Add next event estimation

ray-tracing-core/src/math/mod.rs

@@ -2,6 +2,7 @@ pub mod dir3;
 pub mod frame;
 pub mod mat3;
 pub mod pos3;
+pub mod sampling;
 
 pub use dir3::Dir3;
 pub use frame::Frame;

ray-tracing-core/src/math/pos3.rs

@@ -31,6 +31,20 @@ impl Pos3 {
             z: 0.0,
         }
     }
+
+    pub fn from_barycentric(vertices: [Self; 3], coordinates: [Float; 3]) -> Self {
+        Self {
+            x: vertices[0].x() * coordinates[0]
+                + vertices[1].x() * coordinates[1]
+                + vertices[2].x() * coordinates[2],
+            y: vertices[0].y() * coordinates[0]
+                + vertices[1].y() * coordinates[1]
+                + vertices[2].y() * coordinates[2],
+            z: vertices[0].z() * coordinates[0]
+                + vertices[1].z() * coordinates[1]
+                + vertices[2].z() * coordinates[2],
+        }
+    }
 }
 
 impl Sub for Pos3 {

ray-tracing-core/src/math/sampling.rs

@@ -0,0 +1,8 @@
+use crate::prelude::*;
+
+/// Sample a triangle
+pub fn sample_triangle(uv: [Float; 2]) -> [Float; 3] {
+    let s = 1.0 - Float::sqrt(1.0 - uv[0]);
+    let t = (1.0 - s) * uv[1];
+    [s, t, 1.0 - s - t]
+}

ray-tracing-core/src/scene.rs

@@ -2,6 +2,13 @@ use crate::prelude::*;
 
 pub trait Scene<R: Rng> {
     fn intersect(&self, ray: Ray, min: Float, max: Float) -> Option<Intersection<'_, R>>;
+
+    fn sample_light(
+        &self,
+        w_in: Dir3,
+        intersection: &Intersection<'_, R>,
+        rng: &mut R,
+    ) -> Option<LightSample<'_, R>>;
 }
 
 pub struct Intersection<'sc, R: Rng> {
@@ -46,3 +53,41 @@ impl<'sc, R: Rng> Intersection<'sc, R> {
         Frame::from_normal(self.normal)
     }
 }
+
+pub struct LightSample<'sc, R: Rng> {
+    pos: Pos3,
+    pdf: Float,
+    normal: Dir3,
+    light: &'sc dyn Light<R>,
+}
+
+impl<'sc, R: Rng> LightSample<'sc, R> {
+    pub fn new(pos: Pos3, pdf: Float, normal: Dir3, light: &'sc dyn Light<R>) -> Self {
+        Self {
+            pos,
+            pdf,
+            normal,
+            light,
+        }
+    }
+
+    pub fn pdf(&self) -> Float {
+        self.pdf
+    }
+
+    pub fn pos(&self) -> Pos3 {
+        self.pos
+    }
+
+    pub fn light(&self) -> &'sc dyn Light<R> {
+        self.light
+    }
+
+    pub fn normal(&self) -> Dir3 {
+        self.normal
+    }
+
+    pub fn tangent_frame(&self) -> Frame {
+        Frame::from_normal(self.normal)
+    }
+}