I Interesting Optical Phenomenon

[bob012345]

TL;DR Summary

Light coming through tree branches makes two bright lines on the ground. Please help me identify what is happening. Thanks.

The lines have a slight purplish hue to them (at least reflected from leaves) and are about 2 feet apart. Here are images of the lines and the sun through the tree.

 

[Drakkith]

I'd guess it's either caused by the way the tree limbs are aligned with each other, or by reflection of sunlight off of another surface. Get down on the ground and stick your eye in one of the bright spots and then move back and forth along it. You should find out very quickly what's causing them.

 

[Ibix]

stick your eye in one of the bright spots

...carefully, because that's the Sun you're looking at. Putting your hand on one of the lines and back-tracing the light by moving your hand away while keeping its shadow on the line might be safer.

 

[bob012345]

I discovered what this effect is caused by. As @Drakkith suggested it's simple reflection from two vertical narrow windows on my next door neighbor's house. Here is a 2D model (looking down from above) although the sun is of course also at a vertical angle which explains why the lines have only a certain length on the ground. I discovered this by using a black surface to trace where the light originated from. Science!