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DarkBASIC Discussion / direction and range detection

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RCON
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Posted: 8th May 2003 00:16
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Is there a function or formula that will check a object with another and return the angle or range to that object?
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Hamish McHaggis
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Posted: 8th May 2003 00:44 Edited at: 8th May 2003 00:45
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To find the angle, I guess you have to use trig. Try this formula...

x_dif#=object position x(obj1)-object position x(obj2)
z_dif#=object position z(obj1)-object position z(obj2)
y_angle#=atan(x_dif#/z_dif#)

To find the distance between the objects you use pythagorus' theorum...

ON 2 DIMENSIONS (a plane)
z^2 = y^2+x^2
or
z = sqrt(y^2+x^2)

ON 3 DIMENSIONS
z^2 = y^2+x^2+w^2
or
z = sqrt(y^2+x^2+w^2)

where...
z = the dist between the two points
w, x and y = the difference (distance) between the x,y and z coordinates of the objects.

Why the hell'd you ask me for crying out loud!?!

Athelon XP 1400 Plus - Nvidia Geforce MX400 - 256mb RAM
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RCON
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Posted: 8th May 2003 01:59
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so it would look like this:

rem get object position differences
x_dif#=object position x(recognizer)-object position x(200)
z_dif#=object position z(recognizer)-object position z(200)

rem angle difference
y_angle#=atan(x_dif#/z_dif#)

rem distance range
z = sqrt(x_dif#^2+z_dif#^2)

(i can't test it until I get home, just wanted to see if this is right.) BTW its a 3d game, but I don't really use elevation.
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Hell IVIonkey
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Posted: 8th May 2003 03:07
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You're best off using the distance squared formula and skipping the middle steps:

dist_squared = (x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2

Then when you do a test to say if an object less than value away, use the form:

if (value)^2 < dist_squared then do whatever.

Why? Square roots are slow when done in bulk.
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RCON
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Posted: 8th May 2003 19:23
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ok I have range working good, but I have a question on the angle. I have to admit that I am pretty bad with math, and I want the angle that is returned to be a 0-360 degree number. the angle that I can get returned now is a number between -90 - 0 - 90. for example, if my "hunter" object sees the "hunted" object at -45, the hunted could either be front left or back right to the hunter. So my hunter doesn't know the correct direction to turn to track the hunted object.
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Hamish McHaggis
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Posted: 8th May 2003 19:37
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I think the formula atan(x_diff#/z_diff#) will find that angle for you.

Why the hell'd you ask me for crying out loud!?!

Athelon XP 1400 Plus - Nvidia Geforce MX400 - 256mb RAM
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RCON
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Posted: 8th May 2003 20:16
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it does return an angle, but its in the -90 to 90 range, and it would help me a lot if it returned an angle in the 0 to 359 range.
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Hamish McHaggis
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Posted: 8th May 2003 21:23
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Try

asin(x_dist#/dist_range#)

or

acos(y_dist#/dist_range#)

Possibly

Why the hell'd you ask me for crying out loud!?!

Athelon XP 1400 Plus - Nvidia Geforce MX400 - 256mb RAM
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Danmatsuma
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Posted: 8th May 2003 22:32 Edited at: 8th May 2003 23:10
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You want a 360 degree angle between 2 objects?

angle#=wrapvalue(atanfull(x_diff#,z_diff#))



ZX Spectrum 48k Issue 3, Radio shack Tape drive, Rank arena 12" T.V. set.
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Hamish McHaggis
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Posted: 8th May 2003 23:33
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Ahhh! atanfull, thats why it wasn't working

Why the hell'd you ask me for crying out loud!?!

Athelon XP 1400 Plus - Nvidia Geforce MX400 - 256mb RAM
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RCON
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Posted: 9th May 2003 07:08
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you guys rock!
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