include <BOSL2/std.scad>

include <BOSL2/turtle3d.scad>

include <BOSL2/paths.scad>

 module C1(angle,q, offset,ang){

	//------------------------------------	   

    yrot(angle)union(){

		ushape=turtle(

		  ["setdir",[0,-1],"ymove",3,"left","xmove",-18,"setdir",[-1,0],"arcleft",3,180,"xmove",18,"right","ymove",3]

		);

		ushape2=turtle(

		  ["setdir",[0,-1],

		  "ymove",3,

		  "left",

		  "xmove",-11.2,

		  "setdir",[-1,0],

		  "arcleft",19,30,

		  "arcleft",0.53,120,

		  "arcleft",19,30,

		  "xmove",11.2,

		  "right","ymove",3]

		);

        echo (ushape2);        

		ushape3=resample_path(ushape2,20,closed = true);

ushape4= [[0, 0], [0, 3], [-11.2, 3], [-11.543, 2.9969], [-11.8859, 2.98761], [-12.2286, 2.97213], [-12.571, 2.95047], [-12.9129, 2.92263], [-13.2543, 2.88862], [-13.5949, 2.84845], [-13.9348, 2.80214], [-14.2739, 2.7497], [-14.6119, 2.69115], [-14.9488, 2.62651], [-15.2844, 2.55579], [-15.6188, 2.47903], [-15.9517, 2.39624], [-16.283, 2.30745], [-16.6127, 2.2127], [-16.9407, 2.11201], [-17.2667, 2.00541], [-17.5908, 1.89295], [-17.9128, 1.77465], [-18.2326, 1.65056], [-18.5501, 1.52071], [-18.8653, 1.38516], [-19.1779, 1.24393], [-19.4879, 1.09709], [-19.7952, 0.94467], [-20.0998, 0.786729], [-20.4014, 0.623315], [-20.7, 0.454483], [-20.894, 0.260489], [-20.965, -0.00451079], [-20.894, -0.269511], [-20.7, -0.463504], [-20.4014, -0.632337], [-20.0998, -0.79575], [-19.7952, -0.953692], [-19.4879, -1.10611], [-19.1779, -1.25295], [-18.8653, -1.39418], [-18.5501, -1.52973], [-18.2326, -1.65958], [-17.9128, -1.78367], [-17.5908, -1.90197], [-17.2667, -2.01443], [-16.9407, -2.12103], [-16.6127, -2.22172], [-16.283, -2.31647], [-15.9517, -2.40526], [-15.6188, -2.48805], [-15.2844, -2.56481], [-14.9488, -2.63553], [-14.6119, -2.70017], [-14.2739, -2.75873], [-13.9348, -2.81117], [-13.5949, -2.85748], [-13.2543, -2.89764], [-12.9129, -2.93165], [-12.571, -2.95949], [-12.2286, -2.98116], [-11.8859, -2.99664], [-11.543, -3.00592], [-11.2, -3.00902], [3.55271e-15, -3.00902], [3.55271e-15, -0.00902158]];

	//	fwd(20)stroke(ushape,width=.1,closed=true);

		path1 = turtle3d([   

		         ["arc",40,"up", 23, "steps", 15, "grow",[1,1.5]],

				 ["arc",60,"down", 20, "steps", 15,"grow",[1,1.1]],

			     ["arc",60,"down", 20, "steps", 15,"shrink",[1,1.2]],

				 ["arc",155,"up",17, "steps", 15,"shrink",[1,1.2]],

                 ["move",45,"shrink",[1,1.1]] 

                ],

        state=move([0,0,0]),transforms=true);

        //ushape1=square([9,7]);

		ushape1=[[-18, -3],[-20,-1.5],[-20,1.5],[-18,3],[ 20, 3],[ 20, -3]];	

	//	fwd(20)stroke(ushape1,width=.1,closed=true);

		path2= turtle3d([     

		        ["arc",40,"up", 29, "steps", 15, "grow",[1,1.3]],

				["move",6, "grow",[1,1.1]]

                ],

                   state=LEFT,transforms=true);		 

difference(){ 

     union(){

        xrot(90) cyl(d=8,h=13,$fn=6); 

        top_half(s=300)

		  union(){	

			down(12.5)left(20){

            sweep(ushape4, path1,caps=true);	//перед

			sweep(ushape4, path2,caps=true);				}  //зад

			right(125+1){cylinder(d=7.5,h=7);

