indicatrix 0.8.1

A physically-based spectral gemstone renderer that turns GemCAD-style cutting instructions into rendered output.
Documentation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
// ---------------------------------------------------------------------------------
// P2 full uniaxial Fresnel (Lekner 1991) -- GPU mirror of
// `optics::raytracer::uniaxial_fresnel` (see that module's own Rust doc comment for
// the physics/derivation; this section is a direct, op-for-op translation, the same
// convention every other section of this file already follows -- e.g. the Phase 4
// `Biaxial*` functions above). Deliberately entirely self-contained (no `Cplx`/complex
// arithmetic exists anywhere else in this shader tree) since the CPU module itself
// states explicitly why: "the WGSL mirror needs the exact same explicit re/im
// arithmetic -- a `vec2<f32>`-based complex type there, hand-written
// `add`/`mul`/`div`/`sqrt`, exactly mirrors this" (see `Cplx`'s own Rust doc comment).
// A plain two-field struct is used here instead of `vec2<f32>` purely so field access
// reads `.re`/`.im` (matching the Rust field names exactly) rather than `.x`/`.y`.
//
// Wired into `spectral_transport.wgsl`'s uniaxial entry AND internal-reflection/exit
// dispatch -- see that file's own P2-full section for the branch structure this
// mirrors (`apply_uniaxial_entry_bounce`/`apply_uniaxial_internal_bounce` on the CPU
// side), including the same `k_hat` x `c_axis` degenerate-axis guard.
//
// Verified against the CPU implementation by `renderer::gpu::transport_check`'s
// `run_entry_solve_pair`/`run_internal_solve` Tier 2 ULP checks (feeds IDENTICAL
// `(n1, n_o, n_e, c_axis, frame)` inputs to both `uniaxial_fresnel::entry_solve_pair`/
// `internal_solve` and this section's `entry_solve_pair_with_incidence`/
// `internal_solve`, compares every output field within a ULP budget) and Tier 3 image
// comparison for Zircon/Tourmaline/Quartz/Rutile.
// ---------------------------------------------------------------------------------

struct Cplx {
    re: f32,
    im: f32,
}

fn cplx_re(re: f32) -> Cplx {
    var c: Cplx;
    c.re = re;
    c.im = 0.0;
    return c;
}

fn cplx_zero() -> Cplx {
    return cplx_re(0.0);
}

fn cplx_add(a: Cplx, b: Cplx) -> Cplx {
    var c: Cplx;
    c.re = a.re + b.re;
    c.im = a.im + b.im;
    return c;
}

fn cplx_sub(a: Cplx, b: Cplx) -> Cplx {
    var c: Cplx;
    c.re = a.re - b.re;
    c.im = a.im - b.im;
    return c;
}

fn cplx_mul(a: Cplx, b: Cplx) -> Cplx {
    var c: Cplx;
    c.re = a.re * b.re - a.im * b.im;
    c.im = a.re * b.im + a.im * b.re;
    return c;
}

fn cplx_scale(a: Cplx, s: f32) -> Cplx {
    var c: Cplx;
    c.re = a.re * s;
    c.im = a.im * s;
    return c;
}

fn cplx_conj(a: Cplx) -> Cplx {
    var c: Cplx;
    c.re = a.re;
    c.im = -a.im;
    return c;
}

fn cplx_norm_sqr(a: Cplx) -> f32 {
    return fma(a.im, a.im, a.re * a.re);
}

// optics::raytracer::uniaxial_fresnel::Cplx::div
fn cplx_div(a: Cplx, b: Cplx) -> Cplx {
    let denom = max(fma(b.im, b.im, b.re * b.re), 1e-20);
    var c: Cplx;
    c.re = fma(a.im, b.im, a.re * b.re) / denom;
    c.im = fma(a.re, -b.im, a.im * b.re) / denom;
    return c;
}

// optics::raytracer::uniaxial_fresnel::Cplx::sqrt_forward_branch
fn cplx_sqrt_forward_branch(a: Cplx) -> Cplx {
    // Mirrors the CPU function's own identical fix -- see that function's doc comment
    // for the full derivation. A
    // pure negative-real input makes `theta` land exactly on `pi/2`, where
    // `cos(theta)`'s sign is rounding noise this hardware's trig unit resolves
    // differently from Rust's `atan2`/`cos`; bypassing that round-trip for this one
    // input shape makes both platforms compute the identical, contract-correct
    // (`im > 0`) result.
    if (a.im == 0.0 && a.re < 0.0) {
        var out0: Cplx;
        out0.re = 0.0;
        out0.im = sqrt(-a.re);
        return out0;
    }
    let r = sqrt(sqrt(cplx_norm_sqr(a)));
    let theta = atan2(a.im, a.re) * 0.5;
    var out: Cplx;
    out.re = r * cos(theta);
    out.im = r * sin(theta);
    if (out.re < 0.0) {
        out.re = -out.re;
        out.im = -out.im;
    }
    if (abs(out.re) < 1e-9 && out.im < 0.0) {
        out.re = -out.re;
        out.im = -out.im;
    }
    return out;
}

