CreatureRenderer.cs

// I created a shared base-class for both CreatureRenderer and CreatureCanvasRenderer, which removes tons and tons of copy/pasted code...
// Here's how I transform the vertices...

    public void UpdateRenderingData() {
      CreatureRenderModule.UpdateRenderingData(
          creature_manager,
          counter_clockwise,
          ref vertices,
          ref normals,
          ref tangents,
          ref colors,
          ref uvs,
          creature_asset,
          skin_swap_active,
          active_animation_name,
          ref final_indices,
          ref final_skin_swap_indices,
          ref triangles,
          ref skin_swap_triangles);

      bool should_skin_swap = CreatureRenderModule.shouldSkinSwap(creature_asset, skin_swap_active, ref skin_swap_triangles);

      active_mesh.vertices = TransformVertices(vertices);
      active_mesh.colors32 = colors;
      active_mesh.triangles = should_skin_swap ? skin_swap_triangles : triangles;
      active_mesh.normals = normals;
      active_mesh.tangents = tangents;
      active_mesh.uv = uvs;
      //CreatureRenderModule.debugDrawBones(creature_manager.target_creature.render_composition.getRootBone ());
    }
    
    protected Rect _vertexBox = new Rect();
    protected Vector3 vertexOffset {
      get {
        if (_vertexBox.size.magnitude <= float.Epsilon) {
          _vertexBox = new Rect {
            xMin = float.MaxValue,
            yMin = float.MaxValue
          };
          foreach (Vector3 v in vertices) {
            if (v.x < _vertexBox.xMin) _vertexBox.xMin = v.x;
            if (v.x > _vertexBox.xMax) _vertexBox.xMax = v.x;
            if (v.y < _vertexBox.yMin) _vertexBox.yMin = v.y;
            if (v.y > _vertexBox.yMax) _vertexBox.yMax = v.y;
          }
        }
        return _vertexBox.center;
      }
    }

    protected virtual Vector3[] TransformVertices(Vector3[] vertices) {
      return vertices.Select(v => v - vertexOffset).ToArray();
    }

// -------------------------------------------------------------------
// In CreatureCanvasRenderer, I override the transform...


    protected override Vector3[] TransformVertices(Vector3[] vertices) {
      RectTransform canvasRect = canvas.transform as RectTransform;
      return vertices.Select(
        v => new Vector3(
          (v.x - vertexOffset.x) / canvasRect.localScale.x,
          (v.y - vertexOffset.y) / canvasRect.localScale.y,
          v.z
        )
      ).ToArray();
    }