row in the file is automatically ignored). You get the frame number using timeToFrames(), and you get a CSV cell using dataValue()... so for "speed" write this in the expression:
t = timeToFrames();
footage("data.csv").dataValue( [0,t] )
For "gear" just change the column number
t = timeToFrames();
footage("data.csv").dataValue( [2,t] )
If the composition frame rate doesn't match the sample rate, insert a line that does some math with "t" before using it. If your composition is NTSC 29.97 and your sample rate is 50Hz, that math will hurt. Blame the NTSC.
Notes:
- Rather that writing footage("data.csv") every time you can pickwhip the data file directly from the project panel while the expression editor is open.
- You must have enough data - if AE reads beyond the end of a file, it'll throw an error. To "pause" on the last entry, you can use a simple restriction on the value of t, such as if (t>1000) t = 1000;
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