patterns: implement object and pattern transformation awareness.

rtchallenge/examples/eoc6.rs

@@ -44,7 +44,15 @@ fn main() -> Result<()> {
                 let point = r.position(hit.t);
                 let normal = hit.object.normal_at(point);
                 let eye = -r.direction;
-                let color = lighting(&hit.object.material, &light, point, eye, normal, in_shadow);
+                let color = lighting(
+                    &hit.object.material,
+                    &hit.object,
+                    &light,
+                    point,
+                    eye,
+                    normal,
+                    in_shadow,
+                );
                 c.set(x, y, color);
             }
         }

rtchallenge/src/materials.rs

@@ -3,6 +3,7 @@ use derive_builder::Builder;
 use crate::{
     lights::PointLight,
     patterns::StripePattern,
+    shapes::Shape,
     tuples::{dot, reflect, Color, Tuple},
     Float, BLACK, WHITE,
 };
@@ -83,6 +84,7 @@ impl Default for Material {
 ///     lights::PointLight,
 ///     materials::{lighting, Material},
 ///     patterns::stripe_pattern,
+///     shapes::Shape,
 ///     tuples::{point, vector, Color},
 ///     Float, BLACK, WHITE,
 /// };
@@ -90,40 +92,41 @@ impl Default for Material {
 /// let in_shadow = false;
 /// let m = Material::default();
 /// let position = point(0., 0., 0.);
+/// let object = Shape::sphere();
 ///
 /// // Lighting with the eye between the light and the surface.
 /// let eyev = vector(0., 0., -1.);
 /// let normalv = vector(0., 0., -1.);
 /// let light = PointLight::new(point(0., 0., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
+/// let result = lighting(&m, &object, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(1.9, 1.9, 1.9));
 ///
 /// // Lighting with the eye between the light and the surface, eye offset 45°.
 /// let eyev = vector(0., (2. as Float).sqrt() / 2., -(2. as Float).sqrt() / 2.);
 /// let normalv = vector(0., 0., -1.);
 /// let light = PointLight::new(point(0., 0., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
+/// let result = lighting(&m, &object, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, WHITE);
 ///
 /// // Lighting with the eye opposite surface, light offset 45°.
 /// let eyev = vector(0., 0., -1.);
 /// let normalv = vector(0., 0., -1.);
 /// let light = PointLight::new(point(0., 10., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
+/// let result = lighting(&m, &object, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(0.7364, 0.7364, 0.7364));
 ///
 /// // Lighting with the eye in the path of the reflection vector.
 /// let eyev = vector(0., -(2.0 as Float).sqrt() / 2., -(2.0 as Float).sqrt() / 2.);
 /// let normalv = vector(0., 0., -1.);
 /// let light = PointLight::new(point(0., 10., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
+/// let result = lighting(&m, &object, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(1.63639, 1.63639, 1.63639));
 ///
 /// // Lighting with the light behind the surface.
 /// let eyev = vector(0., 0., -1.);
 /// let normalv = vector(0., 0., -1.);
 /// let light = PointLight::new(point(0., 0., 10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
+/// let result = lighting(&m, &object, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(0.1, 0.1, 0.1));
 ///
 /// // Lighting with the surface in shadow.
@@ -131,7 +134,7 @@ impl Default for Material {
 /// let eyev = vector(0., 0., -1.);
 /// let normalv = vector(0., 0., -1.);
 /// let light = PointLight::new(point(0., 0., -10.), WHITE);
-/// let result = lighting(&m, &light, position, eyev, normalv, in_shadow);
+/// let result = lighting(&m, &object, &light, position, eyev, normalv, in_shadow);
 /// assert_eq!(result, Color::new(0.1, 0.1, 0.1));
 ///
 /// // Lighting with a pattern applied.
@@ -146,13 +149,30 @@ impl Default for Material {
 /// let eyev = vector(0., 0., -1.);
 /// let normalv = vector(0., 0., -1.);
 /// let light = PointLight::new(point(0., 0., -10.), WHITE);
-/// let c1 = lighting(&m, &light, point(0.9, 0., 0.), eyev, normalv, false);
-/// let c2 = lighting(&m, &light, point(1.1, 0., 0.), eyev, normalv, false);
+/// let c1 = lighting(
+///     &m,
+///     &object,
+///     &light,
+///     point(0.9, 0., 0.),
+///     eyev,
+///     normalv,
+///     false,
+/// );
+/// let c2 = lighting(
+///     &m,
+///     &object,
+///     &light,
+///     point(1.1, 0., 0.),
+///     eyev,
+///     normalv,
+///     false,
+/// );
 /// assert_eq!(c1, WHITE);
 /// assert_eq!(c2, BLACK);
 /// ```
 pub fn lighting(
     material: &Material,
+    object: &Shape,
     light: &PointLight,
     point: Tuple,
     eyev: Tuple,
@@ -162,7 +182,7 @@ pub fn lighting(
     // Combine the surface color with the light's color.
     let color = match &material.color {
         ColorMapper::Constant(color) => *color,
-        ColorMapper::StripePattern(pat) => pat.stripe_at(point),
+        ColorMapper::StripePattern(pat) => pat.stripe_at_object(object, point),
     };
     let effective_color = color * light.intensity;
     // Find the direciton of the light source.

