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[simd] Add some comments to mat4fquat

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Having to refigure out what values are going into the vectors got old
very fast. The comments don't help with verifying the values, but at
least I can tell at a glance where 2(xy - wz) goes and thus determine
the "orientation" of the matrix.
This commit is contained in:
Bill Currie 2022-05-04 13:48:34 +09:00
parent fe891dd70b
commit ef6e4722d5
1 changed files with 3 additions and 1 deletions
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4
include/QF/simd/mat4f.h
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@ -175,7 +175,7 @@ mat4fquat (mat4f_t m, vec4f_t q)
vec4f_t b = _mm_xor_ps (shuff103 (yq), (__m128) mpm);
vec4f_t c = _mm_xor_ps (shuff230 (zq), (__m128) pmm);
vec4f_t d = _mm_xor_ps (shuff321 (wq), (__m128) mmp);
// column: ww + xx - yy - zz // 2xy + 2wz // 2zx - 2wy // 0
m[0] = _mm_and_ps (a + b - c - d, (__m128) mask);
}
{
@ -183,6 +183,7 @@ mat4fquat (mat4f_t m, vec4f_t q)
vec4f_t b = yq;
vec4f_t c = _mm_xor_ps (shuff321 (zq), (__m128) mmp);
vec4f_t d = _mm_xor_ps (shuff230 (wq), (__m128) pmm);
// column: 2xy - 2wz // ww - xx + yy - zz // 2yz + 2wx // 0
m[1] = _mm_and_ps (b + c - a - d, (__m128) mask);
}
{
@ -190,6 +191,7 @@ mat4fquat (mat4f_t m, vec4f_t q)
vec4f_t b = _mm_xor_ps (shuff321 (yq), (__m128) mmp);
vec4f_t c = zq;
vec4f_t d = _mm_xor_ps (shuff103 (wq), (__m128) mpm);
// column: 2xz + 2wy // 2yz - 2wx // ww - xx - yy + zz // 0
m[2] = _mm_and_ps (a - b + c - d, (__m128) mask);
}
m[3] = (vec4f_t) { 0, 0, 0, 1 };