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
use std::ops::{Add, AddAssign, Div, Mul};
use crate::core::geometry::{Point2f, Point2i, Vector2f};
use crate::core::memory::BlockedArray;
use crate::core::pbrt::{clamp_t, is_power_of_2, lerp, mod_t, round_up_pow2_32};
use crate::core::pbrt::{Float, Spectrum};
use crate::core::texture::lanczos;
const WEIGHT_LUT_SIZE: usize = 128;
#[derive(Debug, Clone)]
pub enum ImageWrap {
Repeat,
Black,
Clamp,
}
#[derive(Debug, Default, Copy, Clone)]
pub struct ResampleWeight {
pub first_texel: i32,
pub weight: [Float; 4],
}
pub struct MipMap<T> {
pub do_trilinear: bool,
pub max_anisotropy: Float,
pub wrap_mode: ImageWrap,
pub resolution: Point2i,
pub pyramid: Vec<BlockedArray<T>>,
pub weight_lut: [Float; WEIGHT_LUT_SIZE],
}
impl<T> MipMap<T>
where
T: std::default::Default
+ num::Zero
+ std::clone::Clone
+ Add<T, Output = T>
+ AddAssign
+ Clampable
+ Copy
+ Div<Float, Output = T>
+ Mul<T, Output = T>
+ Mul<Float, Output = T>,
{
pub fn new(
res: Point2i,
img: &[T],
do_trilinear: bool,
max_anisotropy: Float,
wrap_mode: ImageWrap,
) -> Self {
let mut resolution = res;
let mut resampled_image: Vec<T> = Vec::new();
if !is_power_of_2(resolution.x) || !is_power_of_2(resolution.y) {
let res_pow_2: Point2i = Point2i {
x: round_up_pow2_32(resolution.x),
y: round_up_pow2_32(resolution.y),
};
let s_weights: Vec<ResampleWeight> =
MipMap::<T>::resample_weights(resolution.x, res_pow_2.x);
resampled_image = vec![T::default(); (res_pow_2.x * res_pow_2.y) as usize];
for t in 0..resolution.y {
for s in 0..res_pow_2.x {
resampled_image[(t * res_pow_2.x + s) as usize] = T::default();
for j in 0..4 {
let mut orig_s: i32 = s_weights[s as usize].first_texel + j as i32;
orig_s = match wrap_mode {
ImageWrap::Repeat => mod_t(orig_s, resolution.x),
ImageWrap::Clamp => clamp_t(orig_s, 0_i32, resolution.x - 1_i32),
_ => orig_s,
};
if orig_s >= 0_i32 && orig_s < resolution.x {
resampled_image[(t * res_pow_2.x + s) as usize] += img
[(t * resolution.x + orig_s) as usize]
* s_weights[s as usize].weight[j];
}
}
}
}
let t_weights: Vec<ResampleWeight> =
MipMap::<T>::resample_weights(resolution.y, res_pow_2.y);
let mut work_data: Vec<T> = vec![T::default(); res_pow_2.y as usize];
for s in 0..res_pow_2.x {
for t in 0..res_pow_2.y {
work_data[t as usize] = T::default();
for j in 0..4 {
let mut offset: i32 = t_weights[t as usize].first_texel + j as i32;
offset = match wrap_mode {
ImageWrap::Repeat => mod_t(offset, resolution.y),
ImageWrap::Clamp => clamp_t(offset, 0_i32, resolution.y - 1_i32),
_ => offset,
};
if offset >= 0_i32 && offset < resolution.y {
work_data[t as usize] += resampled_image
[(offset * res_pow_2.x + s) as usize]
* t_weights[t as usize].weight[j];
}
}
}
for t in 0..res_pow_2.y {
resampled_image[(t * res_pow_2.x + s) as usize] = Clampable::clamp(
work_data[t as usize],
0.0 as Float,
std::f32::INFINITY as Float,
);
}
}
resolution = res_pow_2;
}
let mut mipmap = MipMap::<T> {
do_trilinear,
max_anisotropy,
wrap_mode,
resolution,
pyramid: Vec::new(),
weight_lut: [0.0 as Float; WEIGHT_LUT_SIZE],
};
let n_levels = 1 + (std::cmp::max(resolution.x, resolution.y) as Float).log2() as usize;
let img_data: &[T] = if resampled_image.is_empty() {
img
} else {
&resampled_image[..]