// optics::raytracer::uniaxial_fresnel::CVec3
struct CVec3 {
    re: vec3<f32>,
    im: vec3<f32>,
}

fn cvec3_from_real(v: vec3<f32>) -> CVec3 {
    var c: CVec3;
    c.re = v;
    c.im = vec3<f32>(0.0, 0.0, 0.0);
    return c;
}

fn cvec3_wavevector(that: vec3<f32>, zhat: vec3<f32>, tangential: f32, q: Cplx) -> CVec3 {
    var c: CVec3;
    c.re = that * tangential + zhat * q.re;
    c.im = zhat * q.im;
    return c;
}

fn cvec3_add(a: CVec3, b: CVec3) -> CVec3 {
    var c: CVec3;
    c.re = a.re + b.re;
    c.im = a.im + b.im;
    return c;
}

fn cvec3_scale_real(a: CVec3, s: f32) -> CVec3 {
    var c: CVec3;
    c.re = a.re * s;
    c.im = a.im * s;
    return c;
}

fn cvec3_scale_complex(a: CVec3, s: Cplx) -> CVec3 {
    var c: CVec3;
    c.re = a.re * s.re - a.im * s.im;
    c.im = a.re * s.im + a.im * s.re;
    return c;
}

fn cvec3_cross_real(a: CVec3, r: vec3<f32>) -> CVec3 {
    var c: CVec3;
    c.re = cross(a.re, r);
    c.im = cross(a.im, r);
    return c;
}

fn cvec3_cross(a: CVec3, b: CVec3) -> CVec3 {
    var c: CVec3;
    c.re = cross(a.re, b.re) - cross(a.im, b.im);
    c.im = cross(a.re, b.im) + cross(a.im, b.re);
    return c;
}

fn cvec3_dot_real(a: CVec3, r: vec3<f32>) -> Cplx {
    var c: Cplx;
    c.re = dot(a.re, r);
    c.im = dot(a.im, r);
    return c;
}

fn cvec3_conj(a: CVec3) -> CVec3 {
    var c: CVec3;
    c.re = a.re;
    c.im = -a.im;
    return c;
}

// optics::raytracer::uniaxial_fresnel::UniaxialFrame::build
struct UniaxialFrameW {
    that: vec3<f32>,
    zhat: vec3<f32>,
    s_axis: vec3<f32>,
    p_axis: vec3<f32>,
    cos_i: f32,
    sin_i: f32,
    alpha: f32,
    beta: f32,
    gamma: f32,
}

fn uniaxial_frame_build(k_hat: vec3<f32>, normal: vec3<f32>, c_axis: vec3<f32>, cos_i: f32, sin_i: f32) -> UniaxialFrameW {
    var f: UniaxialFrameW;
    f.zhat = -normal;
    var that: vec3<f32>;
    if (sin_i > 1e-5) {
        that = normalize_or_zero((k_hat + normal * cos_i) / sin_i);
    } else {
        var fallback: vec3<f32>;
        if (abs(f.zhat.x) < 0.9) {
            fallback = vec3<f32>(1.0, 0.0, 0.0);
        } else {
            fallback = vec3<f32>(0.0, 1.0, 0.0);
        }
        that = normalize_or_zero(fallback - f.zhat * dot(f.zhat, fallback));
    }
    f.that = that;
    var s_axis = normalize_or_zero(cross(k_hat, normal));
    if (dot(s_axis, s_axis) <= 1e-8) {
        s_axis = normalize_or_zero(cross(f.zhat, that));
    }
    f.s_axis = s_axis;
    f.p_axis = cross(k_hat, s_axis);
    f.cos_i = cos_i;
    f.sin_i = sin_i;
    f.alpha = dot(c_axis, that);
    f.beta = dot(c_axis, s_axis);
    f.gamma = dot(c_axis, f.zhat);
    return f;
}

// optics::raytracer::uniaxial_fresnel::uniaxial_q_roots
struct QRootsW {
    qo_plus: Cplx,
    qo_minus: Cplx,
    qe_plus: Cplx,
    qe_minus: Cplx,
}

fn uniaxial_q_roots(n_o: f32, n_e: f32, frame: UniaxialFrameW, tangential: f32) -> QRootsW {
    let n_o2 = n_o * n_o;
    let k2 = tangential * tangential;

    let qo2 = cplx_re(n_o2 - k2);
    let qo_plus = cplx_sqrt_forward_branch(qo2);
    let qo_minus = cplx_sub(cplx_zero(), qo_plus);

    var result: QRootsW;
    result.qo_plus = qo_plus;
    result.qo_minus = qo_minus;

    // Performance (requirement 7): exact isotropic limit, mirrors the CPU's own
    // `uniaxial_q_roots` fast path exactly -- see that function's doc comment for the
    // algebraic derivation (both extraordinary roots collapse to the ordinary ones
    // exactly at `n_o == n_e`).
    if (n_o == n_e) {
        result.qe_plus = qo_plus;
        result.qe_minus = qo_minus;
        return result;
    }

    let n_e2 = n_e * n_e;
    let deleps = n_e2 - n_o2;
    let denom = fma(frame.gamma * frame.gamma, deleps, n_o2);
    let a_term = fma(frame.beta * frame.beta, -deleps, n_e2);
    let b_term = n_e2 * fma(frame.gamma * frame.gamma, deleps, n_o2);
    let d_val = n_o2 * fma(a_term, -k2, b_term);
    let sqrt_d = cplx_sqrt_forward_branch(cplx_re(d_val));
    let shift = cplx_re(frame.alpha * frame.gamma * tangential * deleps);
    let denom_c = cplx_re(max(denom, 1e-12));
    result.qe_plus = cplx_div(cplx_sub(sqrt_d, shift), denom_c);
    result.qe_minus = cplx_div(cplx_sub(cplx_sub(cplx_zero(), sqrt_d), shift), denom_c);
    return result;
}

