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
// std
use std::f32::consts::PI;
use std::sync::Arc;
// pbrt
use crate::core::efloat::quadratic_efloat;
use crate::core::efloat::EFloat;
use crate::core::geometry::{
    nrm_abs_dot_vec3f, pnt3_distance_squaredf, vec3_cross_vec3, vec3_dot_vec3f,
};
use crate::core::geometry::{Bounds3f, Normal3f, Point2f, Point3f, Ray, Vector3f, XYEnum};
use crate::core::interaction::{Interaction, InteractionCommon, SurfaceInteraction};
use crate::core::material::Material;
use crate::core::pbrt::Float;
use crate::core::pbrt::{clamp_t, gamma, lerp, radians};
use crate::core::transform::Transform;

// see cylinder.h

#[derive(Clone)]
pub struct Cylinder {
    pub radius: Float,
    pub z_min: Float,
    pub z_max: Float,
    pub phi_max: Float,
    // inherited from class Shape (see shape.h)
    pub object_to_world: Transform,
    pub world_to_object: Transform,
    pub reverse_orientation: bool,
    pub transform_swaps_handedness: bool,
    pub material: Option<Arc<Material>>,
}

impl Default for Cylinder {
    fn default() -> Self {
        let object_to_world: Transform = Transform::default();
        Cylinder {
            // Shape
            object_to_world,
            world_to_object: Transform::default(),
            reverse_orientation: false,
            transform_swaps_handedness: object_to_world.swaps_handedness(),
            // Cylinder
            radius: 1.0,
            z_min: -1.0,
            z_max: 1.0,
            phi_max: radians(360.0),
            material: None,
        }
    }
}

impl Cylinder {
    pub fn new(
        object_to_world: Transform,
        world_to_object: Transform,
        reverse_orientation: bool,
        radius: Float,
        z_min: Float,
        z_max: Float,
        phi_max: Float,
    ) -> Self {
        Cylinder {
            // Shape
            object_to_world,
            world_to_object,
            reverse_orientation,
            transform_swaps_handedness: object_to_world.swaps_handedness(),
            // Cylinder
            radius,
            z_min: z_min.min(z_max),
            z_max: z_min.max(z_max),
            phi_max: radians(clamp_t(phi_max, 0.0, 360.0)),
            material: None,
        }
    }
    // Shape
    pub fn object_bound(&self) -> Bounds3f {
        Bounds3f {
            p_min: Point3f {
                x: -self.radius,
                y: -self.radius,
                z: self.z_min,
            },
            p_max: Point3f {
                x: self.radius,
                y: self.radius,
                z: self.z_max,
            },
        }
    }
    pub fn world_bound(&self) -> Bounds3f {
        // in C++: Bounds3f Shape::WorldBound() const { return (*ObjectToWorld)(ObjectBound()); }
        self.object_to_world.transform_bounds(&self.object_bound())
    }
    pub fn intersect(&self, r: &Ray, t_hit: &mut Float, isect: &mut SurfaceInteraction) -> bool {
        // TODO: ProfilePhase p(Prof::ShapeIntersect);
        // transform _Ray_ to object space
        let mut o_err: Vector3f = Vector3f::default();
        let mut d_err: Vector3f = Vector3f::default();
        let ray: Ray = self
            .world_to_object
            .transform_ray_with_error(r, &mut o_err, &mut d_err);

        // compute quadratic cylinder coefficients

        // initialize _EFloat_ ray coordinate values
        let ox = EFloat::new(ray.o.x, o_err.x);
        let oy = EFloat::new(ray.o.y, o_err.y);
        // let oz = EFloat::new(ray.o.z, o_err.z);
        let dx = EFloat::new(ray.d.x, d_err.x);
        let dy = EFloat::new(ray.d.y, d_err.y);
        // let dz = EFloat::new(ray.d.z, d_err.z);
        let a: EFloat = dx * dx + dy * dy;
        let b: EFloat = (dx * ox + dy * oy) * 2.0f32;
        let c: EFloat =
            ox * ox + oy * oy - EFloat::new(self.radius, 0.0) * EFloat::new(self.radius, 0.0);