			%down(4.8)  {cylinder(d=2.5,h=17);

						 cylinder(d=19.7,h=4.8);}}	

			left(17)cylinder(d=10,h=5);

			yrot(5)down(10){left(36+12)scale([2.4,1,1])cylinder(d=12.8,h=21.7);

			up(21.7)left(36+12)scale([2.4,1,0.5])sphere(d=12.8);}

            up(7.8){hull()

			           {right(13.5)back(10)cylinder(d=7,h=6.2);

						right(9)cube([9,0.1,6.2]);}

                       }

	      }

	}  //union

 left(83)down(56)xrot(90)cyl(d=150,h=40);

 right(125+1)cylinder(d=2.5,h=8);

 right(9)fwd(20)cube([21.5,50,7.8]);

 right(12)fwd(5)cube([9.5,3,11]);

 xrot(90)cyl(d=2.5+0.3,h=22);  //ось

 up(7.8)right(13.5)back(10)cylinder(d=3,h=6.2);

 left(17)down(0.2)cylinder(d=7,h=3);

 } // diff

 } //offset

 } // C1

 C1(0,1,0,0);

I build shapes for turtle3d in turtle (2d)\ Then I diffs some and preview shows empty.\ I guess it not solid. ``` include <BOSL2/std.scad> ``` ``` include <BOSL2/turtle3d.scad> ``` ``` include <BOSL2/paths.scad> ``` ``` module C1(angle,q, offset,ang){ ``` ``` ``` ``` //------------------------------------ ``` ``` ``` ``` yrot(angle)union(){ ``` ``` ``` ``` ushape=turtle( ``` ``` ["setdir",[0,-1],"ymove",3,"left","xmove",-18,"setdir",[-1,0],"arcleft",3,180,"xmove",18,"right","ymove",3] ``` ``` ); ``` ``` ushape2=turtle( ``` ``` ["setdir",[0,-1], ``` ``` "ymove",3, ``` ``` "left", ``` ``` "xmove",-11.2, ``` ``` "setdir",[-1,0], ``` ``` "arcleft",19,30, ``` ``` "arcleft",0.53,120, ``` ``` "arcleft",19,30, ``` ``` "xmove",11.2, ``` ``` "right","ymove",3] ``` ``` ); ``` ``` echo (ushape2); ``` ``` ushape3=resample_path(ushape2,20,closed = true); ``` ``` ``` ``` ushape4= [[0, 0], [0, 3], [-11.2, 3], [-11.543, 2.9969], [-11.8859, 2.98761], [-12.2286, 2.97213], [-12.571, 2.95047], [-12.9129, 2.92263], [-13.2543, 2.88862], [-13.5949, 2.84845], [-13.9348, 2.80214], [-14.2739, 2.7497], [-14.6119, 2.69115], [-14.9488, 2.62651], [-15.2844, 2.55579], [-15.6188, 2.47903], [-15.9517, 2.39624], [-16.283, 2.30745], [-16.6127, 2.2127], [-16.9407, 2.11201], [-17.2667, 2.00541], [-17.5908, 1.89295], [-17.9128, 1.77465], [-18.2326, 1.65056], [-18.5501, 1.52071], [-18.8653, 1.38516], [-19.1779, 1.24393], [-19.4879, 1.09709], [-19.7952, 0.94467], [-20.0998, 0.786729], [-20.4014, 0.623315], [-20.7, 0.454483], [-20.894, 0.260489], [-20.965, -0.00451079], [-20.894, -0.269511], [-20.7, -0.463504], [-20.4014, -0.632337], [-20.0998, -0.79575], [-19.7952, -0.953692], [-19.4879, -1.10611], [-19.1779, -1.25295], [-18.8653, -1.39418], [-18.5501, -1.52973], [-18.2326, -1.65958], [-17.9128, -1.78367], [-17.5908, -1.90197], [-17.2667, -2.01443], [-16.9407, -2.12103], [-16.6127, -2.22172], [-16.283, -2.31647], [-15.9517, -2.40526], [-15.6188, -2.48805], [-15.2844, -2.56481], [-14.9488, -2.63553], [-14.6119, -2.70017], [-14.2739, -2.75873], [-13.9348, -2.81117], [-13.5949, -2.85748], [-13.2543, -2.89764], [-12.9129, -2.93165], [-12.571, -2.95949], [-12.2286, -2.98116], [-11.8859, -2.99664], [-11.543, -3.00592], [-11.2, -3.00902], [3.55271e-15, -3.00902], [3.55271e-15, -0.00902158]]; ``` ``` ``` ``` // fwd(20)stroke(ushape,width=.1,closed=true); ``` ``` ``` ``` path1 = turtle3d([ ``` ``` ["arc",40,"up", 23, "steps", 15, "grow",[1,1.5]], ``` ``` ["arc",60,"down", 20, "steps", 15,"grow",[1,1.1]], ``` ``` ["arc",60,"down", 20, "steps", 15,"shrink",[1,1.2]], ``` ``` ["arc",155,"up",17, "steps", 15,"shrink",[1,1.2]], ``` ``` ["move",45,"shrink",[1,1.1]] ``` ``` ], ``` ``` state=move([0,0,0]),transforms=true); ``` ``` //ushape1=square([9,7]); ``` ``` ushape1=[[-18, -3],[-20,-1.5],[-20,1.5],[-18,3],[ 20, 3],[ 20, -3]]; ``` ``` ``` ``` // fwd(20)stroke(ushape1,width=.1,closed=true); ``` ``` ``` ``` path2= turtle3d([ ``` ``` ["arc",40,"up", 29, "steps", 15, "grow",[1,1.3]], ``` ``` ["move",6, "grow",[1,1.1]] ``` ``` ], ``` ``` state=LEFT,transforms=true); ``` ``` ``` ``` ``` ``` difference(){ ``` ``` union(){ ``` ``` xrot(90) cyl(d=8,h=13,$fn=6); ``` ``` top_half(s=300) ``` ``` union(){ ``` ``` down(12.5)left(20){ ``` ``` sweep(ushape4, path1,caps=true); //перед ``` ``` sweep(ushape4, path2,caps=true); } //зад ``` ``` right(125+1){cylinder(d=7.5,h=7); ``` ``` %down(4.8) {cylinder(d=2.5,h=17); ``` ``` cylinder(d=19.7,h=4.8);}} ``` ``` left(17)cylinder(d=10,h=5); ``` ``` ``` ``` yrot(5)down(10){left(36+12)scale([2.4,1,1])cylinder(d=12.8,h=21.7); ``` ``` up(21.7)left(36+12)scale([2.4,1,0.5])sphere(d=12.8);} ``` ``` ``` ``` up(7.8){hull() ``` ``` {right(13.5)back(10)cylinder(d=7,h=6.2); ``` ``` right(9)cube([9,0.1,6.2]);} ``` ``` } ``` ``` } ``` ``` } //union ``` ``` ``` ``` left(83)down(56)xrot(90)cyl(d=150,h=40); ``` ``` right(125+1)cylinder(d=2.5,h=8); ``` ``` right(9)fwd(20)cube([21.5,50,7.8]); ``` ``` right(12)fwd(5)cube([9.5,3,11]); ``` ``` ``` ``` xrot(90)cyl(d=2.5+0.3,h=22); //ось ``` ``` up(7.8)right(13.5)back(10)cylinder(d=3,h=6.2); ``` ``` left(17)down(0.2)cylinder(d=7,h=3); ``` ``` } // diff ``` ``` } //offset ``` ``` } // C1 ``` ``` ``` ``` C1(0,1,0,0); ```