// optics::raytracer::uniaxial_fresnel::ModeFields / ordinary_mode_fields /
// extraordinary_mode_fields
struct ModeFieldsW {
    k: CVec3,
    e: CVec3,
    h: CVec3,
}

fn ordinary_mode_fields(n_o: f32, c_axis: vec3<f32>, that: vec3<f32>, zhat: vec3<f32>, tangential: f32, q: Cplx) -> ModeFieldsW {
    var m: ModeFieldsW;
    m.k = cvec3_wavevector(that, zhat, tangential, q);
    let d_o = cvec3_cross_real(m.k, c_axis);
    m.e = cvec3_scale_real(d_o, 1.0 / (n_o * n_o));
    m.h = cvec3_cross(m.k, m.e);
    return m;
}

fn extraordinary_mode_fields(n_o: f32, n_e: f32, c_axis: vec3<f32>, that: vec3<f32>, zhat: vec3<f32>, tangential: f32, q: Cplx) -> ModeFieldsW {
    let n_o2 = n_o * n_o;
    let n_e2 = n_e * n_e;
    let deleps = n_e2 - n_o2;
    var m: ModeFieldsW;
    m.k = cvec3_wavevector(that, zhat, tangential, q);
    let d_o = cvec3_cross_real(m.k, c_axis);
    let d_e = cvec3_cross(m.k, d_o);
    let c_dot_de = cvec3_dot_real(d_e, c_axis);
    let term1 = cvec3_scale_real(d_e, 1.0 / n_o2);
    let term2 = cvec3_scale_complex(cvec3_from_real(c_axis), cplx_scale(c_dot_de, -(deleps / (n_o2 * n_e2))));
    m.e = cvec3_add(term1, term2);
    m.h = cvec3_cross(m.k, m.e);
    return m;
}

// optics::raytracer::uniaxial_fresnel::poynting_z
fn poynting_z(fields: ModeFieldsW, amp: Cplx, zhat: vec3<f32>) -> f32 {
    let e = cvec3_scale_complex(fields.e, amp);
    let h = cvec3_scale_complex(fields.h, amp);
    let hc = cvec3_conj(h);
    let s = cvec3_cross(e, hc);
    return 0.5 * cvec3_dot_real(s, zhat).re;
}

// optics::raytracer::uniaxial_fresnel::tangential_components
fn tangential_components(fields: ModeFieldsW, that: vec3<f32>, s_axis: vec3<f32>) -> array<Cplx, 4> {
    var out: array<Cplx, 4>;
    out[0] = cvec3_dot_real(fields.e, that);
    out[1] = cvec3_dot_real(fields.e, s_axis);
    out[2] = cvec3_dot_real(fields.h, that);
    out[3] = cvec3_dot_real(fields.h, s_axis);
    return out;
}

// BEGIN GENERATED solve4 (tools/unroll_solve4.py)
// Constant-index unrolled Gauss-Jordan: same arithmetic, same order, same pivoting as
// the rolled form (strict `>`, ascending rows, whole-row conditional swap, `!= 0.0`
// factor skip). DO NOT EDIT BY HAND: regenerate with
//     python crates/indicatrix/tools/unroll_solve4.py
// (`--check` verifies this region is current.)