        // Solve quadratic equation for _t_ values
        let mut t0: EFloat = EFloat::default();
        let mut t1: EFloat = EFloat::default();
        if !quadratic_efloat(a, b, c, &mut t0, &mut t1) {
            return false;
        }
        // check quadric shape _t0_ and _t1_ for nearest intersection
        if t0.upper_bound() > ray.t_max.get() || t1.lower_bound() <= 0.0f32 {
            return false;
        }
        let mut t_shape_hit: EFloat = t0;
        if t_shape_hit.lower_bound() <= 0.0f32 {
            t_shape_hit = t1;
            if t_shape_hit.upper_bound() > ray.t_max.get() {
                return false;
            }
        }
        // compute cylinder hit point and $\phi$
        let mut p_hit: Point3f = ray.position(t_shape_hit.v);
        // refine cylinder intersection point
        let hit_rad: Float = (p_hit.x * p_hit.x + p_hit.y * p_hit.y).sqrt();
        p_hit.x *= self.radius / hit_rad;
        p_hit.y *= self.radius / hit_rad;
        let mut phi: Float = p_hit.y.atan2(p_hit.x);
        if phi < 0.0 as Float {
            phi += 2.0 as Float * PI;
        }
        // test cylinder intersection against clipping parameters
        if p_hit.z < self.z_min || p_hit.z > self.z_max || phi > self.phi_max {
            if t_shape_hit == t1 {
                return false;
            }
            t_shape_hit = t1;
            if t1.upper_bound() > ray.t_max.get() {
                return false;
            }
            // compute cylinder hit point and $\phi$
            p_hit = ray.position(t_shape_hit.v);

            // refine cylinder intersection point
            let hit_rad: Float = (p_hit.x * p_hit.x + p_hit.y * p_hit.y).sqrt();
            p_hit.x *= self.radius / hit_rad;
            p_hit.y *= self.radius / hit_rad;
            phi = p_hit.y.atan2(p_hit.x);
            if phi < 0.0 as Float {
                phi += 2.0 as Float * PI;
            }
            if p_hit.z < self.z_min || p_hit.z > self.z_max || phi > self.phi_max {
                return false;
            }
        }
        // find parametric representation of cylinder hit
        let u: Float = phi / self.phi_max;
        let v: Float = (p_hit.z - self.z_min) / (self.z_max - self.z_min);
        // Compute cylinder $\dpdu$ and $\dpdv$
        let dpdu: Vector3f = Vector3f {
            x: -self.phi_max * p_hit.y,
            y: self.phi_max * p_hit.x,
            z: 0.0,
        };
        let dpdv: Vector3f = Vector3f {
            x: 0.0,
            y: 0.0,
            z: self.z_max - self.z_min,
        };
        // compute cylinder $\dndu$ and $\dndv$
        let d2_p_duu: Vector3f = Vector3f {
            x: p_hit.x,
            y: p_hit.y,
            z: 0.0,
        } * -self.phi_max
            * self.phi_max;
        let d2_p_duv: Vector3f = Vector3f {
            x: 0.0,
            y: 0.0,
            z: 0.0,
        };
        let d2_p_dvv: Vector3f = Vector3f {
            x: 0.0,
            y: 0.0,
            z: 0.0,
        };
        // compute coefficients for fundamental forms
        let ec: Float = vec3_dot_vec3f(&dpdu, &dpdu);
        let fc: Float = vec3_dot_vec3f(&dpdu, &dpdv);
        let gc: Float = vec3_dot_vec3f(&dpdv, &dpdv);
        let nc: Vector3f = vec3_cross_vec3(&dpdu, &dpdv).normalize();
        let el: Float = vec3_dot_vec3f(&nc, &d2_p_duu);
        let fl: Float = vec3_dot_vec3f(&nc, &d2_p_duv);
        let gl: Float = vec3_dot_vec3f(&nc, &d2_p_dvv);
        // compute $\dndu$ and $\dndv$ from fundamental form coefficients
        let inv_egf2: Float = 1.0 / (ec * gc - fc * fc);
        let dndu = dpdu * (fl * fc - el * gc) * inv_egf2 + dpdv * (el * fc - fl * ec) * inv_egf2;
        let dndu = Normal3f {
            x: dndu.x,
            y: dndu.y,
            z: dndu.z,
        };
        let dndv = dpdu * (gl * fc - fl * gc) * inv_egf2 + dpdv * (fl * fc - gl * ec) * inv_egf2;
        let dndv = Normal3f {
            x: dndv.x,
            y: dndv.y,
            z: dndv.z,
        };
        // compute error bounds for cylinder intersection
        let p_error: Vector3f = Vector3f {
            x: p_hit.x,
            y: p_hit.y,
            z: 0.0,
        }
        .abs()
            * gamma(3_i32);
        // initialize _SurfaceInteraction_ from parametric information
        let uv_hit: Point2f = Point2f { x: u, y: v };
        let wo: Vector3f = -ray.d;
        *isect = SurfaceInteraction::new(
            &p_hit, &p_error, uv_hit, &wo, &dpdu, &dpdv, &dndu, &dndv, ray.time, None,
        );
        self.object_to_world.transform_surface_interaction(isect);
        // if let Some(ref shape) = si.shape {
        //     isect.shape = Some(shape.clone());
        // }
        // if let Some(primitive) = si.primitive {
        //     isect.primitive = Some(primitive.clone());
        // }
        *t_hit = t_shape_hit.v as Float;
        true
    }
    pub fn intersect_p(&self, r: &Ray) -> bool {
        // TODO: ProfilePhase p(Prof::ShapeIntersect);
        // transform _Ray_ to object space
        let mut o_err: Vector3f = Vector3f::default();
        let mut d_err: Vector3f = Vector3f::default();
        let ray: Ray = self
            .world_to_object
            .transform_ray_with_error(r, &mut o_err, &mut d_err);

