README.md

Satin

A lightweight Fabric library for OpenGL shader usage.

---

Adding Satin to your project

You can add the library by inserting the following in your build.gradle (Requires Loom 0.2.4+):

repositories {
    jcenter()
}

dependencies {
    modImplementation "io.github.ladysnake:Satin:${satin_version}"
    // Include Satin as a Jar-in-Jar dependency (optional)
    include "io.github.ladysnake:Satin:${satin_version}"
}

You can then add the library version to your gradle.propertiesfile:

# Satin library
satin_version = 1.x.y

You can find the current version of Satin in the releases tab of the repository on Github.

If you wish your mod to be 100% standalone, you also need to include the fabric-api-base and fabric-resource-loader-v0 modules from Fabric API in your mod jar.

Using Satin

Changes to Vanilla

Simply having Satin installed alters the game in a few ways, mainly related to ShaderEffects.

• Uniform fix: Using a vector of integers as a uniform crashes the game in Vanilla because of a bad copy paste. Satin redirects a call to upload the right buffer.
• Shader locations: Satin patches JsonGlProgram to accept a resource domain in the specification of a program name and of a fragment/vertex shader file.
• Readable depth: Satin offered access to a Framebuffer's depth texture before it was cool (superseded in 1.16).

Satin does not set the shader in GameRenderer, except if a mod registers a PickEntityShaderCallback.

Shader Management

Satin's main feature is the Shader Effect management facility.

ShaderEffect is a Minecraft class implementing data driven post processing shaders, with a few caveats. First, those shader effects are initialized immediately at construction, but they must be initialized after the game has finished loading to avoid gl errors. Then, they must be updated each time the game's resolution changes. Finally, they do not have any way of setting uniforms from external code.

Satin can manage a shader effect for you, giving you a ManagedShaderEffect object. This shader effect is lazily initialized - although it can be initialized manually at any time. Initialized shader effects will be automatically reloaded each time the game's resolution changes, and during resource reloading. It also provides a number of access methods to set uniforms dynamically.

Here is the whole java code for a mod that applies a basic shader to the game:

public class GreyscaleMinecraft implements ClientModInitializer {
    private static final ManagedShaderEffect GREYSCALE_SHADER = ShaderEffectManager.getInstance()
    		.manage(new Identifier("shaderexample", "shaders/post/greyscale.json"));
    private static boolean enabled = true;  // can be disabled whenever you want
    
    @Override
    public void onInitializeClient() {
        // the render method of the shader will be called after the game
        // has drawn the world on the main framebuffer, when it renders
        // vanilla post process shaders
    	ShaderEffectRenderCallback.EVENT.register(tickDelta -> {
    	    if (enabled) {
                GREYSCALE_SHADER.render(tickDelta);
            }
    	});
    }
}

For examples of json shader definitions, look for the assets/minecraft/shaders folder in the minecraft source (description of those shaders can be found on the Minecraft Wiki). There is also a real application of this library in Requiem.

RenderLayer Utilities

The ManagedFramebuffer and ManagedShaderProgram classes have methods to obtain clones of existing RenderLayer objects, with a custom Target. This target causes draw calls to happen on the ManagedFramebuffer for the former, or using the shader program for the latter. This can be notably used to render custom effects on entities and block entities.

For examples of entities using those, see the relevant test mod.

Regular blocks do not support custom render layers. For advanced shader materials, you should consider using an alternative renderer like Canvas.

Shader Utilities

Satin has a few utility classes and methods to facilitate working with shaders, not limited to ShaderEffect. ShaderLoader provides a way to load, create and link OpenGL shader programs through a single method call, GlPrograms offer helper methods that operate on those programs, and the matrix package helps with matrix retrieval and manipulation. More information is available in the javadoc.

Events

Satin adds in a few events for rendering purposes / related to shaders. Currently, there are 5 available callbacks:

• EntitiesPostRenderCallback: fired between entity rendering end and block entity rendering start
• PickEntityShaderCallback: allows mods to add their own entity view shaders
• PostWorldRenderCallback: allows mods to render things between the moment minecraft finishes rendering the world and the moment it starts rendering HUD's and GUI's
• ResolutionChangeCallback: allows mods to react to resolution changes
• ShaderEffectRenderCallback: fired at the time vanilla renders their post process shaders

Note that those events may move to a more dedicated library at some point.

Full documentation

This repository's wiki provides documentation to write and use shaders with Satin API.