very minor

openglcanvas.cpp

@@ -505,7 +505,6 @@ void OpenGLCanvas::vertex_transformation(float *positions, int m, int n, float c
                 positions[3*(j+i*n)+2] = z;
             }
 
-            // perspective
             if (visualization=="Zorin-Barr"){
                 // perspective
                 u = x/(-z);

shaders/vertex_shader.vert

@@ -71,8 +71,8 @@ void main(void){
     else if (vis_mode==3.0) // Equi-Rectangular
         gl_Position = vec4(lambda,phi,z,1.0);
     else if (vis_mode==4.0) { // Stereographic
-        u = 2.f*x/(-z+1);
-        v = 2.f*y/(-z+1);
+        u = 2.0*x/(-z+1.0);
+        v = 2.0*y/(-z+1.0);
         gl_Position = vec4(u/extent,v/extent,z,1.0);
     }
     else if (vis_mode==5.0) { // Mercator