};
mipmap.pyramid.push(BlockedArray::new_from(
resolution.x as usize,
resolution.y as usize,
img_data,
));
for i in 1..n_levels {
let s_res = std::cmp::max(1, mipmap.pyramid[i - 1].u_size() / 2);
let t_res = std::cmp::max(1, mipmap.pyramid[i - 1].v_size() / 2);
let mut ba = BlockedArray::<T>::new(s_res, t_res);
for t in 0..t_res {
for s in 0..s_res {
let (si, ti) = (s as isize, t as isize);
ba[(s, t)] = (*mipmap.texel(i - 1, 2 * si, 2 * ti)
+ *mipmap.texel(i - 1, 2 * si + 1, 2 * ti)
+ *mipmap.texel(i - 1, 2 * si, 2 * ti + 1)
+ *mipmap.texel(i - 1, 2 * si + 1, 2 * ti + 1))
as T
* 0.25 as Float;
}
}
mipmap.pyramid.push(ba);
}
if mipmap.weight_lut[0] == 0.0 as Float {
for i in 0..WEIGHT_LUT_SIZE {
let alpha: Float = 2.0 as Float;
let r2: Float = i as Float / (WEIGHT_LUT_SIZE - 1) as Float;
mipmap.weight_lut[i] = (-alpha * r2).exp() - (-alpha).exp();
}
}
mipmap
}
pub fn width(&self) -> i32 {
self.resolution.x
}
pub fn height(&self) -> i32 {
self.resolution.y
}
pub fn levels(&self) -> usize {
self.pyramid.len()
}
pub fn texel(&self, level: usize, s: isize, t: isize) -> &T {
let l = &self.pyramid[level];
let (u_size, v_size) = (l.u_size() as isize, l.v_size() as isize);
let (ss, tt): (usize, usize) = match self.wrap_mode {
ImageWrap::Repeat => (
mod_t(s as usize, u_size as usize),
mod_t(t as usize, v_size as usize),
),
ImageWrap::Clamp => (
clamp_t(s, 0, u_size - 1) as usize,
clamp_t(t, 0, v_size - 1) as usize,
),
ImageWrap::Black => {
if s < 0 || s >= u_size || t < 0 || t >= v_size {
(
clamp_t(s, 0, u_size - 1) as usize,
clamp_t(t, 0, v_size - 1) as usize,
)
} else {
(s as usize, t as usize)
}
}
};
&l[(ss, tt)]
}
pub fn lookup_pnt_flt(&self, st: Point2f, width: Float) -> T {
let level: Float = self.levels() as Float - 1.0 as Float + width.max(1e-8 as Float).log2();
if level < 0.0 as Float {
self.triangle(0_usize, st)
} else if level >= self.levels() as Float - 1.0 as Float {
*self.texel(self.levels() - 1, 0_isize, 0_isize)
} else {
let i_level: usize = level.floor() as usize;
let delta: Float = level - i_level as Float;
lerp(
delta,
self.triangle(i_level, st),
self.triangle(i_level + 1_usize, st),
)
}
}
pub fn lookup_pnt_vec_vec(&self, st: Point2f, dst0: &mut Vector2f, dst1: &mut Vector2f) -> T {
if self.do_trilinear {
let width: Float = dst0
.x
.abs()
.max(dst0.y.abs())
.max(dst1.x.abs().max(dst1.y.abs()));
return self.lookup_pnt_flt(st, width);
}
if dst0.length_squared() < dst1.length_squared() {
let swap: Vector2f = Vector2f {
x: dst0.x,
y: dst0.y,
};
dst0.x = dst1.x;
dst0.y = dst1.y;
dst1.x = swap.x;
dst1.y = swap.y;
}
let major_length: Float = dst0.length();
let mut minor_length: Float = dst1.length();
if minor_length * self.max_anisotropy < major_length && minor_length > 0.0 as Float {
let scale: Float = major_length / (minor_length * self.max_anisotropy);
*dst1 *= scale;
minor_length *= scale;
}
if minor_length == 0.0 as Float {
return self.triangle(0, st);
}
let lod: Float = (0.0 as Float)
.max(self.levels() as Float - 1.0 as Float + minor_length.log2() as Float);
let ilod: usize = lod.floor() as usize;
let col2: T = self.ewa(ilod + 1, st, *dst0, *dst1);
let col1: T = self.ewa(ilod, st, *dst0, *dst1);
let ret: T = lerp(lod - ilod as Float, col1, col2);
ret
}
fn resample_weights(old_res: i32, new_res: i32) -> Vec<ResampleWeight> {
assert!(new_res >= old_res);
let mut wt: Vec<ResampleWeight> = Vec::with_capacity(new_res as usize);
let filterwidth: Float = 2.0 as Float;
for i in 0..new_res {
let center: Float = (i as Float + 0.5 as Float) * old_res as Float / new_res as Float;
