# simd_incircle Tests if a single-precision point lies inside, on, or outside a circle. ``` static float simd_incircle(simd_float2 __x, simd_float2 __a, simd_float2 __b, simd_float2 __c); ``` ## Parameters `__x` The point that the function tests. `__a` The first point that determines the circle. `__b` The second point that determines the circle. `__c` The third point that determines the circle. ## Return Value A value that indicates whether the point lies inside, on, or outside the specified circle. ## Discussion If the points `a`, `b`, and `c` describe a positively- or counterclockwise-oriented circle, the function returns: - A positive value if `x` is inside the circle - Zero if `x` is on the circle - A negative value if `x` is outside the circle The function flips sign of the return value if the circle is negatively- or clockwise-oriented. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)