In three js there is an option to use directional light which is one of several types of light to choose from. Other options that I find myself using the most thus far include point lights, and ambient light, but in some cases I might want to use directional light in place of or on top of those options that I seem to prefer.
A directional light is like ambient light in the sense that it is a good way to go about simulating day light, but it is not the same thing as the light is coming from a certain direction to a certain target location, rather than just a base light intensity for all materials in a scene as is the case with ambient light. A directional light is also like a spot light in the sense that it is coming from a certain location to a certain target location, but not in a cone like manner.
So here we have a basic example of a directional light as a way to have some light in a scene that will work with a material that responds to light. To create an instance of directional light in three js I just need to call the THREE.DirectionalLight constructor. When calling the constructor I can pass a color as the fist argument, and an intensity level as a value between zero and one as the second argument.
By default the position of the directional light is 0,1,0 and the target of the directional light is the origin at 0,0,0.
A directional light like most lights and objects that are placed in a scene in three js inherits from the object 3d class, so it has a position property than can be used to set the position of the directional light to a point other than that of the default position.
Changing the position of the directional light is just on f two points of interest when it comes to changing the direction of the light. The other point of interest is the target property of the directional light that can also be changed to something other than the default as well.
So I am thinking that directional light might be one of the best choices when it comes to simulating sunlight. Still I think that I might only want to use directional light in conjunction with at least one additional light source such as ambient light. So in this example I am working out the beginnings of a very simple outdoor scene that will juts make use of a mesh made with the Box geometry as a way to represent a house, and a plain geometry based mesh to represent ground.
When this is up and running I have directional light working as expected, but when the direction light is not longer hitting the surface of a mesh the ambient light is still doing its thing to make sure that there is still a base amount of light.
I went a little farther with the house example of this post and ended up making a slightly more advanced model of a house that is not just a box geometry but a group of meshes being used together to create something that I am calling a house. If you would like to check it out it is one of my many three.js example posts, I have it listed there along with all the other basic project examples I have together thus far.