// optics::raytracer::uniaxial_fresnel::solve4 -- Gauss-Jordan, single RHS.
fn solve4_single(a_in: array<array<Cplx, 4>, 4>, b_in: array<Cplx, 4>) -> array<Cplx, 4> {
    var a = a_in;
    var b = b_in;
    // column 0: pivot search
    var piv0: u32 = 0u;
    var piv_mag0: f32 = cplx_norm_sqr(a[0][0]);
    let mag0_1 = cplx_norm_sqr(a[1][0]);
    if (mag0_1 > piv_mag0) {
        piv0 = 1u;
        piv_mag0 = mag0_1;
    }
    let mag0_2 = cplx_norm_sqr(a[2][0]);
    if (mag0_2 > piv_mag0) {
        piv0 = 2u;
        piv_mag0 = mag0_2;
    }
    let mag0_3 = cplx_norm_sqr(a[3][0]);
    if (mag0_3 > piv_mag0) {
        piv0 = 3u;
        piv_mag0 = mag0_3;
    }
    if (piv0 == 1u) {
        let t0_1_0 = a[0][0];
        a[0][0] = a[1][0];
        a[1][0] = t0_1_0;
        let t0_1_1 = a[0][1];
        a[0][1] = a[1][1];
        a[1][1] = t0_1_1;
        let t0_1_2 = a[0][2];
        a[0][2] = a[1][2];
        a[1][2] = t0_1_2;
        let t0_1_3 = a[0][3];
        a[0][3] = a[1][3];
        a[1][3] = t0_1_3;
        let tb0_1_b = b[0];
        b[0] = b[1];
        b[1] = tb0_1_b;
    }
    if (piv0 == 2u) {
        let t0_2_0 = a[0][0];
        a[0][0] = a[2][0];
        a[2][0] = t0_2_0;
        let t0_2_1 = a[0][1];
        a[0][1] = a[2][1];
        a[2][1] = t0_2_1;
        let t0_2_2 = a[0][2];
        a[0][2] = a[2][2];
        a[2][2] = t0_2_2;
        let t0_2_3 = a[0][3];
        a[0][3] = a[2][3];
        a[2][3] = t0_2_3;
        let tb0_2_b = b[0];
        b[0] = b[2];
        b[2] = tb0_2_b;
    }
    if (piv0 == 3u) {
        let t0_3_0 = a[0][0];
        a[0][0] = a[3][0];
        a[3][0] = t0_3_0;
        let t0_3_1 = a[0][1];
        a[0][1] = a[3][1];
        a[3][1] = t0_3_1;
        let t0_3_2 = a[0][2];
        a[0][2] = a[3][2];
        a[3][2] = t0_3_2;
        let t0_3_3 = a[0][3];
        a[0][3] = a[3][3];
        a[3][3] = t0_3_3;
        let tb0_3_b = b[0];
        b[0] = b[3];
        b[3] = tb0_3_b;
    }
    let pivot0 = a[0][0];
    a[0][0] = cplx_div(a[0][0], pivot0);
    a[0][1] = cplx_div(a[0][1], pivot0);
    a[0][2] = cplx_div(a[0][2], pivot0);
    a[0][3] = cplx_div(a[0][3], pivot0);
    b[0] = cplx_div(b[0], pivot0);
    let factor0_1 = a[1][0];
    if (cplx_norm_sqr(factor0_1) != 0.0) {
        a[1][0] = cplx_sub(a[1][0], cplx_mul(factor0_1, a[0][0]));
        a[1][1] = cplx_sub(a[1][1], cplx_mul(factor0_1, a[0][1]));
        a[1][2] = cplx_sub(a[1][2], cplx_mul(factor0_1, a[0][2]));
        a[1][3] = cplx_sub(a[1][3], cplx_mul(factor0_1, a[0][3]));
        b[1] = cplx_sub(b[1], cplx_mul(factor0_1, b[0]));
    }
    let factor0_2 = a[2][0];
    if (cplx_norm_sqr(factor0_2) != 0.0) {
        a[2][0] = cplx_sub(a[2][0], cplx_mul(factor0_2, a[0][0]));
        a[2][1] = cplx_sub(a[2][1], cplx_mul(factor0_2, a[0][1]));
        a[2][2] = cplx_sub(a[2][2], cplx_mul(factor0_2, a[0][2]));
        a[2][3] = cplx_sub(a[2][3], cplx_mul(factor0_2, a[0][3]));
        b[2] = cplx_sub(b[2], cplx_mul(factor0_2, b[0]));
    }
    let factor0_3 = a[3][0];
    if (cplx_norm_sqr(factor0_3) != 0.0) {
        a[3][0] = cplx_sub(a[3][0], cplx_mul(factor0_3, a[0][0]));
        a[3][1] = cplx_sub(a[3][1], cplx_mul(factor0_3, a[0][1]));
        a[3][2] = cplx_sub(a[3][2], cplx_mul(factor0_3, a[0][2]));
        a[3][3] = cplx_sub(a[3][3], cplx_mul(factor0_3, a[0][3]));
        b[3] = cplx_sub(b[3], cplx_mul(factor0_3, b[0]));
    }
    // column 1: pivot search
    var piv1: u32 = 1u;
    var piv_mag1: f32 = cplx_norm_sqr(a[1][1]);
    let mag1_2 = cplx_norm_sqr(a[2][1]);
    if (mag1_2 > piv_mag1) {
        piv1 = 2u;
        piv_mag1 = mag1_2;
    }
    let mag1_3 = cplx_norm_sqr(a[3][1]);
    if (mag1_3 > piv_mag1) {
        piv1 = 3u;
        piv_mag1 = mag1_3;
    }
    if (piv1 == 2u) {
        let t1_2_0 = a[1][0];
        a[1][0] = a[2][0];
        a[2][0] = t1_2_0;
        let t1_2_1 = a[1][1];
        a[1][1] = a[2][1];
        a[2][1] = t1_2_1;
        let t1_2_2 = a[1][2];
        a[1][2] = a[2][2];
        a[2][2] = t1_2_2;
        let t1_2_3 = a[1][3];
        a[1][3] = a[2][3];
        a[2][3] = t1_2_3;
        let tb1_2_b = b[1];
