What are the best practices for optimizing shaders for game engines?

A material is an instance of a shader using specific values, texture maps, etc, while a shader is the function itself that determines material response, mathematical calculations, and exposed parameters. This section is confusing because it does not explain their relationship.

It is very important to keep in mind that each software will have their own way of handling shaders... that's why you can't simply, for example, create a material/shader inside Blender and directly export it into Unreal Engine. You will have to either "bake" it in the form of maps (diffuse, roughness, normals...) and/or rebuild it in the target software. While there is common practices like PBR material maps, each rendering engine will have its own way of handling things like shadows, translucency, ect...

Materials can provide life into your model by affecting various properties basically on how light interacts with them on different levels. They serve as a potent tool for incorporating details like dirt, dust, and surface imperfections such as scratches or damages. Pro tip: Roughness becomes crucial in crafting Anisotropic materials like CDs or various metals. It not only enhances realism but also functions as a canvas for artistic expression, allowing you to layer on details that bring depth to your materials.

Though the options listed are the main programs for rendering materials, I would include Adobe Substance Painter. Substance Painter allows you to take significantly more control over the textures you create, allowing you to procedurally and manually add your own details, rather than being limited to only a plain material or pre-existing tiled texture.

Gray world with uniform materials lacks the diverse surfaces that bring your 3D art closer to reality. Additionally, they simplify adding detail by working directly on your maps like normal or height, So you don’t need to model every detail on your models Pro tip: To optimize materials further, explore shaders enabling the use of multiple maps on different channels within a single image. For instance, in Substance Designer, the RBA split feature facilitates combining height, roughness, and metallic details on a single image.

Love that your helping people interested in modeling. Please make a heavy emphasis on topology. Blender had saturated the internet with unusable meshes

A shader variant is created for each permutation of a shader’s properties. This includes keywords and file sizes. So if two mesh share the same shader but different textures, two shader variants would be created. Shader variants are necessary but can slow your game down in various ways if they aren’t kept in check. Minimize the number of shader variants by using a texture atlas and fewer materials. Use vertex colors to add shading instead of light maps. Use dynamic shader batching and preloaded shader bundles to reduce lag spikes. Use larger light maps to reduce the number of light maps texture files. each light map texture can introduce more shader variants.

LOD systems, batching, instancing, culling, and occlusion are essential, but to truly optimize, dive deeper. ORM (Occlusion, Roughness, Metallic) or NRA (Normal, Roughness, Ambient Occlusion) texture packing consolidates shader data, streamlining the rendering process. GLSL code optimization, like minimizing conditional statements and reusing calculations, is pivotal. It's not just about reducing data but efficiently processing it. Embrace modern practices, and always consider the intricacies of the target platform you're on.

You should also try to re-use shaders/materials as much as possible and use tricks like channel-packed textures and material instances to reduce draw-calls. If you are using procedural shaders, try to find a way to bake them before they are rendered.