Alright, I think we all know about single casting, initiating one genjutsu technique at a time on one or more opponents. This is basic, but in order to cast any sort of genjutsu you need to first understand the requirments. You must have some means of knowing the location of your opponent in order to cast them under genjutsu. Primarily this means you need to have a clear line of sight, however there are other ways to be aware of your opponent's location as opposed to just sight.
Chakra sensing: sense the chakra sense the location. This is perhaps the second best way to be certian of your opponent's location.
Dojutsu: By this I primarily mean the Byakugan. You can't blind these mofos except in a few different ways. Obstructing the immediate line of vision cannot stop them from seeing/sensing you and therefore, are perhaps have the strongest way to cast genjutsu on people at any given point.
Hearing: Only when you have strong enough hearing like inner sonar. I mean any normal person can hear else where but if my sound knowledge is correct, inner sonar allows for you to hear in such great detail, possibly the even the heart beat in your opponent. This level of hearing is more than enough to figure out the location of your opponent, enough to cast them under an illusion.
Olfactory: I think this would pertain to Inuzuka bios, strong enough sense of smell to sniff out an opponent. Kiba could detect Sasuke's scent when he was some km away. In direct combat in close and mid range a high level Inuzuka should be able to sniff you out and use genjutsu.
Touch: Vibrations, I believe this would pertain to certian bio abilities like Minato's and Tobirama that for that ability to detect their opponent's through feeling the vibrations of the earth.
Taste: You got me on that one
____________
Most of what I said, pertains to specific bio abilities. Not everybody has sound or an Inuzuka, or sensory bio however there are a few techniques that are capable of allowing you to sense your opponent and should allow for you to cast illusions. I can think of two or three canon techniques off the top of my head.
List me some canon techniques that would aid you in sensing your opponent's wareabouts and also list any customs you might have to do so also.
Chakra sensing: sense the chakra sense the location. This is perhaps the second best way to be certian of your opponent's location.
Dojutsu: By this I primarily mean the Byakugan. You can't blind these mofos except in a few different ways. Obstructing the immediate line of vision cannot stop them from seeing/sensing you and therefore, are perhaps have the strongest way to cast genjutsu on people at any given point.
Hearing: Only when you have strong enough hearing like inner sonar. I mean any normal person can hear else where but if my sound knowledge is correct, inner sonar allows for you to hear in such great detail, possibly the even the heart beat in your opponent. This level of hearing is more than enough to figure out the location of your opponent, enough to cast them under an illusion.
Olfactory: I think this would pertain to Inuzuka bios, strong enough sense of smell to sniff out an opponent. Kiba could detect Sasuke's scent when he was some km away. In direct combat in close and mid range a high level Inuzuka should be able to sniff you out and use genjutsu.
Touch: Vibrations, I believe this would pertain to certian bio abilities like Minato's and Tobirama that for that ability to detect their opponent's through feeling the vibrations of the earth.
Taste: You got me on that one
____________
Most of what I said, pertains to specific bio abilities. Not everybody has sound or an Inuzuka, or sensory bio however there are a few techniques that are capable of allowing you to sense your opponent and should allow for you to cast illusions. I can think of two or three canon techniques off the top of my head.
List me some canon techniques that would aid you in sensing your opponent's wareabouts and also list any customs you might have to do so also.