        b[1] = b[2];
        b[2] = tb1_2_b;
    }
    if (piv1 == 3u) {
        let t1_3_0 = a[1][0];
        a[1][0] = a[3][0];
        a[3][0] = t1_3_0;
        let t1_3_1 = a[1][1];
        a[1][1] = a[3][1];
        a[3][1] = t1_3_1;
        let t1_3_2 = a[1][2];
        a[1][2] = a[3][2];
        a[3][2] = t1_3_2;
        let t1_3_3 = a[1][3];
        a[1][3] = a[3][3];
        a[3][3] = t1_3_3;
        let tb1_3_b = b[1];
        b[1] = b[3];
        b[3] = tb1_3_b;
    }
    let pivot1 = a[1][1];
    a[1][1] = cplx_div(a[1][1], pivot1);
    a[1][2] = cplx_div(a[1][2], pivot1);
    a[1][3] = cplx_div(a[1][3], pivot1);
    b[1] = cplx_div(b[1], pivot1);
    let factor1_0 = a[0][1];
    if (cplx_norm_sqr(factor1_0) != 0.0) {
        a[0][1] = cplx_sub(a[0][1], cplx_mul(factor1_0, a[1][1]));
        a[0][2] = cplx_sub(a[0][2], cplx_mul(factor1_0, a[1][2]));
        a[0][3] = cplx_sub(a[0][3], cplx_mul(factor1_0, a[1][3]));
        b[0] = cplx_sub(b[0], cplx_mul(factor1_0, b[1]));
    }
    let factor1_2 = a[2][1];
    if (cplx_norm_sqr(factor1_2) != 0.0) {
        a[2][1] = cplx_sub(a[2][1], cplx_mul(factor1_2, a[1][1]));
        a[2][2] = cplx_sub(a[2][2], cplx_mul(factor1_2, a[1][2]));
        a[2][3] = cplx_sub(a[2][3], cplx_mul(factor1_2, a[1][3]));
        b[2] = cplx_sub(b[2], cplx_mul(factor1_2, b[1]));
    }
    let factor1_3 = a[3][1];
    if (cplx_norm_sqr(factor1_3) != 0.0) {
        a[3][1] = cplx_sub(a[3][1], cplx_mul(factor1_3, a[1][1]));
        a[3][2] = cplx_sub(a[3][2], cplx_mul(factor1_3, a[1][2]));
        a[3][3] = cplx_sub(a[3][3], cplx_mul(factor1_3, a[1][3]));
        b[3] = cplx_sub(b[3], cplx_mul(factor1_3, b[1]));
    }
    // column 2: pivot search
    var piv2: u32 = 2u;
    var piv_mag2: f32 = cplx_norm_sqr(a[2][2]);
    let mag2_3 = cplx_norm_sqr(a[3][2]);
    if (mag2_3 > piv_mag2) {
        piv2 = 3u;
        piv_mag2 = mag2_3;
    }
    if (piv2 == 3u) {
        let t2_3_0 = a[2][0];
        a[2][0] = a[3][0];
        a[3][0] = t2_3_0;
        let t2_3_1 = a[2][1];
        a[2][1] = a[3][1];
        a[3][1] = t2_3_1;
        let t2_3_2 = a[2][2];
        a[2][2] = a[3][2];
        a[3][2] = t2_3_2;
        let t2_3_3 = a[2][3];
        a[2][3] = a[3][3];
        a[3][3] = t2_3_3;
        let tb2_3_b = b[2];
        b[2] = b[3];
        b[3] = tb2_3_b;
    }
    let pivot2 = a[2][2];
    a[2][2] = cplx_div(a[2][2], pivot2);
    a[2][3] = cplx_div(a[2][3], pivot2);
    b[2] = cplx_div(b[2], pivot2);
    let factor2_0 = a[0][2];
    if (cplx_norm_sqr(factor2_0) != 0.0) {
        a[0][2] = cplx_sub(a[0][2], cplx_mul(factor2_0, a[2][2]));
        a[0][3] = cplx_sub(a[0][3], cplx_mul(factor2_0, a[2][3]));
        b[0] = cplx_sub(b[0], cplx_mul(factor2_0, b[2]));
    }
    let factor2_1 = a[1][2];
    if (cplx_norm_sqr(factor2_1) != 0.0) {
        a[1][2] = cplx_sub(a[1][2], cplx_mul(factor2_1, a[2][2]));
        a[1][3] = cplx_sub(a[1][3], cplx_mul(factor2_1, a[2][3]));
        b[1] = cplx_sub(b[1], cplx_mul(factor2_1, b[2]));
    }
    let factor2_3 = a[3][2];
    if (cplx_norm_sqr(factor2_3) != 0.0) {
        a[3][2] = cplx_sub(a[3][2], cplx_mul(factor2_3, a[2][2]));
        a[3][3] = cplx_sub(a[3][3], cplx_mul(factor2_3, a[2][3]));
        b[3] = cplx_sub(b[3], cplx_mul(factor2_3, b[2]));
    }
    // column 3: pivot search
    var piv3: u32 = 3u;
    var piv_mag3: f32 = cplx_norm_sqr(a[3][3]);
    let pivot3 = a[3][3];
    a[3][3] = cplx_div(a[3][3], pivot3);
    b[3] = cplx_div(b[3], pivot3);
    let factor3_0 = a[0][3];
    if (cplx_norm_sqr(factor3_0) != 0.0) {
        a[0][3] = cplx_sub(a[0][3], cplx_mul(factor3_0, a[3][3]));
        b[0] = cplx_sub(b[0], cplx_mul(factor3_0, b[3]));
    }
    let factor3_1 = a[1][3];
    if (cplx_norm_sqr(factor3_1) != 0.0) {
        a[1][3] = cplx_sub(a[1][3], cplx_mul(factor3_1, a[3][3]));
        b[1] = cplx_sub(b[1], cplx_mul(factor3_1, b[3]));
    }
    let factor3_2 = a[2][3];
    if (cplx_norm_sqr(factor3_2) != 0.0) {
        a[2][3] = cplx_sub(a[2][3], cplx_mul(factor3_2, a[3][3]));
        b[2] = cplx_sub(b[2], cplx_mul(factor3_2, b[3]));
    }
    return b;
}

