feat(engine): add point light attenuation

4 files changed, 63 insertions, 2 deletions

diff --git a/engine/fragment.glsl b/engine/fragment.glsl
index 428e87f..a9d192b 100644
--- a/engine/fragment.glsl
+++ b/engine/fragment.glsl
@@ -30,5 +30,10 @@ void main()
 		in_texture_coords
 	);
 
+	float attenuation = calc_attenuation(light, in_frag_pos);
+
+	diffuse_light *= attenuation;
+	specular_light *= attenuation;
+
 	FragColor = vec4((ambient_light + diffuse_light + specular_light), 1.0);
 }
diff --git a/engine/light.glsl b/engine/light.glsl
index 49026ec..04a42f5 100644
--- a/engine/light.glsl
+++ b/engine/light.glsl
@@ -13,14 +13,17 @@ struct Material {
     float shininess;
 }; 
 
-struct Light {
+struct PointLight {
 	vec3 position;
     vec3 diffuse;
     vec3 specular;
+    float constant;
+    float linear;
+    float quadratic;
 }; 
   
 uniform Material material;
-uniform Light light;
+uniform PointLight light;
 
 vec3 calc_ambient_light(in vec2 texture_coords)
 {
@@ -56,4 +59,13 @@ vec3 calc_specular_light(
 	);
 }
 
+float calc_attenuation(in PointLight point_light, in vec3 position)
+{
+	float light_distance = length(point_light.position - position);
+
+	return 1.0 / (point_light.constant + point_light.linear
+		* light_distance + point_light.quadratic
+		* pow(light_distance, 2));
+}
+
 #endif
diff --git a/engine/src/lighting.rs b/engine/src/lighting.rs
index bfc2d9b..ffa2645 100644
--- a/engine/src/lighting.rs
+++ b/engine/src/lighting.rs
@@ -11,6 +11,7 @@ pub struct PointLight
 {
     pub diffuse: Color<f32>,
     pub specular: Color<f32>,
+    pub attenuation_params: AttenuationParams,
 }
 }
 
@@ -29,6 +30,7 @@ impl Default for PointLight
         Self {
             diffuse: Color { red: 0.5, green: 0.5, blue: 0.5 },
             specular: Color { red: 1.0, green: 1.0, blue: 1.0 },
+            attenuation_params: AttenuationParams::default(),
         }
     }
 }
@@ -41,6 +43,27 @@ impl Default for PointLightBuilder
     }
 }
 
+/// Parameters for light [attenuation](https://en.wikipedia.org/wiki/Attenuation).
+#[derive(Debug, Clone)]
+pub struct AttenuationParams
+{
+    pub constant: f32,
+    pub linear: f32,
+    pub quadratic: f32,
+}
+
+impl Default for AttenuationParams
+{
+    fn default() -> Self
+    {
+        Self {
+            constant: 1.0,
+            linear: 0.0,
+            quadratic: 0.0,
+        }
+    }
+}
+
 builder! {
 /// Global light properties.
 #[builder(name = GlobalLightBuilder, derives = (Debug, Clone, Default))]
diff --git a/engine/src/renderer/mod.rs b/engine/src/renderer/mod.rs
index e736165..ad587b5 100644
--- a/engine/src/renderer/mod.rs
+++ b/engine/src/renderer/mod.rs
@@ -389,6 +389,27 @@ fn apply_light(
             .into(),
     );
 
+    gl_shader_program.set_uniform_1fv(
+        cstr!("light.constant"),
+        point_light.map_or(1.0, |(light_source, _)| {
+            light_source.attenuation_params.constant
+        }),
+    );
+
+    gl_shader_program.set_uniform_1fv(
+        cstr!("light.linear"),
+        point_light.map_or(0.0, |(light_source, _)| {
+            light_source.attenuation_params.linear
+        }),
+    );
+
+    gl_shader_program.set_uniform_1fv(
+        cstr!("light.quadratic"),
+        point_light.map_or(0.0, |(light_source, _)| {
+            light_source.attenuation_params.quadratic
+        }),
+    );
+
     gl_shader_program.set_uniform_vec_3fv(
         cstr!("material.ambient"),
         &if material_flags.use_ambient_color {