Bare beginnings of adding bilinear patches.

Mainly as a simple test-case for split-and-dice.

src/surface/bilinear_patch.rs

@@ -0,0 +1,39 @@
+use super::Splitable;
+use crate::math::Point;
+
+#[derive(Debug, Copy, Clone)]
+pub struct BilinearPatch<'a> {
+    time_sample_count: usize,
+
+    // The control points are stored in clockwise order, like this:
+    //  u ----->
+    // v  0  1
+    // |  3  2
+    // \/
+    control_points: &'a [[Point; 4]],
+
+    // Indicates if any of the edges *must* be split, for example if there
+    // are adjacent patches that were split for non-dicing reasons.
+    //
+    // Matching the ascii graph above, the edges are:
+    //
+    //      0
+    //   -------
+    // 3 |     | 1
+    //   -------
+    //      2
+    must_split: [bool; 4],
+}
+
+#[derive(Debug, Copy, Clone)]
+pub struct BilinearSubPatch<'a> {
+    original: &'a BilinearPatch<'a>,
+    clip: [(f32, f32); 4],
+    must_split: [bool; 4],
+}
+
+impl<'a> Splitable for BilinearSubPatch<'a> {
+    fn split(&self /* TODO: splitting criteria. */) -> Option<(Self, Self)> {
+        unimplemented!()
+    }
+}

src/surface/mod.rs

@@ -1,6 +1,7 @@
 #![allow(dead_code)]
 
 // pub mod micropoly_batch;
+pub mod bilinear_patch;
 pub mod micropoly_batch;
 pub mod triangle;
 pub mod triangle_mesh;
@@ -26,6 +27,11 @@ pub trait Surface: Boundable + Debug + Sync {
     );
 }
 
+pub trait Splitable: Copy {
+    /// Splits the surface into two pieces if necessary.
+    fn split(&self /* TODO: splitting criteria. */) -> Option<(Self, Self)>;
+}
+
 #[derive(Debug, Copy, Clone)]
 #[allow(clippy::large_enum_variant)]
 pub enum SurfaceIntersection {