Normal vector length 1.

float n fast_normalize(float n p)

Description

Returns a vector in the same direction as p but with a length of 1. fast_normalize is computed as:

          p * half_rsqrt(p.x2 + p.y2 +...)

The result shall be within 8192 ulps error from the infinitely precise result of:

          if (all(p == 0.0f))
                    result = p;
          else
                    result = p /  sqrt(p.x2 + p.y2 +...);

with the following exceptions:

  1. If the sum of squares is greater than FLT_MAX then the value of the floating-point values in the result vector are undefined.

  2. If the sum of squares is less than FLT_MIN then the implementation may return back p.

  3. If the device is in 'denorms are flushed to zero' mode, individual operand elements with magnitude less than sqrt(FLT_MIN) may be flushed to zero before proceeding with the calculation.

Notes

General information about built-in geometric functions: Built-in geometric functions operate component-wise. The description is per-component. floatn is float, float2, float3, or float4 and doublen is double, double2, double3, or double4. The built-in geometric functions are implemented using the round to nearest even rounding mode.

The geometric functions can be implemented using contractions such as mad or fma.

Also see

Specification