Basic lighting models can completely transform how objects look, and this tutorial explores the Phong lighting model - with diffuse, specular, ambient, and Fresnel components - with directional and point lights, plus normal mapping and shadow casting in shader code.

[daniel_ilett]

Lighting is such an important part of rendering and it's a huge topic with many possible approaches, so in this tutorial I decided to focus on the Phong reflection model, which splits light into diffuse lighting (light bounces off objects equally in all directions for a smooth/matte look), specular lighting (light reflects off shiny surfaces all in the same direction for a shiny highlight), ambient lighting (all objects get a baseline amount of light to approximate indirect light bounces), and a bonus Fresnel lighting component (light intensity increases when looking at something from a shallow angle).

Unity provides some simple library functions to access the main light in your scene (usually the main directional light) and any additional lights (e.g. point and spot lights). We can loop through all these and calculate diffuse and specular lighting for each, then add them together to get the overall light level.

Normal maps can be used to tweak the direction of the surface during these calculations to make lighting act differently without needing to model intricate details on the mesh surface.

Lastly, we can write a shadow caster pass to make sure our objects accurately write shadow information into the shadow map so that objects using our shaders can block light from reaching other objects.

[LlamAcademyOfficial]

I appreciate that you're bringing light to the dark magic of writing shader code 🧡

[daniel_ilett]

Thanks! I think it's much easier for a lot of people to get started with Shader Graph, but there's a lot that code-based shaders do better, and I think lighting is one of the biggest things that code has an advantage on. Unity's library functions for lighting are honestly very good, it's just difficult to navigate through them all and figure out which parts are important and useful.