rtchallenge/src/patterns.rs

@@ -1,9 +1,15 @@
-use crate::tuples::{Color, Tuple};
+use crate::{
+    matrices::Matrix4x4,
+    shapes::Shape,
+    tuples::{Color, Tuple},
+};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct StripePattern {
     pub a: Color,
     pub b: Color,
+    transform: Matrix4x4,
+    inverse_transform: Matrix4x4,
 }
 
 /// Create a material pattern that alternates between the given colors along each unit of the
@@ -18,7 +24,12 @@ pub struct StripePattern {
 /// assert_eq!(pattern.b, WHITE);
 /// ```
 pub fn stripe_pattern(a: Color, b: Color) -> StripePattern {
-    StripePattern { a, b }
+    StripePattern {
+        a,
+        b,
+        transform: Matrix4x4::identity(),
+        inverse_transform: Matrix4x4::identity(),
+    }
 }
 
 impl StripePattern {
@@ -64,4 +75,54 @@ impl StripePattern {
             self.b
         }
     }
+    /// Sample the color at the given world point on the given object.
+    /// This function respects the object and the pattern's transform matrix.
+    ///
+    /// # Examples
+    /// ```
+    /// use rtchallenge::{
+    ///     matrices::scaling,
+    ///     patterns::stripe_pattern,
+    ///     shapes::{Shape, ShapeBuilder},
+    ///     tuples::point,
+    ///     BLACK, WHITE,
+    /// };
+    ///
+    /// # fn main() -> Result<(), Box<std::error::Error>> {
+    ///
+    /// // Stripes with an object transformation.
+    /// let object = ShapeBuilder::sphere()
+    ///     .transform(scaling(2., 2., 2.))
+    ///     .build()?;
+    /// let pattern = stripe_pattern(WHITE, BLACK);
+    /// let c = pattern.stripe_at_object(&object, point(1.5, 0., 0.));
+    /// assert_eq!(c, WHITE);
+    ///
+    /// // Stripes with an pattern transformation.
+    /// let object = Shape::sphere();
+    /// let mut pattern = stripe_pattern(WHITE, BLACK);
+    /// pattern.set_transform(scaling(2., 2., 2.));
+    /// let c = pattern.stripe_at_object(&object, point(1.5, 0., 0.));
+    /// assert_eq!(c, WHITE);
+    ///
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn stripe_at_object(&self, object: &Shape, world_point: Tuple) -> Color {
+        let object_point = object.inverse_transform() * world_point;
+        let pattern_point = self.inverse_transform * object_point;
+        self.stripe_at(pattern_point)
+    }
+    pub fn transform(&self) -> Matrix4x4 {
+        self.transform
+    }
+
+    pub fn inverse_transform(&self) -> Matrix4x4 {
+        self.inverse_transform
+    }
+
+    pub fn set_transform(&mut self, t: Matrix4x4) {
+        self.transform = t;
+        self.inverse_transform = t.inverse();
+    }
 }

rtchallenge/src/shapes.rs

@@ -347,6 +347,10 @@ impl Shape {
         self.transform
     }
 
+    pub fn inverse_transform(&self) -> Matrix4x4 {
+        self.inverse_transform
+    }
+
     pub fn set_transform(&mut self, t: Matrix4x4) {
         self.transform = t;
         self.inverse_transform = t.inverse();

rtchallenge/src/world.rs

@@ -141,6 +141,7 @@ impl World {
                 let shadowed = self.is_shadowed(comps.over_point, light);
                 acc + lighting(
                     &comps.object.material,
+                    &comps.object,
                     light,
                     comps.over_point,
                     comps.eyev,