### math

#### Find any point on arc given center, start point, end point, total angle, normal, and radius

```I have an 3D arc with coordinates such as:
start = (-3,6,12)
end = (-13,11,12)
center = (-9,6,14)
norm = (0.3204,0.6304,0.7071)
Along with angle information:
start angle = 216
total angle = 108
end angle = 324
Using the given information, I want to interpolate the arc at a specified distance. To do this, I perform the same operation in a loop and increment or decremented the angle depending on the direction I choose (start to end or vice-versa).
I figured out how to do so in 2D with the algorithm:
X = r * cosine(angle)
Y = r * sine(angle)
X = Cx + (r * cosine(angle))
Y = Cy + (r * sine(angle))
But once I add the Z axis it gets very confusing. I have been looking at multiple methods that use operations such as the cross product but these make me even more confused.
How should I proceed with this?
```
```If center is center of circle, than you have almost all information needed for SLERP - spherical linear interpolation
p0 = start - circlecenter
p1 = end - circlecenter
p(t) = p0 * Sin(W*(1-t)) / Sin(W) + p1 * Sin(W*t) / Sin(W)
point(t) = circlecenter + p(t)
where p0 and p1 are starting and ending radius-vectors, W is total angle, t is
parameter in range 0..1 (so W*t lies in range 0..total angle)
If your center is middle of arc, you can find circle center:
chord = end - start
uchord = chord.normalize //(unit vector)
perp = VectorProduct(normal, uchord) //unit vector in circle plane
circlecenter = middle + perp * radius```

### Resources

Mobile Apps Dev
Database Users
javascript
java
csharp
php
android
MS Developer
developer works
python
ios
c
html
jquery
RDBMS discuss
Cloud Virtualization