impl Shape for Curve

[wahn]

So far we support only four shapes:

$ rg -trust 'impl Shape' src
src/shapes/disk.rs
75:impl Shape for Disk {

src/shapes/sphere.rs
85:impl Shape for Sphere {

src/shapes/cylinder.rs
76:impl Shape for Cylinder {

src/shapes/triangle.rs
117:impl Shape for Triangle {

For hair we need curves:

Shape "curve" "string type" [ "cylinder" ] "point P" [ ... ] ...

So we have to implement all trait functions:

$ rg -trust 'trait Shape' src -A 15
src/core/shape.rs
8:pub trait Shape {
9-    fn object_bound(&self) -> Bounds3f;
10-    fn world_bound(&self) -> Bounds3f;
11-    fn intersect(&self, r: &Ray) -> Option<(SurfaceInteraction, Float)>;
12-    fn intersect_p(&self, r: &Ray) -> bool;
13-    fn get_reverse_orientation(&self) -> bool;
14-    fn get_transform_swaps_handedness(&self) -> bool;
15-    fn area(&self) -> Float;
16-    fn sample(&self, u: Point2f, pdf: &mut Float) -> InteractionCommon;
17-    fn sample_with_ref_point(&self,
18-                             iref: &InteractionCommon,
19-                             u: Point2f,
20-                             pdf: &mut Float)
21-                             -> InteractionCommon;
22-    fn pdf(&self, iref: &Interaction, wi: Vector3f) -> Float;
23-}

[wahn]

Here is a test scene for straight hair (using curves) rendered by the C++ version:

[wahn]

... and a scene with curly hair:

[wahn]

After commit 008acc6 we get the following panic during rendering the (slightly modified) test scene:

$ ./target/release/examples/pest_test ../../self_hosted/Rust/pbrt/assets/scenes/hair/curly-hair.pbrt
...
BVHAccel::recursive_build(...)
PT88.005236252S seconds for building BVH ...
BVHAccel::flatten_bvh_tree(...)
PT1.191646535S seconds for flattening BVH ...
...
thread '<unnamed>' panicked at 'index out of bounds: the len is 3 but the index is 3', src/shapes/curve.rs:169:60

Memory consumption is pretty high as well ...

[wahn]

Since commit 2f21f43 the curve geometry can be rendered (at least on a laptop with 32GB of memory):

In comparison to the C++ version the curves (using a default matte material for now) are rendered too bright:

We still have to implement Curve::intersect_p(...), but I wait for another machine (with only 12GB of memory, which results in swapping) to finish rendering ...

[wahn]

Commit 3e7dfe7 implements Curve::intersect_p(...) and improves the resulting image:

[wahn]

The geometry part seems to work fine ...