let mut rw: ResampleWeight = ResampleWeight::default();
rw.first_texel = ((center - filterwidth) + 0.5 as Float).floor() as i32;
for j in 0..4 {
let pos: Float = rw.first_texel as Float + j as Float + 0.5 as Float;
rw.weight[j] = lanczos((pos - center) / filterwidth, 2.0 as Float);
}
let inv_sum_wts: Float =
1.0 as Float / (rw.weight[0] + rw.weight[1] + rw.weight[2] + rw.weight[3]);
for j in 0..4 {
rw.weight[j] *= inv_sum_wts;
}
wt.push(rw);
}
wt
}
fn triangle(&self, level: usize, st: Point2f) -> T {
let level: usize = clamp_t(level, 0_usize, self.levels() - 1_usize);
let s: Float = st.x * self.pyramid[level].u_size() as Float - 0.5;
let t: Float = st.y * self.pyramid[level].v_size() as Float - 0.5;
let s0: isize = s.floor() as isize;
let t0: isize = t.floor() as isize;
let ds: Float = s - s0 as Float;
let dt: Float = t - t0 as Float;
let tmp1: T = *self.texel(level, s0 + 1, t0 + 1) * (ds * dt);
let tmp2: T = *self.texel(level, s0 + 1, t0) * (ds * (1.0 - dt));
let tmp3: T = *self.texel(level, s0, t0 + 1) * ((1.0 - ds) * dt);
let tmp4: T = *self.texel(level, s0, t0) * ((1.0 - ds) * (1.0 - dt));
tmp4 + tmp3 + tmp2 + tmp1
}
fn ewa(&self, level: usize, st: Point2f, dst0: Vector2f, dst1: Vector2f) -> T {
if level >= self.levels() {
return *self.texel(self.levels() - 1, 0, 0);
}
let mut new_st: Vector2f = Vector2f { x: st.x, y: st.y };
new_st.x = new_st.x * self.pyramid[level].u_size() as Float - 0.5 as Float;
new_st.y = new_st.y * self.pyramid[level].v_size() as Float - 0.5 as Float;
let mut new_dst0: Vector2f = Vector2f {
x: dst0.x,
y: dst0.y,
};
let mut new_dst1: Vector2f = Vector2f {
x: dst1.x,
y: dst1.y,
};
new_dst0.x *= self.pyramid[level].u_size() as Float;
new_dst0.y *= self.pyramid[level].v_size() as Float;
new_dst1.x *= self.pyramid[level].u_size() as Float;
new_dst1.y *= self.pyramid[level].v_size() as Float;
let mut a: Float = new_dst0.y * new_dst0.y + new_dst1.y * new_dst1.y + 1.0 as Float;
let mut b: Float = -2.0 as Float * (new_dst0.x * new_dst0.y + new_dst1.x * new_dst1.y);
let mut c: Float = new_dst0.x * new_dst0.x + new_dst1.x * new_dst1.x + 1.0 as Float;
let inv_f: Float = 1.0 as Float / (a * c - b * b * 0.25 as Float);
a *= inv_f;
b *= inv_f;
c *= inv_f;
let det: Float = -b * b + 4.0 as Float * a * c;
let inv_det: Float = 1.0 as Float / det;
let u_sqrt: Float = (det * c).sqrt();
let v_sqrt: Float = (a * det).sqrt();
let s0: isize = (new_st.x - 2.0 as Float * inv_det * u_sqrt).ceil() as isize;
let s1: isize = (new_st.x + 2.0 as Float * inv_det * u_sqrt).floor() as isize;
let t0: isize = (new_st.y - 2.0 as Float * inv_det * v_sqrt).ceil() as isize;
let t1: isize = (new_st.y + 2.0 as Float * inv_det * v_sqrt).floor() as isize;
let mut sum: T = T::default();
let mut sum_wts: Float = 0.0;
for it in t0..=t1 {
let tt: Float = it as Float - new_st.y;
for is in s0..=s1 {
let ss: Float = is as Float - new_st.x;
let r2: Float = a * ss * ss + b * ss * tt + c * tt * tt;
if r2 < 1.0 as Float {
let index: usize = std::cmp::min(
(r2 * WEIGHT_LUT_SIZE as Float) as usize,
WEIGHT_LUT_SIZE - 1,
);
let weight: Float = self.weight_lut[index];
sum += *self.texel(level, is as isize, it as isize) * weight;
sum_wts += weight;
}
}
}
sum / sum_wts
}
}
pub trait Clampable {
fn clamp(self, min: Float, max: Float) -> Self;
}
impl Clampable for Float {
fn clamp(self, min: Float, max: Float) -> Float {
clamp_t(self, min, max)
}
}
impl Clampable for Spectrum {
fn clamp(self, min: Float, max: Float) -> Spectrum {
Spectrum::rgb(
clamp_t(self.c[0], min, max),
clamp_t(self.c[1], min, max),
clamp_t(self.c[2], min, max),
)
}
}