stretch factor in cylindrical equidistant and cylindrical equi-area models

config.cpp

@@ -254,6 +254,7 @@ void initConfig() {
   addsaverenum(stereo::mode, "stereo-mode");
   addsaver(vid.euclid_to_sphere, "euclid to sphere projection", 1.5);
   addsaver(vid.twopoint_param, "twopoint parameter", 1);
+  addsaver(vid.stretch, "stretch", 1);
   
   addsaver(gp::on, "goldberg", false);
   addsaver(gp::param.first, "goldberg-x", gp::param.first);

conformal.cpp

@@ -640,6 +640,10 @@ namespace conformal {
     if(pmodel == mdTwoPoint) {
       dialog::addSelItem(XLAT("parameter"), fts3(vid.twopoint_param), 'l');
       }
+
+    if(among(pmodel, mdBandEquidistant, mdBandEquiarea)) {
+      dialog::addSelItem(XLAT("parameter"), fts3(vid.stretch), 'l');
+      }
       
     dialog::addBreak(100);
     dialog::addItem(XLAT("history mode"), 'a');
@@ -685,6 +689,10 @@ namespace conformal {
 #endif
       else if(uni == 'l' && pmodel == mdHalfplane)
         lower_halfplane = !lower_halfplane;
+      else if(uni == 'l' && among(pmodel, mdBandEquiarea, mdBandEquidistant))
+        dialog::editNumber(vid.stretch, 0, 10, .1, 1, XLAT("parameter"), 
+          "Vertical stretch factor."
+          );
       else if(uni == 'a')
         pushScreen(history_menu);
       else if(uni == 'l' && pmodel == mdHemisphere && euclid)  {

dialogs.cpp

@@ -748,6 +748,11 @@ namespace dialog {
       addSelItem("generation range bonus", its(genrange_bonus), 'o');
       addSelItem("game range bonus", its(gamerange_bonus), 'O');
       }
+    
+    if(ne.editwhat == &vid.stretch && sphere && pmodel == mdBandEquiarea) {
+      addBoolItem("Gall-Peters", vid.stretch == 2, 'o');
+      add_action([] { vid.stretch = 2; });
+      }
 
     if(ne.editwhat == &vid.linewidth)
       addBoolItem("finer lines at the boundary", vid.antialias & AA_LINEWIDTH, 'o');

hyper.h

@@ -806,7 +806,7 @@ extern reaction_t help_delegate;
 
 struct videopar {
   ld scale, alpha, sspeed, mspeed, yshift, camera_angle;
-  ld ballangle, ballproj, euclid_to_sphere, twopoint_param;
+  ld ballangle, ballproj, euclid_to_sphere, twopoint_param, stretch;
   int mobilecompasssize;
   int aurastr, aurasmoothen;
 

