Math: vertical viewing angle

[hiddos]

An alternative way of doing both of these together is through some vector calculations. You want to essentially do step 3 of the image below:




Some rough code (that I didn't test for accuracy) would look like:

PHP Code:

new?Float:xn,?Float:yn,?Float:zn;
FCNPC_GetPosition(npcid,?xn,?yn,?zn);

//?Get?player?position
new?Float:xp,?Float:yp,?Float:zp;
if(!IsPlayerNPC(playerid))?{
?? GetPlayerPos(playerid,?xp,?yp,?zp);
}?else?{
??? FCNPC_GetPosition(playerid,?xp,?yp,?zp);
}

// First the vector from the NPC to the player
Float:vector_diff[3] = {xp-xn, yp-yn, zp-zn};


Float:facing_angle = FCNPC_GetAngle(npcid)  90; // add 90 degrees to align with unit circle
// Then a unit vector for the angle the NPC is facing - nb. norm of this vector does not matter, but for unit vectors it's 1
Float:vector_facing[3] = {floatcos(facing_angle), floatsin(facing_angle), 0.0f};

// Calculate the dot product, to get the numerator: 
Float:dot_product = vector_diff[0] * vector_facing[0]  
???????? ? ? ? ? ?? vector_diff[1] * vector_facing[1]  
?????????? ? ? ? ?? vector_diff[2] * vector_facing[2];

// Calculate the denominator
Float:normcalc = VectorSize(vector_diff[0], vector_diff[1], vector_diff[2]); // VectorSize(vector_facing) = 1, so multiplication is not needed in this special case

//Then this is the angle between the facing angle and the?player
Float:angle = acos(dot_product/normcalc);

return angle <= max_viewing_angle; // Insert your own variable here