#pragma glslify: gnom_t = require('./t.glsl')
#pragma glslify: adjust_lon = require('../lib/adjust_lon.glsl')

const float EPSILON = 1.0e-10;
const float PI = 3.141592653589793;

vec3 gnom_forward (gnom_t t, vec3 p) {
  float lon = p.x/180.0*PI, lat = p.y/180.0*PI;
  float dlon = adjust_lon(lon - t.lon0);
  float sinphi = sin(lat);
  float cosphi = cos(lat);
  float coslon = cos(dlon);
  float g = t.sin_p14 * sinphi + t.cos_p14 * cosphi * coslon;
  float ksp = 1.0;
  if (g > 0.0 || abs(g) <= EPSILON) {
    return vec3(
      t.x0+t.k0*t.a*ksp*cosphi*sin(dlon)/g,
      t.y0+t.k0*t.a*ksp*(t.cos_p14*sinphi-t.sin_p14*cosphi*coslon)/g,
      t.z0+t.k0*p.z
    );
  } else {
    return vec3(
      t.x0+t.k0*t.infinity_dist*cosphi*sin(dlon),
      t.y0+t.k0*t.infinity_dist*(t.cos_p14*sinphi-t.sin_p14*cosphi*coslon),
      t.z0+t.k0*p.z
    );
  }
}
vec3 gnom_forward (gnom_t t, vec2 p) {
  return gnom_forward(t,vec3(p,0));
}
#pragma glslify: export(gnom_forward)