Shaders

R3NE compositions are compiled to Metal at runtime. The Custom Shader node lets you drop your own Metal Shading Language (MSL) fragment into the graph and have it rebuild as you type.

Anatomy of a node shader

A custom shader is a fragment function that receives the upstream texture and any uniforms you declare. R3NE wraps your function in a full-screen pass and binds parameters to inspector controls.

#include <metal_stdlib>
using namespace metal;

struct Params {
    float intensity;   // exposed as a slider 0..1
    float2 center;     // exposed as a 2D pad
};

fragment float4 main_image(
    float2 uv [[stage_in]],
    texture2d<float> src [[texture(0)]],
    constant Params& p  [[buffer(0)]]
) {
    constexpr sampler s(filter::linear, address::clamp_to_edge);
    float2 d = uv - p.center;
    float r = length(d);
    float pinch = 1.0 - p.intensity * exp(-r * r * 8.0);
    float4 c = src.sample(s, p.center + d * pinch);
    return c;
}

Live recompile

• Edit the shader inside R3NE or in your editor of choice, files are watched.
• Compile errors surface in the inspector with line numbers; the last good pipeline keeps running so the show never goes black.
• Uniforms in your Params struct become inspector controls automatically, annotate them with // @range comments to set min/max.

What’s next

• Combine shaders with MCP to let a model author and tweak nodes from natural language.
• Compute kernels and multi-pass shaders, coming after 1.0.