hypgraph.cpp

@@ -276,44 +276,62 @@ void applymodel(hyperpoint H, hyperpoint& ret) {
         else if(H[2] < 0 && x <= 0) x = -M_PI - x;
         }
       hypot_zlev(zlev_used, y, zlev, yf, zf);
-      if(pmodel == mdTwoPoint) {
+      
-        auto p = vid.twopoint_param;
+      switch(pmodel) {
-        ld dleft = hypot_auto(x-p, y);
+        case mdTwoPoint: {
-        ld dright = hypot_auto(x+p, y);
+          auto p = vid.twopoint_param;
-        if(sphere) {
+          ld dleft = hypot_auto(x-p, y);
-          int tss = twopoint_sphere_flips;
+          ld dright = hypot_auto(x+p, y);
-          if(tss&1) { tss--; 
+          if(sphere) {
-            dleft = 2*M_PI - 2*p - dleft;
+            int tss = twopoint_sphere_flips;
-            dright = 2*M_PI - 2*p - dright;
+            if(tss&1) { tss--; 
-            swap(dleft, dright);
+              dleft = 2*M_PI - 2*p - dleft;
-            y = -y;
+              dright = 2*M_PI - 2*p - dright;
-            }
+              swap(dleft, dright);
-          while(tss) { tss -= 2;
+              y = -y;
-            dleft = 2*M_PI - 4*p + dleft;
+              }
-            dright = 2*M_PI - 4*p + dright;
+            while(tss) { tss -= 2;
+              dleft = 2*M_PI - 4*p + dleft;
+              dright = 2*M_PI - 4*p + dright;
+              }
             }
+          x = (dright*dright-dleft*dleft) / 4 / p;
+          y = (y>0?1:-1) * sqrt(dleft * dleft - (x-p)*(x-p) + 1e-9);
+          break;
+          }
+        case mdBand: {
+          switch(cgclass) {
+            case gcSphere:
+              y = atanh(sin(y));
+              x *= 2; y *= 2;
+              break;
+            case gcHyperbolic:
+              y = 2 * atan(tanh(y/2));
+              x *= 2; y *= 2;
+              break;
+            case gcEuclid:
+              // y = y;
+              y *= 2; x *= 2;
+              break;
+            }
+          break;
+          }
+        case mdBandEquiarea: {
+          y = sin_auto(y) * vid.stretch;
+          break;
+          }
+        case mdSinusoidal: {
+          x *= cos_auto(y);
+          break;
+          }
+        case mdBandEquidistant: {
+          y *= vid.stretch;
+          break;
+          }
+        default: {
+          printf("unknown model\n");
           }
-        x = (dright*dright-dleft*dleft) / 4 / p;
-        y = (y>0?1:-1) * sqrt(dleft * dleft - (x-p)*(x-p) + 1e-9);
         }
-      else if(pmodel == mdBand) switch(cgclass) {
-        case gcSphere:
-          y = atanh(sin(y));
-          x *= 2; y *= 2;
-          break;
-        case gcHyperbolic:
-          y = 2 * atan(tanh(y/2));
-          x *= 2; y *= 2;
-          break;
-        case gcEuclid:
-          // y = y;
-          y *= 2; x *= 2;
-          break;
-        }
-      else if(pmodel == mdBandEquiarea) 
-        y = sin_auto(y);
-      else if(pmodel == mdSinusoidal) 
-        x *= cos_auto(y);
       ret = hpxyz(x / M_PI, y * yf / M_PI, 0);
       if(zlev_used && stereo::active()) 
         apply_depth(ret, y * zf / M_PI);

polygons.cpp

@@ -451,7 +451,7 @@ void fixMercator(bool tinf) {
   
   if(pmodel == mdSinusoidal)
     for(int i = 0; i<isize(glcoords); i++) 
-      glcoords[i][mercator_coord] /= cos(glcoords[i][1] / vid.radius * M_PI);    
+      glcoords[i][mercator_coord] /= cos(glcoords[i][1] / vid.radius * M_PI);
     
   ld hperiod = mercator_period / 2;
   
@@ -459,10 +459,12 @@ void fixMercator(bool tinf) {
   ld cmin = -vid.xcenter, cmax = vid.xres - vid.xcenter, dmin = -vid.ycenter, dmax = vid.yres - vid.ycenter;
   if(mercator_coord)
     swap(cmin, dmin), swap(cmax, dmax);
-  if(pmodel == mdSinusoidal || pmodel == mdBandEquidistant)
+  if(pmodel == mdSinusoidal)
     dmin = -vid.radius / 2, dmax = vid.radius / 2;
+  if(pmodel == mdBandEquidistant)
+    dmin = -vid.stretch * vid.radius / 2, dmax = vid.stretch * vid.radius / 2;
   if(pmodel == mdBandEquiarea)
-    dmin = -vid.radius / M_PI, dmax = vid.radius / M_PI;
+    dmin = -vid.stretch * vid.radius / M_PI, dmax = vid.stretch * vid.radius / M_PI;
 
   for(int i = 0; i<isize(glcoords); i++) {
     while(glcoords[0][mercator_coord] < hperiod) glcoords[0][mercator_coord] += mercator_period;