//********************************************************
//                    Horizontal Sundial
//               NASS Sundial Design Tutorials
//             Part 2 Sundial Base and Hour Lines
//					Robert L. Kellogg, Ph.D.
//				          1 Jan 2020
//
//        This design is part of the creative commons
//********************************************************

/* Tutorial #1
   We're going to create the base of a sundial.  Three
   variation are given: a circular sundial and a dial base
   with 6 or 8 sides (hexagon or octagon).
   
   We'll make the sundial base with a slight taper of the
   sides. This is just a bit of simple esthetics.
 
   A goal of making this sundial is to create module
   procedures such that we can see each step and if we
   want, experiment with changes to the dial features
   
   Tutorial #2
   Then we add hour lines.  The base of the hour lines is
   moved off-center to the south by a distance Loffset.
   We've left enough room around the hour lines that we
   can add hour numbers in the next tutorial 
*/  

echo("Part-2 Drawing the Hour Angles");  //NASS Tutorial

// ----------------------------------------------------
// ---------------  Sundial Parameters ----------------
// ----------------------------------------------------
// Note:  base units are in mm and angles in degrees

shape   = "octagon";        // "circular"  dial base 
                            // "hexagon"   dial base
                            // "octagon"   dial base
                            
dial_btm    = 78;           //dial base diam (~3")  mm
dial_top    = 75;           //dial base (taper top) mm
dial_hght   = 3;            //dial base height      mm

lat         = 40;           //dial latitude         deg
minHA       = 5;            //first hour line  am   hour
maxHA       = 7;            //last hour line   pm   hour

Lwidth      = 1;            //hour line width       mm
Lhght       = 1;            //hour line height      mm
Llength     = dial_top;     //hour line length      mm
Loffset     = dial_top/4;   //hour line & gnomon offset

Dout        = .68*dial_top; //outer distance of chapter ring
Din         = .58*dial_top; //inner distance of chapter ring

// ----------------------------------------------------
// ------------  Main Program Starts Here -------------
// ----------------------------------------------------

if(shape=="circular") {
    echo("shape",shape);
    minangle = 3;
    sundial_base(minangle,turn=0);
}
if(shape=="octagon") {
    echo("shape",shape);
    minangle = 45;
    sundial_base(minangle,turn=45/2);
}
if(shape=="hexagon") {
    echo("shape",shape);
    minangle = 60;
    sundial_base(minangle,turn=0);
}

//add hour lines to the top of the sundial
hour_lines(minHA,maxHA,lat);

// ----------------------------------------------------
// ----------- Procedure Modules Start Here -----------
// ---------------------------------------------------- 
module hour_lines(minHA,maxHA,lat){
    // first and last hour angle in degrees
    first = 15*(minHA - 12);
    last  = 15*(maxHA);
    // loop through the hours
    for(HA=[first:15:last]){
        //theta is the hour line angle
        theta = atan2(sin(lat)*sin(HA),cos(HA));
        translate([0,0,dial_hght]){
            intersection(){
                //mask the raw hour angle
                donut_mask(Din,Dout,Lhght);
                translate([0,-Loffset,0])
                // raw hour angle
                rotate([0,0,theta])
                translate([0,Llength/2,Lhght/2])
                cube([Lwidth,Llength,Lhght],center=true);
            }
        }   
    }    
}

module donut_mask(Din, Dout, Dhght){
    //set the cylinder with 180 faces (2 deg segments
    $fn = 180;
    //subtract inner cylinder from the outer cylinder
    difference(){
        cylinder(d=Dout,h=Dhght);
        cylinder(d=Din,h=3*Dhght,center=true);
    }
}
    
module sundial_base(mini,turn){
    //create a multi-edge sundial
    $fa = mini;
    rotate([0,0,turn])
    cylinder($fa,h=dial_hght,d1=dial_btm,d2=dial_top);
}