        // compute quadratic cylinder coefficients

        // initialize _EFloat_ ray coordinate values
        let ox = EFloat::new(ray.o.x, o_err.x);
        let oy = EFloat::new(ray.o.y, o_err.y);
        // let oz = EFloat::new(ray.o.z, o_err.z);
        let dx = EFloat::new(ray.d.x, d_err.x);
        let dy = EFloat::new(ray.d.y, d_err.y);
        // let dz = EFloat::new(ray.d.z, d_err.z);
        let a: EFloat = dx * dx + dy * dy;
        let b: EFloat = (dx * ox + dy * oy) * 2.0f32;
        let c: EFloat =
            ox * ox + oy * oy - EFloat::new(self.radius, 0.0) * EFloat::new(self.radius, 0.0);

        // Solve quadratic equation for _t_ values
        let mut t0: EFloat = EFloat::default();
        let mut t1: EFloat = EFloat::default();
        if !quadratic_efloat(a, b, c, &mut t0, &mut t1) {
            return false;
        }
        // check quadric shape _t0_ and _t1_ for nearest intersection
        if t0.upper_bound() > ray.t_max.get() || t1.lower_bound() <= 0.0f32 {
            return false;
        }
        let mut t_shape_hit: EFloat = t0;
        if t_shape_hit.lower_bound() <= 0.0f32 {
            t_shape_hit = t1;
            if t_shape_hit.upper_bound() > ray.t_max.get() {
                return false;
            }
        }
        // compute cylinder hit point and $\phi$
        let mut p_hit: Point3f = ray.position(t_shape_hit.v);
        // refine cylinder intersection point
        let hit_rad: Float = (p_hit.x * p_hit.x + p_hit.y * p_hit.y).sqrt();
        p_hit.x *= self.radius / hit_rad;
        p_hit.y *= self.radius / hit_rad;
        let mut phi: Float = p_hit.y.atan2(p_hit.x);
        if phi < 0.0 as Float {
            phi += 2.0 as Float * PI;
        }
        // test cylinder intersection against clipping parameters
        if p_hit.z < self.z_min || p_hit.z > self.z_max || phi > self.phi_max {
            if t_shape_hit == t1 {
                return false;
            }
            t_shape_hit = t1;
            if t1.upper_bound() > ray.t_max.get() {
                return false;
            }
            // compute cylinder hit point and $\phi$
            p_hit = ray.position(t_shape_hit.v);

