[Gambas-user] more trigonometry fun (not)

[Kevin Fishburne]

I was already helped graciously in figuring out how to translate a point 
in a plane along its local axes at a given orientation, but now need a 
bit of the inverse of the equation.

I need to know the (x, y) offset of a point at a given orientation and 
velocity. For example if a point is moving at an angle of 45 degrees (or 
radians, take your pick), what would its x and y coordinate be 
increased/decreased by? The variables I can think of would be:

x1 (point's current x coordinate)
y1 (point's current y coordinate)
a (point's angle/orientation in degrees/radians)
v (point's velocity)
x2 (x coordinate offset of point's new position)
y2 (y coordinate offset of point's new position)

The calculation would take x1, y1 a and v as inputs and produce x2 and 
y2 as offsets (x1 + x2, y1 + y2 = point's new position).

There really should be a list of basic things like this for graphics 
programmers. I've searched for years and found practically nothing. 
Weird, considering this has probably been done thousands of times since 
the days of DOS. :/

In case anyone's wondering why I need this, the equation will allow 
particles and projectiles to follow logical paths. Currently they're 
bound to local coordinates and ignore player orientation. Digging, 
shooting arrows, throwing objects, etc. can't work without it.

-- 
Kevin Fishburne
Eight Virtues
www: http://sales.eightvirtues.com
e-mail: sales at ...1887...
phone: (770) 853-6271