diff --git a/drawing.cpp b/drawing.cpp
index 0992c79a..1fe89f5a 100644
--- a/drawing.cpp
+++ b/drawing.cpp
@@ -353,10 +353,9 @@ EX int get_side(const hyperpoint& H) {
     }
   if(pmodel == mdRotatedHyperboles)
     return H[1] > 0 ? -1 : 1;
-  if(pmodel == mdHyperboloid && hyperbolic)
-    return (models::sin_ball * H[2] > -models::cos_ball * H[1]) ? -1 : 1;
-  if(pmodel == mdHyperboloid && sphere)
-    return (models::sin_ball * H[2] > models::cos_ball * H[1]) ? -1 : 1;
+  if(pmodel == mdHyperboloid) {
+    return det2(pconf.ball() * cspin90(1, 2) * rgpushxto0(H)) > 0 ? 1 : -1;
+    }
   if(pmodel == mdHyperboloidFlat && sphere)
     return H[2] >= 0 ? 1 : -1;
   if(pmodel == mdHemisphere && hyperbolic) {
@@ -369,8 +368,9 @@ EX int get_side(const hyperpoint& H) {
     int s = H1[2] > 0 ? 1 : -1;
     if(hemi_side && s != hemi_side) return -spherespecial;
     H1[0] /= H1[2]; H1[1] /= H1[2];
-    H1[2] = s * sqrt(1 + H1[0]*H1[0] + H1[1] * H1[1]);
-    return (models::sin_ball * H1[2] > models::cos_ball * H1[1]) ? 1 : -1;
+    H1[2] = -s * sqrt(1 + H1[0]*H1[0] + H1[1] * H1[1]);
+    dynamicval<geometryinfo1> g(cginf.g, giHyperb2);
+    return det2(pconf.ball() * cspin90(1, 2) * rgpushxto0(H1)) > 0 ? 1 : -1;
     }
   if(pmodel == mdSpiral && pconf.spiral_cone < 360) {    
     return cone_side(shiftless(H));
@@ -2435,14 +2435,14 @@ EX void draw_main() {
     }
 
   if(pmodel == mdHemisphere && sphere && hemi_side == 0 && !vrhr::rendering()) {
-    hemi_side = models::sin_ball > 0 ? 1 : -1;
+    hemi_side = (pconf.ball() * hyperpoint(0,1,0,1)) [2] < 0 ? 1 : -1;
     draw_main();
 
     if(pconf.show_hyperboloid_flat) {
       dynamicval<eModel> dv (pmodel, mdHyperboloidFlat);
       dynamicval<int> ds (spherespecial, 1);
       for(auto& ptd: ptds)
-        if(!among(ptd->prio, PPR::MOBILE_ARROW, PPR::OUTCIRCLE, PPR::CIRCLE))
+        if(!among(ptd->prio, PPR::MOBILE_ARROW, PPR::OUTCIRCLE, PPR::CIRCLE)) 
           ptd->draw();
       }
 
diff --git a/hypgraph.cpp b/hypgraph.cpp
index 7b1b0b5c..fd2ccbad 100644
--- a/hypgraph.cpp
+++ b/hypgraph.cpp
@@ -162,7 +162,7 @@ void ballmodel(hyperpoint& ret, double alpha, double d, double zl) {
   ret[1] = ay;
   ret[2] = ax * sa;
   
-  models::apply_ball(ret[2], ret[1]);
+  ret = pconf.ball() * ret;
   }
 
 bool use_z_coordinate() {
@@ -970,7 +970,7 @@ EX void apply_other_model(shiftpoint H_orig, hyperpoint& ret, eModel md) {
       
       swap(ret[1], ret[2]);
       
-      models::apply_ball(ret[2], ret[1]);
+      ret = pconf.ball() * ret;
       
       break;
       }
@@ -1032,7 +1032,7 @@ EX void apply_other_model(shiftpoint H_orig, hyperpoint& ret, eModel md) {
       ret[0] = ret[0] / 3;
       tie(ret[1], ret[2]) = make_pair(((sphere?0:1) - ret[2]) / 3, ret[1] / 3);
       
