Color space term? (RGB / I values)

Question

I found ascii document with 3d data. It was said:

ascii text file of point cloud with RGB / I values

Here you can see part of document:

• 0.805, 10.301, -1.860, 165, 66, 65, 66
• 0.806, 10.311, -1.859, 157, 66, 65, 74
• 0.820, 10.298, -1.859, 209, 66, 65, 74

I did not found help on this format and cannot understand what is I values. Is there such a term "RGB / I values" in color theory?

Answer 1

In 3D applications, I (for "Intensity") is used to indicate the brightness of a light source whose color is defined using R. G and B values that are usually normalized (fit into range of 0 to 1). It's not really a part of color theory; it's part of how lights are defined in a 3D environment so that things like fall-off, specular reflections, etc., can be calculated. That may be what you have in this case, although it's hard to tell without a bit more context.