From 054c967e4a06bbbf79359bae701e1b467625839c Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Wed, 9 Sep 2026 22:29:14 -0700
Subject: lighting

---
 src/shader/instance.wgsl | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

(limited to 'src/shader/instance.wgsl')

diff --git a/src/shader/instance.wgsl b/src/shader/instance.wgsl
index a549801..4b921ab 100644
--- a/src/shader/instance.wgsl
+++ b/src/shader/instance.wgsl
@@ -1,8 +1,16 @@
+const AMBIENT_LIGHT = vec4f(0.4, 0.4, 0.4, 1.0);
+const LIGHT_RESOLUTION = 1.0;
+
 struct Camera {
     scale: vec2f,
     centre: vec2f,
 };
 
+struct Lighting {
+    origin: vec2f,
+    _padding: vec2f,
+};
+
 struct Instance {
     centre: vec2f,
     cos_sin: vec2f,
@@ -15,6 +23,9 @@ struct Instance {
 @group(0) @binding(1) var<storage, read> palette: array<vec4f>;
 @group(0) @binding(2) var<storage, read> instances: array<Instance>;
 @group(0) @binding(3) var<storage, read> cells: array<u32>;
+@group(0) @binding(4) var lighting: texture_2d_array<f32>;
+@group(0) @binding(5) var light_sampler: sampler;
+@group(0) @binding(6) var<uniform> light_params: Lighting;
 
 struct VertexOutput {
     @builtin(position) clip_position: vec4f,
@@ -67,5 +78,14 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4f {
         discard;
     }
 
-    return palette[material];
+    var total = vec3f(0.0);
+    let light_dims = vec2f(textureDimensions(lighting));
+    let light_texel = (in.world - light_params.origin) * LIGHT_RESOLUTION;
+    let light_uv = light_texel / light_dims;
+    for (var d = 0u; d < 4u; d++) {
+        total += textureSample(lighting, light_sampler, light_uv, d).rgb;
+    }
+    let light = vec4f(total.r, total.g, total.b, 1.0);
+
+    return palette[material] * (light + AMBIENT_LIGHT);
 }
-- 
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