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Diffstat (limited to 'core/ambidefs.h')
| -rw-r--r-- | core/ambidefs.h | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/core/ambidefs.h b/core/ambidefs.h index 80383450..001edc5b 100644 --- a/core/ambidefs.h +++ b/core/ambidefs.h @@ -5,6 +5,9 @@ #include <stddef.h> #include <stdint.h> +#include "alnumbers.h" + + using uint = unsigned int; /* The maximum number of Ambisonics channels. For a given order (o), the size @@ -196,4 +199,56 @@ struct AmbiIndex { } }; + +/** + * Calculates ambisonic encoder coefficients using the X, Y, and Z direction + * components, which must represent a normalized (unit length) vector. + * + * NOTE: The components use ambisonic coordinates. As a result: + * + * Ambisonic Y = OpenAL -X + * Ambisonic Z = OpenAL Y + * Ambisonic X = OpenAL -Z + * + * The components are ordered such that OpenAL's X, Y, and Z are the first, + * second, and third parameters respectively -- simply negate X and Z. + */ +constexpr auto CalcAmbiCoeffs(const float y, const float z, const float x) +{ + const float xx{x*x}, yy{y*y}, zz{z*z}, xy{x*y}, yz{y*z}, xz{x*z}; + + return std::array<float,MaxAmbiChannels>{{ + /* Zeroth-order */ + 1.0f, /* ACN 0 = 1 */ + /* First-order */ + al::numbers::sqrt3_v<float> * y, /* ACN 1 = sqrt(3) * Y */ + al::numbers::sqrt3_v<float> * z, /* ACN 2 = sqrt(3) * Z */ + al::numbers::sqrt3_v<float> * x, /* ACN 3 = sqrt(3) * X */ + /* Second-order */ + 3.872983346e+00f * xy, /* ACN 4 = sqrt(15) * X * Y */ + 3.872983346e+00f * yz, /* ACN 5 = sqrt(15) * Y * Z */ + 1.118033989e+00f * (3.0f*zz - 1.0f), /* ACN 6 = sqrt(5)/2 * (3*Z*Z - 1) */ + 3.872983346e+00f * xz, /* ACN 7 = sqrt(15) * X * Z */ + 1.936491673e+00f * (xx - yy), /* ACN 8 = sqrt(15)/2 * (X*X - Y*Y) */ + /* Third-order */ + 2.091650066e+00f * (y*(3.0f*xx - yy)), /* ACN 9 = sqrt(35/8) * Y * (3*X*X - Y*Y) */ + 1.024695076e+01f * (z*xy), /* ACN 10 = sqrt(105) * Z * X * Y */ + 1.620185175e+00f * (y*(5.0f*zz - 1.0f)), /* ACN 11 = sqrt(21/8) * Y * (5*Z*Z - 1) */ + 1.322875656e+00f * (z*(5.0f*zz - 3.0f)), /* ACN 12 = sqrt(7)/2 * Z * (5*Z*Z - 3) */ + 1.620185175e+00f * (x*(5.0f*zz - 1.0f)), /* ACN 13 = sqrt(21/8) * X * (5*Z*Z - 1) */ + 5.123475383e+00f * (z*(xx - yy)), /* ACN 14 = sqrt(105)/2 * Z * (X*X - Y*Y) */ + 2.091650066e+00f * (x*(xx - 3.0f*yy)), /* ACN 15 = sqrt(35/8) * X * (X*X - 3*Y*Y) */ + /* Fourth-order */ + /* ACN 16 = sqrt(35)*3/2 * X * Y * (X*X - Y*Y) */ + /* ACN 17 = sqrt(35/2)*3/2 * (3*X*X - Y*Y) * Y * Z */ + /* ACN 18 = sqrt(5)*3/2 * X * Y * (7*Z*Z - 1) */ + /* ACN 19 = sqrt(5/2)*3/2 * Y * Z * (7*Z*Z - 3) */ + /* ACN 20 = 3/8 * (35*Z*Z*Z*Z - 30*Z*Z + 3) */ + /* ACN 21 = sqrt(5/2)*3/2 * X * Z * (7*Z*Z - 3) */ + /* ACN 22 = sqrt(5)*3/4 * (X*X - Y*Y) * (7*Z*Z - 1) */ + /* ACN 23 = sqrt(35/2)*3/2 * (X*X - 3*Y*Y) * X * Z */ + /* ACN 24 = sqrt(35)*3/8 * (X*X*X*X - 6*X*X*Y*Y + Y*Y*Y*Y) */ + }}; +} + #endif /* CORE_AMBIDEFS_H */ |