Mini Tutorial on Reflected Light

This is originally based on an overview I did in an art based Discord server that I later converted to a Bluesky thread that I am now recreating here as a blog style post. Fun!

So here it is, my ugly mini tutorial on REFLECTED LIGHT.

So we got some spheres here. Mine are stolen from the internet, more on that later.

Unlike in the demo image that I used up in the header (yeah the one with the annoying attention grabbing text), you'll notice that on this one there is a very very clear rounded shape cut in by the light. What's up with that?

Well, let's start at the beginning.

So obviously a cast shadow occurs because light is being blocked by a physical object.

Light is very directional! Rays move in straight lines. It's predictable and based on topography and angles. You can even reverse engineer things from shadows, like the highest point on the object, or where the light is and how wide the light source is.

So bounced light is, as the name suggests, when light hits a surface and then bounces off elsewhere, very much like a pool ball. In fact, if the surfaces where perfect and without defect it would move the same direction every time.

But materials are not perfect, so instead it scatters like an explosion. Depending on the qualities of the surface there will be more or less light shot off. Matte surfaces are very rough and capture a lot of light in their microscopic pockets, and glossy surfaces do the opposite. (And that's not even considering unusual cases like lenticular lenses or peacock feathers.)

So back to the sphere. Light clearly, visibly, CANNOT be bounced where the shadow is. Its too dark! If it were a half shadow, as in if there was a secondary light source, some of that could bounce back and make a soft reflected light on the back.

You can see this in the illustration below to some degree (even though its still a single light source, just at a different angle) or in the grid of pictures, which are 3D renders. (credit to roosdepot.tumblr.com/post/1104188... where you can download these and other renders in high res).

So where is the light bouncing from? The areas of light! And the longer it has to travel the weaker it is, thus the shade fall off - its brightest where the light has to travel the least distance. Just like a flashlight, or a light bulb.

Now a single point will be lit by many locations, additively, but the rays are still all too long to make much light. They could brighten the area more if the light were more intense, or closer to the sphere (lowering the travel distance and decreasing the energy lost during the journey).

I mentioned I stole those first two images from the net, right? Well, more accurately I stole them from sphere tutorials, both of which showed the harsh crescent shaped rim lighting that you see in the first image.

https://reddotgallery.com/sphere-tutorial

https://thevirtualinstructor.com/howtodrawasphere.html

You can get this kind of reflected highlight if it's next to another object, or a wall or something, but as demonstrated there should be a rounder highlight coming in from the bounced light of their surface plane which is absent in this illustration.

Here's a video of someone just moving a light around on a sphere. Watch is with everything I wrote in mind and it will all immediately make so much sense.

Oh and since I'm on the subject, that little white dot showing up on the very glossy ball below is the specular highlight. It is the mirror reflection of the light source. On items like cylinders it will look stretched out along the topography from the point closest to the light.

Some more thorough diagrams on what was discussed:

As always, check out my pinned post on Bluesky for more helpful stuff or throw me a tip/buy some stickers on my Ko-fi page so I can keep making free educational resources and art materials.

(Who am I kidding I know we're all broke)

Go with love. Everyone deserves to live and pursue their dreams.