// optics::raytracer::uniaxial_fresnel::solve4_two_rhs
struct Solve4TwoRhsResult {
    b1: array<Cplx, 4>,
    b2: array<Cplx, 4>,
}

fn solve4_two_rhs(a_in: array<array<Cplx, 4>, 4>, b1_in: array<Cplx, 4>, b2_in: array<Cplx, 4>) -> Solve4TwoRhsResult {
    var a = a_in;
    var b1 = b1_in;
    var b2 = b2_in;
    // column 0: pivot search
    var piv0: u32 = 0u;
    var piv_mag0: f32 = cplx_norm_sqr(a[0][0]);
    let mag0_1 = cplx_norm_sqr(a[1][0]);
    if (mag0_1 > piv_mag0) {
        piv0 = 1u;
        piv_mag0 = mag0_1;
    }
    let mag0_2 = cplx_norm_sqr(a[2][0]);
    if (mag0_2 > piv_mag0) {
        piv0 = 2u;
        piv_mag0 = mag0_2;
    }
    let mag0_3 = cplx_norm_sqr(a[3][0]);
    if (mag0_3 > piv_mag0) {
        piv0 = 3u;
        piv_mag0 = mag0_3;
    }
    if (piv0 == 1u) {
        let t0_1_0 = a[0][0];
        a[0][0] = a[1][0];
        a[1][0] = t0_1_0;
        let t0_1_1 = a[0][1];
        a[0][1] = a[1][1];
        a[1][1] = t0_1_1;
        let t0_1_2 = a[0][2];
        a[0][2] = a[1][2];
        a[1][2] = t0_1_2;
        let t0_1_3 = a[0][3];
        a[0][3] = a[1][3];
        a[1][3] = t0_1_3;
        let tb0_1_b1 = b1[0];
        b1[0] = b1[1];
        b1[1] = tb0_1_b1;
        let tb0_1_b2 = b2[0];
        b2[0] = b2[1];
        b2[1] = tb0_1_b2;
    }
    if (piv0 == 2u) {
        let t0_2_0 = a[0][0];
        a[0][0] = a[2][0];
        a[2][0] = t0_2_0;
        let t0_2_1 = a[0][1];
        a[0][1] = a[2][1];
        a[2][1] = t0_2_1;
        let t0_2_2 = a[0][2];
        a[0][2] = a[2][2];
        a[2][2] = t0_2_2;
        let t0_2_3 = a[0][3];
        a[0][3] = a[2][3];
        a[2][3] = t0_2_3;
        let tb0_2_b1 = b1[0];
        b1[0] = b1[2];
        b1[2] = tb0_2_b1;
        let tb0_2_b2 = b2[0];
        b2[0] = b2[2];
        b2[2] = tb0_2_b2;
    }
    if (piv0 == 3u) {
        let t0_3_0 = a[0][0];
        a[0][0] = a[3][0];
        a[3][0] = t0_3_0;
        let t0_3_1 = a[0][1];
        a[0][1] = a[3][1];
        a[3][1] = t0_3_1;
        let t0_3_2 = a[0][2];
        a[0][2] = a[3][2];
        a[3][2] = t0_3_2;
        let t0_3_3 = a[0][3];
        a[0][3] = a[3][3];
        a[3][3] = t0_3_3;
        let tb0_3_b1 = b1[0];
        b1[0] = b1[3];
        b1[3] = tb0_3_b1;
        let tb0_3_b2 = b2[0];
        b2[0] = b2[3];
        b2[3] = tb0_3_b2;
    }
    let pivot0 = a[0][0];
    a[0][0] = cplx_div(a[0][0], pivot0);
    a[0][1] = cplx_div(a[0][1], pivot0);
    a[0][2] = cplx_div(a[0][2], pivot0);
    a[0][3] = cplx_div(a[0][3], pivot0);
    b1[0] = cplx_div(b1[0], pivot0);
    b2[0] = cplx_div(b2[0], pivot0);
    let factor0_1 = a[1][0];
    if (cplx_norm_sqr(factor0_1) != 0.0) {
        a[1][0] = cplx_sub(a[1][0], cplx_mul(factor0_1, a[0][0]));
        a[1][1] = cplx_sub(a[1][1], cplx_mul(factor0_1, a[0][1]));
        a[1][2] = cplx_sub(a[1][2], cplx_mul(factor0_1, a[0][2]));
        a[1][3] = cplx_sub(a[1][3], cplx_mul(factor0_1, a[0][3]));
        b1[1] = cplx_sub(b1[1], cplx_mul(factor0_1, b1[0]));
        b2[1] = cplx_sub(b2[1], cplx_mul(factor0_1, b2[0]));
    }
    let factor0_2 = a[2][0];
    if (cplx_norm_sqr(factor0_2) != 0.0) {
        a[2][0] = cplx_sub(a[2][0], cplx_mul(factor0_2, a[0][0]));
        a[2][1] = cplx_sub(a[2][1], cplx_mul(factor0_2, a[0][1]));
