cad-implicit-skill

Implicit CAD

Use this skill for implicit CAD models that should run directly in CAD Viewer as browser JS modules. The primary artifact is a .implicit.js or .implicit.mjs.

This skill is experimental. ALWAYS prefer conventional STEP-first CAD workflows unless the user explicitly asks for an implicit model.

File Format

An implicit CAD file is an ES module exporting an implicit.js/0.1.0 object. The schema source of truth lives in the bundled package at scripts/packages/implicitjs/src/lib/implicitCad/schema.js; scripts/lib/implicit-cad.mjs re-exports it as SCHEMA for helper-authored modules.

export default {
  schema: "implicit.js/0.1.0",
  name: "rounded capsule block",
  glsl: `
float sdf(vec3 p) {
  float sphere = implicit_sphere(p, vec3(0.0), 22.0);
  float block = implicit_box_centered(p, vec3(34.0, 18.0, 18.0), vec3(0.0));
  return implicit_union_round(sphere, block, 3.0);
}

vec3 color(vec3 p, vec3 normal) {
  return mix(vec3(0.20, 0.55, 0.95), vec3(0.95, 0.45, 0.20), smoothstep(-15.0, 20.0, p.z));
}
`,
};

Models may also declare params and animations. Parameter definitions use the implicitjs control schema: number, boolean, enum/select, color, string, and button. Number, boolean, color, and button params automatically become GLSL uniforms with the same name; do not add a separate uniforms object. bounds is optional and is estimated from the SDF when omitted; add explicit bounds only when the auto estimate is too broad, too slow, or misses an unusual field. bounds and render may be JavaScript functions that receive { ...params, params, animation, animationState, elapsedSec, progress, t }.

Built-in GLSL helpers use the implicit_* namespace, for example implicit_sphere, implicit_box_centered, and implicit_union_round.

export default {
  schema: "implicit.js/0.1.0",
  name: "breathing orb",
  params: {
    radius: {
      type: "number",
      label: "Radius",
      min: 12,
      max: 34,
      default: 22,
      unit: "mm",
    },
  },
  animations: {
    breathe: {
      label: "Breathe",
      duration: 3,
      update({ progress, set }) {
        set("radius", 18 + Math.sin(progress * Math.PI) * 10);
      },
    },
  },
  render: { steps: 224, epsilon: 0.004 },
  glsl: `
float sdf(vec3 p) {
  return length(p) - radius;
}

vec3 color(vec3 p, vec3 normal) {
  return mix(vec3(0.10, 0.58, 0.95), vec3(1.0, 0.34, 0.12), smoothstep(-18.0, 18.0, p.z));
}
`,
};