While taking a look at the code mentioned in the previous post, I noticed two things. First, the PointCloud.pde file drops directly into OpenGL-specific code (rather than Processing API) for sake of speed to draw thousands and thousands of points. It’s further proof that I need to finish the PShape class for Processing 1.0, which will automatically handle this sort of thing automatically.

Second is a more general point about parsing. This isn’t intended as a nitpick on Aaron’s code (it’s commendable that he put his code out there for everyone to see—and uh, nitpick about). But seeing how it was written reminded me that most people don’t know about the casts in Processing, particularly when applied to whole arrays, and this can be really useful when parsing data.

To convert a String to a float (or int) in Processing, you can use a cast, for instance:

String s = "667.12";
float f = float(s);

This also in fact works with String[] arrays, like the kind returned by the split() method while parsing data. For instance, in SceneViewer.pde, the code currently reads:

String[] thisLine = split(raw[i], ",");
points[i * 3] = new Float(thisLine[0]).floatValue() / 1000;
points[i * 3 + 1] = new Float(thisLine[1]).floatValue() / 1000;
points[i * 3 + 2] = new Float(thisLine[2]).floatValue() / 1000;

Which could be written more cleanly as:

String[] thisLine = split(raw[i], ",");
float[] f = float(thisLine);
points[i * 3 + 0] = f[0] / 1000;
points[i * 3 + 1] = f[1] / 1000;
points[i * 3 + 2] = f[2] / 1000;

However, to his credit, Aaron may have have intentionally skipped it in this case since he don’t need the whole line of numbers.

Or if you’re using the Processing API with Eclipse or some other IDE, that means that the float() cast won’t work for you. You can substitute float() with the parseFloat() method:

String[] thisLine = split(raw[i], ",");
float[] f = parseFloat(thisLine);
points[i * 3 + 0] = f[0] / 1000;
points[i * 3 + 1] = f[1] / 1000;
points[i * 3 + 2] = f[2] / 1000;

The same can be done for int, char, byte, and boolean. You can also go the other direction by converting float[] or int[] arrays to String[] arrays using the str() method. (The method is named str() because a String() cast would be awkward, a string() cast would be error prone, and it’s not really parseStr() either.)

When using parseInt() and parseFloat() (versus the int() and float() casts), it’s also possible to include a second parameter that specifies a “default” value for missing data. Normally, the default is Float.NaN for parseFloat(), or 0 with parseInt() and the others. When parsing integers, 0 and “no data” often have a very different meaning, in which case this can be helpful.