Casting a Shadow

This week, I continued working on studies regarding how light interacts with shapes in drawings.

First, these images show how light interacts with spheres. With a single light source, only the half of the sphere facing towards the light gets lit up. The other half remains in shadow. However, as long as there's anything behind the sphere, the darkest part of the shadow is not on the far side from the light source, but right on the border between the light and dark side. This is because of reflected light hitting whatever is behind the sphere and bouncing back towards it.

When an object is casting a shadow, in general, the closer the light source is to the object, the shorter the shadow being cast. A similar effect can also be achieved by raising the light source further from whatever surface the object is resting on.

Figuring out what area is covered by a 3D object's shadow can be determined by drawing a line straight down from the light source to whatever spot is directly beneath it. Then, the corners of the shadow can be found by tracing out triangles using that line as one of the sides. The remaining sides of the triangles pass through the top and bottom corners of the object respectively. Where they intersect is where the corners of the object's shadow lie.

Drawin the shadow cast by a sphere is a bit more complicated, but is basically the same. The boundaries of the shadow are defined by triangles that use a line going from the light source straight to the ground as one of their sides.

Changing the height of the object casting the shadow, as well as its position relative to the light source, can have a profound effect on the shadow being cast.

That's all for this week! See you next time!