            // refine cylinder intersection point
            let hit_rad: Float = (p_hit.x * p_hit.x + p_hit.y * p_hit.y).sqrt();
            p_hit.x *= self.radius / hit_rad;
            p_hit.y *= self.radius / hit_rad;
            phi = p_hit.y.atan2(p_hit.x);
            if phi < 0.0 as Float {
                phi += 2.0 as Float * PI;
            }
            if p_hit.z < self.z_min || p_hit.z > self.z_max || phi > self.phi_max {
                return false;
            }
        }
        true
    }
    pub fn get_reverse_orientation(&self) -> bool {
        self.reverse_orientation
    }
    pub fn get_transform_swaps_handedness(&self) -> bool {
        self.transform_swaps_handedness
    }
    pub fn get_object_to_world(&self) -> Transform {
        self.object_to_world
    }
    pub fn area(&self) -> Float {
        (self.z_max - self.z_min) * self.radius * self.phi_max
    }
    pub fn sample(&self, u: Point2f, pdf: &mut Float) -> InteractionCommon {
        let z: Float = lerp(u[XYEnum::X], self.z_min, self.z_max);
        let phi: Float = u[XYEnum::Y] * self.phi_max;
        let mut p_obj: Point3f = Point3f {
            x: self.radius * phi.cos(),
            y: self.radius * phi.sin(),
            z,
        };
        let mut it: InteractionCommon = InteractionCommon {
            n: self
                .object_to_world
                .transform_normal(&Normal3f {
                    x: p_obj.x,
                    y: p_obj.y,
                    z: 0.0,
                })
                .normalize(),
            ..Default::default()
        };
        if self.reverse_orientation {
            it.n *= -1.0 as Float;
        }
        // reproject _p_obj_ to cylinder surface and compute _p_obj_error_
        let hit_rad: Float = (p_obj.x * p_obj.x + p_obj.y * p_obj.y).sqrt();
        p_obj.x *= self.radius / hit_rad;
        p_obj.y *= self.radius / hit_rad;
        let p_obj_error: Vector3f = Vector3f {
            x: p_obj.x,
            y: p_obj.y,
            z: 0.0,
        }
        .abs()
            * gamma(3_i32);
        it.p = self.object_to_world.transform_point_with_abs_error(
            &p_obj,
            &p_obj_error,
            &mut it.p_error,
        );
        *pdf = 1.0 as Float / self.area();
        it
    }
    pub fn sample_with_ref_point(
        &self,
        iref: &InteractionCommon,
        u: Point2f,
        pdf: &mut Float,
    ) -> InteractionCommon {
        let intr: InteractionCommon = self.sample(u, pdf);
        let mut wi: Vector3f = intr.p - iref.p;
        if wi.length_squared() == 0.0 as Float {
            *pdf = 0.0 as Float;
        } else {
            wi = wi.normalize();
            // convert from area measure, as returned by the Sample()
            // call above, to solid angle measure.
            *pdf *= pnt3_distance_squaredf(&iref.p, &intr.p) / nrm_abs_dot_vec3f(&intr.n, &-wi);
            if (*pdf).is_infinite() {
                *pdf = 0.0 as Float;
            }
        }
        intr
    }
    pub fn pdf_with_ref_point(&self, iref: &dyn Interaction, wi: &Vector3f) -> Float {
        // intersect sample ray with area light geometry
        let ray: Ray = iref.spawn_ray(wi);
        // ignore any alpha textures used for trimming the shape when
        // performing this intersection. Hack for the "San Miguel"
        // scene, where this is used to make an invisible area light.
        let mut t_hit: Float = 0.0;
        let mut isect_light: SurfaceInteraction = SurfaceInteraction::default();
        if self.intersect(&ray, &mut t_hit, &mut isect_light) {
            // convert light sample weight to solid angle measure
            let mut pdf: Float = pnt3_distance_squaredf(iref.get_p(), &isect_light.common.p)
                / (nrm_abs_dot_vec3f(&isect_light.common.n, &-(*wi)) * self.area());
            if pdf.is_infinite() {
                pdf = 0.0 as Float;
            }
            pdf
        } else {
            0.0 as Float
        }
    }
}