diff --git a/basegraph.cpp b/basegraph.cpp
index 4ee3ed22..56343fa9 100644
--- a/basegraph.cpp
+++ b/basegraph.cpp
@@ -204,10 +204,12 @@ void display_data::set_projection(int ed, bool apply_models) {
   
   shaderside_projection = false;
   glhr::new_shader_projection = glhr::shader_projection::standard;
-  if(pmodel == mdDisk && !spherespecial && !(hyperbolic && vid.alpha <= -1))
-    shaderside_projection = true;
-  if(pmodel == mdBand && hyperbolic && apply_models && !inHighQual)
-    shaderside_projection = true, glhr::new_shader_projection = glhr::shader_projection::band;
+  if(vid.consider_shader_projection) {
+    if(pmodel == mdDisk && !spherespecial && !(hyperbolic && vid.alpha <= -1))
+      shaderside_projection = true;
+    if(pmodel == mdBand && hyperbolic && apply_models && !inHighQual)
+      shaderside_projection = true, glhr::new_shader_projection = glhr::shader_projection::band;
+    }
   
   start_projection(ed, shaderside_projection);
 
diff --git a/config.cpp b/config.cpp
index cffc19d5..2452fe37 100644
--- a/config.cpp
+++ b/config.cpp
@@ -325,6 +325,8 @@ void initConfig() {
   addsaver(conformal::formula, "formula");
   addsaverenum(conformal::basic_model, "basic model");
 
+  addsaver(vid.consider_shader_projection, "shader-projection", true);
+
 #if CAP_SHMUP  
   shmup::initConfig();
 #endif
diff --git a/conformal.cpp b/conformal.cpp
index 56805637..d284c707 100644
--- a/conformal.cpp
+++ b/conformal.cpp
@@ -836,6 +836,11 @@ namespace conformal {
 
     dialog::addSelItem(XLAT("vertical stretch"), fts3(vid.stretch), 's');
 
+    dialog::addBoolItem(XLAT("use GPU to compute projections"), vid.consider_shader_projection, 'G');
+    if(vid.consider_shader_projection && !shaderside_projection)
+      dialog::lastItem().value = XLAT("N/A");
+    dialog::add_action([] { vid.consider_shader_projection = !vid.consider_shader_projection; });
+
     menuitem_sightrange('R');
       
     dialog::addBreak(100);
diff --git a/hyper.h b/hyper.h
index 19140255..1da74171 100644
--- a/hyper.h
+++ b/hyper.h
@@ -1056,6 +1056,7 @@ struct videopar {
   ld ipd;
   ld lr_eyewidth, anaglyph_eyewidth;
   ld fov;
+  bool consider_shader_projection;
   };
 
 extern videopar vid;
diff --git a/polygons.cpp b/polygons.cpp
index 146c8655..82f4c3f6 100644
--- a/polygons.cpp
+++ b/polygons.cpp
@@ -475,7 +475,7 @@ void glapplymatrix(const transmatrix& V) {
     }
   mat[12] = 0;
   mat[13] = 0;
-  mat[14] = GLfloat(vid.alpha);
+  mat[14] = (glhr::current_shader_projection == glhr::shader_projection::standard) ? GLfloat(vid.alpha) : 0;
   mat[15] = 1;  
   
   if(vid.stretch != 1) mat[1] *= vid.stretch, mat[5] *= vid.stretch, mat[9] *= vid.stretch, mat[13] *= vid.stretch;
diff --git a/shaders.cpp b/shaders.cpp
index 2568eaf0..03cc4cdb 100644
--- a/shaders.cpp
+++ b/shaders.cpp
@@ -521,6 +521,10 @@ void init() {
       1,       "  return log(sqrt(1.0 + x*x) + x);",
       1,       "  }",
       
+      1,       "float zlevel(vec4 h) {",
+      1,       "  return (h[2] < 0.0 ? -1.0 : 1.0) * sqrt(h[2]*h[2] - h[0]*h[0] - h[1]*h[1]);",
+      1,       "  }",
+
       1,       "void main() {",  
       texture,   "vTexCoord = aTexture;",
       varcol,    "vColor = aColor;",
@@ -529,6 +533,10 @@ void init() {
       !mps,      "gl_Position = uMVP * aPosition;",
       mps&&!band,"gl_Position = uP * (uMV * aPosition);",
       band,      "vec4 t = uMV * aPosition;",
+  
+      band,      "float zlev = zlevel(t);",
+      band,      "t /= zlev;",
+
       band,      "float ty = asinh(t.y);",
       band,      "float tx = asinh(t.x / cosh(ty));",
       band,      "ty = 2.0 * atan(tanh(ty/2.0));",