gistfile1.txt

rtDeclareVariable( float4, sphere, , ); 
rtDeclareVariable( optix::Ray, ray, rtCurrentRay, ); 
rtDeclareVariable( float3, normal, attribute normal );

RT_PROGRAM void intersect_sphere( int prim_index ) {
  float3 center = make_float3( sphere.x, sphere.y, sphere.z );
  float radius = sphere.w;
  float3 O = ray.origin - center;
  float b = dot( O, ray.direction ); float c = dot( O, O ) - radius*radius; float disc = b*b - c;
  if( disc > 0.0f ) {
    float sdisc = sqrtf( disc );
    float root1 = (-b - sdisc);
    bool check_second = true;
    if( rtPotentialIntersection( root1 ) ) {
      shading_normal = geometric_normal = (O + root1*D) / radius;
      if( rtReportIntersection( 0 ) ) check_second = false;
    }
    if( check_second ) {
      float root2 = (-b + sdisc);
      if( rtPotentialIntersection( root2 ) ) {
        shading_normal = geometric_normal = (O + root2*D) / radius;
        rtReportIntersection( 0 ); 
      }
    }
  }
}