-      models::apply_ball(ret[2], ret[1]);
+      ret = pconf.ball() * ret;
       break;
       }
     
@@ -1443,7 +1443,7 @@ EX void apply_other_model(shiftpoint H_orig, hyperpoint& ret, eModel md) {
         if(euclid) ret = models::euclidean_spin * ret;
         ret[2] = (r-1) * sqrt( pow(360/pconf.spiral_cone, 2) - 1);
         
-        models::apply_ball(ret[2], ret[1]);
+        ret = pconf.ball() * ret;
         }
       else {      
         z = exp(z);
@@ -2614,8 +2614,8 @@ EX void draw_model_elements() {
         ld z = acosh(tz);
     
         hyperpoint a = xpush0(z);
-        ld cb = models::cos_ball;
-        ld sb = models::sin_ball;
+        ld cb = pconf.ball() [1][1];
+        ld sb = pconf.ball() [1][2];
         
         a[1] = sb * a[2] / -cb;
         a[0] = sqrt(-1 + a[2] * a[2] - a[1] * a[1]);
@@ -2807,11 +2807,13 @@ EX void draw_boundary(int w) {
       break;
     
     case mdHemisphere: {
+      ld cb = pconf.ball() [1][1];
+      ld sb = pconf.ball() [2][1];
       if(hyperbolic) {
         queuereset(mdPixel, p);
         for(int i=0; i<=360; i++) {
           ld s = sin(i * degree);
-          curvepoint(point3(current_display->radius * cos(i * degree), current_display->radius * s * (models::cos_ball * s >= 0 - 1e-6 ? 1 : abs(models::sin_ball)), 0));
+          curvepoint(point3(current_display->radius * cos(i * degree), current_display->radius * s * (cb * s >= 0 - 1e-6 ? 1 : abs(sb)), 0));
           }
         queuecurve(shiftless(Id), lc, fc, p);
         queuereset(pmodel, p);
@@ -2820,7 +2822,7 @@ EX void draw_boundary(int w) {
   
         for(int i=0; i<=360; i++) {
           ld s = sin(i * degree);
-          curvepoint(point3(current_display->radius * cos(i * degree), current_display->radius * s * models::sin_ball, 0));
+          curvepoint(point3(current_display->radius * cos(i * degree), current_display->radius * s * sb, 0));
           }
         queuecurve(shiftless(Id), lc, fc, p);
         queuereset(pmodel, p);
@@ -2842,8 +2844,8 @@ EX void draw_boundary(int w) {
         as_hyperboloid:
         ld& tz = pconf.top_z;
         ld mz = sphere ? atan(sqrt(tz*tz-1)) : acosh(tz);
-        ld cb = models::cos_ball;
-        ld sb = models::sin_ball;
+        ld cb = pconf.ball() [1][1];
+        ld sb = pconf.ball() [2][1];
         
         if(abs(sb) <= abs(cb) + 1e-5) {
           ld step = .01 / (1 << vid.linequality);        
@@ -3196,7 +3198,7 @@ EX int cone_side(const shiftpoint H) {
     ret[1] = cos(alpha) * r;
     ret[2] = (r-1) * sqrt( pow(360/pconf.spiral_cone, 2) - 1);
     
-    models::apply_ball(ret[2], ret[1]);
+    ret = pconf.ball() * ret;
     return ret;
     };
   
diff --git a/legacy.cpp b/legacy.cpp
index 0ff24cb8..334e58b6 100644
--- a/legacy.cpp
+++ b/legacy.cpp
@@ -358,6 +358,11 @@ int read_legacy_args() {
     PHASE(3);  start_game();
     View = Id; playermoved = false;
     }
+  else if(argis("-ballangle")) {
+    PHASEFROM(2);
+    shift(); println(hlog, "-ballangle not implemented");
+    // shift_arg_formula(vpconf.ballangle);
+    }
   else return 1;
   return 0;
   }
diff --git a/models.cpp b/models.cpp
index 25a6bc97..1904ab47 100644
--- a/models.cpp
+++ b/models.cpp
@@ -136,6 +136,8 @@ projection_configuration::projection_configuration() {
   dualfocus_autoscale = false;
   axial_angle = 90;
   ptr_model_orientation = new trans23;
+  ptr_ball = new transmatrix;
+  *ptr_ball = cspin(1, 2, 20._deg);
   }
 
