1. Backpack and strap parameters

Place within Main = { … }, outside other folders.

    AnyVar PackMass = 10.0;
    AnyVar g = 9.81;

    AnyVar PackH = 0.45;
    AnyVar PackW = 0.34;
    AnyVar PackThick = 0.12;

    AnyVar BackX = -0.05;
    AnyVar PackTopY = 0.35;
    AnyVar PackCenterY = PackTopY - PackH/2;

    AnyVar PackStrapX = BackX - 0.005;
    AnyVar PackStrapTopZ = 0.10;
    AnyVar PackStrapBottomZ = 0.17;
    AnyVar PackStrapBottomOffset = 0.03;

    AnyVar ShoulderX = 0.03;
    AnyVar ShoulderY = 0.46;
    AnyVar ShoulderZ = 0.18;

    AnyVar FrontStrapX = 0.10;
    AnyVar FrontStrapY = 0.24;
    AnyVar FrontStrapZ = 0.19;

2. Backpack body and attachment points

This excerpt belongs inside:

Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg = { … }

    AnyRefNode PackCentre = {
      sRel = {
        Main.BackX - Main.PackThick/2,
        Main.PackCenterY,
        0
      };

      AnyVec3 Color = {0.05, 0.25, 0.75};
      AnyVar Opacity = 0.90;
      AnyVar Transparency = 0.10;

      AnyVec3 Size = {
        Main.PackThick,
        Main.PackH,
        Main.PackW
      };

      #include "../../../Body/AAUHuman/ToolBox/DrawObjects/Box.any"
    };

    // Right upper attachment
    AnyRefNode PackTopStrapR = {
      sRel = {
        Main.PackStrapX,
        Main.PackTopY,
        Main.PackStrapTopZ
      };
    };

    // Left upper attachment
    AnyRefNode PackTopStrapL = {
      sRel = {
        Main.PackStrapX,
        Main.PackTopY,
        -Main.PackStrapTopZ
      };
    };

    // Right lower attachment
    AnyRefNode PackBottomStrapR = {
      sRel = {
        Main.PackStrapX,
        Main.PackTopY - Main.PackH + Main.PackStrapBottomOffset,
        Main.PackStrapBottomZ
      };
    };

    // Left lower attachment
    AnyRefNode PackBottomStrapL = {
      sRel = {
        Main.PackStrapX,
        Main.PackTopY - Main.PackH + Main.PackStrapBottomOffset,
        -Main.PackStrapBottomZ
      };
    };

3. Custom shoulder and front-of-torso path points

This excerpt also belongs inside:

Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg = { … }

    AnyRefNode StrapR = {
      sRel = {
        Main.ShoulderX,
        Main.ShoulderY,
        Main.ShoulderZ
      };
    };

    AnyRefNode StrapL = {
      sRel = {
        Main.ShoulderX,
        Main.ShoulderY,
        -Main.ShoulderZ
      };
    };

    AnyRefNode StrapFrontR = {
      sRel = {
        Main.FrontStrapX,
        Main.FrontStrapY,
        Main.FrontStrapZ
      };
    };

    AnyRefNode StrapFrontL = {
      sRel = {
        Main.FrontStrapX,
        Main.FrontStrapY,
        -Main.FrontStrapZ
      };
    };

4. Strap path definitions

This excerpt belongs inside Main.Model = { … }, after the model environment and drivers are defined.

    AnyFolder BackpackStraps = {

      // Right shoulder strap
      AnyKinPLine RightShoulderStrap = {
        AnyRefNode &ref1 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.PackTopStrapR;

        AnyRefNode &ref2 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.StrapR;

        AnyRefNode &ref3 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.StrapFrontR;

        AnyRefNode &ref4 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.PackBottomStrapR;

        AnyDrawPLine DrawRightStrap = {
          Thickness = 0.018;
          RGB = {0.75, 0.05, 0.05};
        };
      };

      // Left shoulder strap
      AnyKinPLine LeftShoulderStrap = {
        AnyRefNode &ref1 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.PackTopStrapL;

        AnyRefNode &ref2 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.StrapL;

        AnyRefNode &ref3 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.StrapFrontL;

        AnyRefNode &ref4 =
          Main.HumanModel.BodyModel.Trunk.SegmentsThorax.ThoraxSeg.PackBottomStrapL;

        AnyDrawPLine DrawLeftStrap = {
          Thickness = 0.018;
          RGB = {0.75, 0.05, 0.05};
        };
      };

    }; // End BackpackStraps

Note for AnyBody Support

The coordinates are initial estimates. The main issue is that the
displayed straps indent inward around the shoulder region and do not
appear symmetric in the posterior view. Please advise on recommended
anatomical reference frames/nodes and strap-path construction for
AnyBody Modeling System 6.0.