        a[2][2] = cplx_sub(a[2][2], cplx_mul(factor0_2, a[0][2]));
        a[2][3] = cplx_sub(a[2][3], cplx_mul(factor0_2, a[0][3]));
        b1[2] = cplx_sub(b1[2], cplx_mul(factor0_2, b1[0]));
        b2[2] = cplx_sub(b2[2], cplx_mul(factor0_2, b2[0]));
    }
    let factor0_3 = a[3][0];
    if (cplx_norm_sqr(factor0_3) != 0.0) {
        a[3][0] = cplx_sub(a[3][0], cplx_mul(factor0_3, a[0][0]));
        a[3][1] = cplx_sub(a[3][1], cplx_mul(factor0_3, a[0][1]));
        a[3][2] = cplx_sub(a[3][2], cplx_mul(factor0_3, a[0][2]));
        a[3][3] = cplx_sub(a[3][3], cplx_mul(factor0_3, a[0][3]));
        b1[3] = cplx_sub(b1[3], cplx_mul(factor0_3, b1[0]));
        b2[3] = cplx_sub(b2[3], cplx_mul(factor0_3, b2[0]));
    }
    // column 1: pivot search
    var piv1: u32 = 1u;
    var piv_mag1: f32 = cplx_norm_sqr(a[1][1]);
    let mag1_2 = cplx_norm_sqr(a[2][1]);
    if (mag1_2 > piv_mag1) {
        piv1 = 2u;
        piv_mag1 = mag1_2;
    }
    let mag1_3 = cplx_norm_sqr(a[3][1]);
    if (mag1_3 > piv_mag1) {
        piv1 = 3u;
        piv_mag1 = mag1_3;
    }
    if (piv1 == 2u) {
        let t1_2_0 = a[1][0];
        a[1][0] = a[2][0];
        a[2][0] = t1_2_0;
        let t1_2_1 = a[1][1];
        a[1][1] = a[2][1];
        a[2][1] = t1_2_1;
        let t1_2_2 = a[1][2];
        a[1][2] = a[2][2];
        a[2][2] = t1_2_2;
        let t1_2_3 = a[1][3];
        a[1][3] = a[2][3];
        a[2][3] = t1_2_3;
        let tb1_2_b1 = b1[1];
        b1[1] = b1[2];
        b1[2] = tb1_2_b1;
        let tb1_2_b2 = b2[1];
        b2[1] = b2[2];
        b2[2] = tb1_2_b2;
    }
    if (piv1 == 3u) {
        let t1_3_0 = a[1][0];
        a[1][0] = a[3][0];
        a[3][0] = t1_3_0;
        let t1_3_1 = a[1][1];
        a[1][1] = a[3][1];
        a[3][1] = t1_3_1;
        let t1_3_2 = a[1][2];
        a[1][2] = a[3][2];
        a[3][2] = t1_3_2;
        let t1_3_3 = a[1][3];
        a[1][3] = a[3][3];
        a[3][3] = t1_3_3;
        let tb1_3_b1 = b1[1];
        b1[1] = b1[3];
        b1[3] = tb1_3_b1;
        let tb1_3_b2 = b2[1];
        b2[1] = b2[3];
        b2[3] = tb1_3_b2;
    }
    let pivot1 = a[1][1];
    a[1][1] = cplx_div(a[1][1], pivot1);
    a[1][2] = cplx_div(a[1][2], pivot1);
    a[1][3] = cplx_div(a[1][3], pivot1);
    b1[1] = cplx_div(b1[1], pivot1);
    b2[1] = cplx_div(b2[1], pivot1);
    let factor1_0 = a[0][1];
    if (cplx_norm_sqr(factor1_0) != 0.0) {
        a[0][1] = cplx_sub(a[0][1], cplx_mul(factor1_0, a[1][1]));
        a[0][2] = cplx_sub(a[0][2], cplx_mul(factor1_0, a[1][2]));
        a[0][3] = cplx_sub(a[0][3], cplx_mul(factor1_0, a[1][3]));
        b1[0] = cplx_sub(b1[0], cplx_mul(factor1_0, b1[1]));
        b2[0] = cplx_sub(b2[0], cplx_mul(factor1_0, b2[1]));
    }
    let factor1_2 = a[2][1];
    if (cplx_norm_sqr(factor1_2) != 0.0) {
        a[2][1] = cplx_sub(a[2][1], cplx_mul(factor1_2, a[1][1]));
        a[2][2] = cplx_sub(a[2][2], cplx_mul(factor1_2, a[1][2]));
        a[2][3] = cplx_sub(a[2][3], cplx_mul(factor1_2, a[1][3]));
        b1[2] = cplx_sub(b1[2], cplx_mul(factor1_2, b1[1]));
        b2[2] = cplx_sub(b2[2], cplx_mul(factor1_2, b2[1]));
    }
    let factor1_3 = a[3][1];
    if (cplx_norm_sqr(factor1_3) != 0.0) {
        a[3][1] = cplx_sub(a[3][1], cplx_mul(factor1_3, a[1][1]));
        a[3][2] = cplx_sub(a[3][2], cplx_mul(factor1_3, a[1][2]));