pics 

ushape4 = reverse([....]);

include <BOSL2/std.scad>
include <BOSL2/turtle3d.scad>
include <BOSL2/paths.scad>

ushape4= [[0, 0], [0, 3], [-11, 3], [-17, -2]];

path1 = turtle3d([[ "move", 10 ]],
    state=move([0,0,0]),transforms=true
);

top_half() sweep(ushape4, path1,caps=true);

Your model is ending up inside-out, and that's really messing up the previewer. If you look at it with View/Thrown Together, you can see that the main body of the model is magenta... that's bad; it means that we're looking at what is supposed to be the back side of the faces. This problem derives from ushape4 being wound backwards.  Reversing it, e.g. via ushape4 = reverse([....]); solves most of your problems. I don't know all of the rules for sweep, and in particular I don't know how to know which way is "correct".  In this particular case, you're winding it counter-clockwise, and it needs to be clockwise, but I don't know if that's different for other sweeps, e.g. a sweep in the opposite direction. Perhaps Adrian could chime in. By the way, when you're asking for help with a model, it's good to ensure that it is as small and simple as you can get it, and well-formatted.  That makes it a *lot* easier for a reviewer, and the process may help you to find the problem on your own. Here's a simplified version of your program that still demonstrates the problem: include <BOSL2/std.scad> include <BOSL2/turtle3d.scad> include <BOSL2/paths.scad> ushape4= [[0, 0], [0, 3], [-11, 3], [-17, -2]]; path1 = turtle3d([[ "move", 10 ]], state=move([0,0,0]),transforms=true ); top_half() sweep(ushape4, path1,caps=true);

Yes! it works now. I am understanding more\ Thank you!