Spotlights
The second image below illustrates some experiments with Maya's spotlights. I was wondering how a spotlight's distance from the object it illuminates affects the spotlight's light. Also, what happens to the light from the center of the beam to its edge given various decays, dropoffs, and with and without a penumbra?
For this, I shined thirteen sets of three spotlights on a NURBS plane. The first column of spotlights (A) were 50 units away, the second (B) 5 units, and the third (C) about half a unit away. The cone angles were adjusted so that the circle of illumination for all three lights was the same before modifications to the lights' parameters. The center and the outside edges of each beam were marked with a dot. The spotlights all start with intensity = 1, penumbra = 0, dropoff = 0, and decay = none; just the distances and cone angles are different. (This is shown in row 1.) Starting from that as a base case (number 1 below), I make the changes shown in numbers 2 through 13:
- base (no changes) — intensity = 1, penumbra = 0, dropoff = 0, decay = none
- decay = linear
- decay = quadratic
- decay = quadratic, intensity = 10
- decay = cubic
- decay = cubic, intensity = 100
- dropoff = 1
- dropoff = 10
- dropoff = 20
- penumbra = -10
- penumber = -10, dropoff = 1
- penumbra = -10, dropoff = 20
- penumbra = -10, dropoff = 40
Superimposed over each spotlight's illumination is a histogram of a one-tall sample of that beam from the center dot to the red dot. The histograms show the distribution, from balck on the left to whits on the right, of the pixels in that line from center to edge.
The third image adds barndoors to the lights in the second image. The lights in column A have barndoors at 1.5 degrees, column B has 14 degrees, and column C has 50 degrees.
The Maya scene files are here and here (with barndoors).
A higher resolution version (~2MB) of the second image is also available.
A higher resolution version (~2MB) of the third image (with barndoors) is also available.