 EX namespace models {
@@ -144,7 +146,6 @@ EX namespace models {
   EX ld rotation_xz = 90;
   EX ld rotation_xy2 = 90;
   EX int do_rotate = 1;
-  EX ld cos_ball, sin_ball;
   EX bool model_straight, model_straight_yz;
 
   /** screen coordinates to orientation logical coordinates */
@@ -155,11 +156,6 @@ EX namespace models {
   EX void scr_to_ori(hyperpoint& h) { if(!model_straight) h = iso_inverse(pconf.mori().get()) * h; }
   EX void scr_to_ori(transmatrix& h) { if(!model_straight) h = iso_inverse(pconf.mori().get()) * h; }
 
-  #if HDR
-  template<class A>
-  void apply_ball(A& x, A& y) { tie(x,y) = make_pair(x*cos_ball + y*sin_ball, y*cos_ball - x*sin_ball); }
-  #endif
-
   EX transmatrix rotmatrix() {
     if(GDIM == 2 || gproduct) return spin(rotation * degree);
     return spin(rotation_xy2 * degree) * cspin(0, 2, -rotation_xz * degree) * spin(rotation * degree);
@@ -175,8 +171,6 @@ EX namespace models {
   EX transmatrix euclidean_spin;
   
   EX void configure() {
-    ld ball = -pconf.ballangle * degree;
-    cos_ball = cos(ball), sin_ball = sin(ball);
     model_straight = (pconf.mori().get()[0][0] > 1 - 1e-9);
     model_straight_yz = GDIM == 2 || (pconf.mori().get()[2][2] > 1-1e-9);
     if(history::on) history::apply();
@@ -603,7 +597,7 @@ EX namespace models {
       }
     
     if(is_3d(vpconf) && GDIM == 2 && !vr_settings) 
-      add_edit(vpconf.ballangle);     
+      add_edit(vpconf.ball());
     
     if(vr_settings) {
       dialog::addSelItem(XLAT("VR: rotate the 3D model"), fts(vpconf.vr_angle) + "°", 'B');
@@ -848,10 +842,6 @@ EX namespace models {
         shift(); vpconf.formula = args();
         }
       }
-    else if(argis("-ballangle")) { 
-      PHASEFROM(2); 
-      shift_arg_formula(vpconf.ballangle);
-      }
     else if(argis("-topz")) { 
       PHASEFROM(2); 
       shift_arg_formula(vpconf.top_z);
@@ -1099,16 +1089,15 @@ EX namespace models {
       param_f(p.camera_angle, pp+"cameraangle", sp+"camera angle", 0);
       addsaver(p.ballproj, sp+"ballproj", 1);      
 
-      param_f(p.ballangle, pp+"ballangle", sp+"ball angle", 20)
-      -> editable(0, 90, 5, "camera rotation in 3D models", 
+      param_matrix(p.ball(), pp+"ballangle", 3)
+      -> editable("camera rotation in 3D models",
         "Rotate the camera in 3D models (ball model, hyperboloid, and hemisphere). "
         "Note that hyperboloid and hemisphere models are also available in the "
         "Hypersian Rug surfaces menu, but they are rendered differently there -- "
         "by making a flat picture first, then mapping it to a surface. "
         "This makes the output better in some ways, but 3D effects are lost. "
         "Hypersian Rug model also allows more camera freedom.",
-        'b')
-      -> unit = "°";
+        'b');
 
       string help =
         "This parameter has a bit different scale depending on the settings:\n"