am I correct? I should be aiming in the red triangle?
Yes that is correct. Aim for the center of that triangle and you will be aiming at the perfect spot to hit a big boar. Any decent boar you kill be it rifle or dogs, look and familiarize yourself with the lightly skinned unprotected crease at the bottom of the shoulder right where your red triangle is. It's really exposed well when that leg is forward. In a perfect world that's when you should shoot for it but even if an animal comes in and settles at a feeder and feeds for 15 minutes, it might always be facing you and rarely offer the perfect shot. Some animals come in and just prefer to face broad side 90% of the time which is perfect. Just do the best you can but remember to not grip the bow because you will be excited. Gripping the bow buts torque in it and will cause your arrow not to hit where you do in practice. Aim for the center of that triangle and not just the triangle the self (aim small miss small) stay relaxed and don't grab the bow at the shot, just let it fall forward in your hand as in practice. Before you shoot make dang sure all your anchor points are in place. Knuckle to the ear lobe, string touching the tip of your nose, and the pin sight centered perfectly in the peep. I mention all this because it is a small area you are aiming for and you won't hit it unless your shot is perfect.
If your shooting from an elated position, then you will need to aim at the top of that red triangle do to the trajectory of the arrow when it smacks him right there. To steep of an angle and you won't hit vitals aiming that low, your will just graze him so to speak. I'm normally on the ground when I'm whacking pigs and that's my shot. Remember that most of their good vitals are further forward than a deer and are below the midway portion of a pig at its shoulders. I dont shoot any farther back than tight behind the shoulder because i want lung at a minimum, not liver. In my perfect world, i want to enter tight behind the near shoulder and try to break the leg on the of side shoulder. When ever you do stick your pigs with an arrow you think is a great shot, open it up carefully and examine what the arrow pierced with the animal laying flat on its side, not hanging. I've gone so far as to totally remove the shoulder and rib cage to the diafram to look at how the vitals layed in there and how they were protected. I studied how i wanted my arrows to penitrate because I sought huge boar with a bow and they are soooo heavily and well protected.