I want a light source to put out a sheet or fan of light. It would illuminate only along a line if it were shining on a flat surface. But I want to shine this on complex shapes.
One way I've tried is to put a point light or emitting object between two closely spaced parallel planes. It can cast a line of light if I crank up the sample count to several thousand, but it's noisy, not well collimated, and of course slow. This is for an animation.