        a[3][3] = cplx_sub(a[3][3], cplx_mul(factor1_3, a[1][3]));
        b1[3] = cplx_sub(b1[3], cplx_mul(factor1_3, b1[1]));
        b2[3] = cplx_sub(b2[3], cplx_mul(factor1_3, b2[1]));
    }
    // column 2: pivot search
    var piv2: u32 = 2u;
    var piv_mag2: f32 = cplx_norm_sqr(a[2][2]);
    let mag2_3 = cplx_norm_sqr(a[3][2]);
    if (mag2_3 > piv_mag2) {
        piv2 = 3u;
        piv_mag2 = mag2_3;
    }
    if (piv2 == 3u) {
        let t2_3_0 = a[2][0];
        a[2][0] = a[3][0];
        a[3][0] = t2_3_0;
        let t2_3_1 = a[2][1];
        a[2][1] = a[3][1];
        a[3][1] = t2_3_1;
        let t2_3_2 = a[2][2];
        a[2][2] = a[3][2];
        a[3][2] = t2_3_2;
        let t2_3_3 = a[2][3];
        a[2][3] = a[3][3];
        a[3][3] = t2_3_3;
        let tb2_3_b1 = b1[2];
        b1[2] = b1[3];
        b1[3] = tb2_3_b1;
        let tb2_3_b2 = b2[2];
        b2[2] = b2[3];
        b2[3] = tb2_3_b2;
    }
    let pivot2 = a[2][2];
    a[2][2] = cplx_div(a[2][2], pivot2);
    a[2][3] = cplx_div(a[2][3], pivot2);
    b1[2] = cplx_div(b1[2], pivot2);
    b2[2] = cplx_div(b2[2], pivot2);
    let factor2_0 = a[0][2];
    if (cplx_norm_sqr(factor2_0) != 0.0) {
        a[0][2] = cplx_sub(a[0][2], cplx_mul(factor2_0, a[2][2]));
        a[0][3] = cplx_sub(a[0][3], cplx_mul(factor2_0, a[2][3]));
        b1[0] = cplx_sub(b1[0], cplx_mul(factor2_0, b1[2]));
        b2[0] = cplx_sub(b2[0], cplx_mul(factor2_0, b2[2]));
    }
    let factor2_1 = a[1][2];
    if (cplx_norm_sqr(factor2_1) != 0.0) {
        a[1][2] = cplx_sub(a[1][2], cplx_mul(factor2_1, a[2][2]));
        a[1][3] = cplx_sub(a[1][3], cplx_mul(factor2_1, a[2][3]));
        b1[1] = cplx_sub(b1[1], cplx_mul(factor2_1, b1[2]));
        b2[1] = cplx_sub(b2[1], cplx_mul(factor2_1, b2[2]));
    }
    let factor2_3 = a[3][2];
    if (cplx_norm_sqr(factor2_3) != 0.0) {
        a[3][2] = cplx_sub(a[3][2], cplx_mul(factor2_3, a[2][2]));
        a[3][3] = cplx_sub(a[3][3], cplx_mul(factor2_3, a[2][3]));
        b1[3] = cplx_sub(b1[3], cplx_mul(factor2_3, b1[2]));
        b2[3] = cplx_sub(b2[3], cplx_mul(factor2_3, b2[2]));
    }
    // column 3: pivot search
    var piv3: u32 = 3u;
    var piv_mag3: f32 = cplx_norm_sqr(a[3][3]);
    let pivot3 = a[3][3];
    a[3][3] = cplx_div(a[3][3], pivot3);
    b1[3] = cplx_div(b1[3], pivot3);
    b2[3] = cplx_div(b2[3], pivot3);
    let factor3_0 = a[0][3];
    if (cplx_norm_sqr(factor3_0) != 0.0) {
        a[0][3] = cplx_sub(a[0][3], cplx_mul(factor3_0, a[3][3]));
        b1[0] = cplx_sub(b1[0], cplx_mul(factor3_0, b1[3]));
        b2[0] = cplx_sub(b2[0], cplx_mul(factor3_0, b2[3]));
    }
    let factor3_1 = a[1][3];
    if (cplx_norm_sqr(factor3_1) != 0.0) {
        a[1][3] = cplx_sub(a[1][3], cplx_mul(factor3_1, a[3][3]));
        b1[1] = cplx_sub(b1[1], cplx_mul(factor3_1, b1[3]));
        b2[1] = cplx_sub(b2[1], cplx_mul(factor3_1, b2[3]));
    }
    let factor3_2 = a[2][3];
    if (cplx_norm_sqr(factor3_2) != 0.0) {
        a[2][3] = cplx_sub(a[2][3], cplx_mul(factor3_2, a[3][3]));
        b1[2] = cplx_sub(b1[2], cplx_mul(factor3_2, b1[3]));
        b2[2] = cplx_sub(b2[2], cplx_mul(factor3_2, b2[3]));
    }
    var result: Solve4TwoRhsResult;
    result.b1 = b1;
    result.b2 = b2;
    return result;
}
// END GENERATED solve4