From a1e164454d8637c2cfc1743e21624f78260369ae Mon Sep 17 00:00:00 2001
From: Jared Miller <jared@smell.flowers>
Date: Wed, 11 Mar 2026 13:23:28 -0400
Subject: [PATCH] Add GPU lookup texture data generation for materials

---
 src/__tests__/materials.test.ts | 47 +++++++++++++++++++++++++++++++++
 src/materials/lookupTexture.ts  | 28 ++++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 src/materials/lookupTexture.ts

diff --git a/src/__tests__/materials.test.ts b/src/__tests__/materials.test.ts
index 503ed36..dbc1304 100644
--- a/src/__tests__/materials.test.ts
+++ b/src/__tests__/materials.test.ts
@@ -1,4 +1,8 @@
 import { describe, expect, test } from "bun:test";
+import {
+    generateColorData,
+    generateLookupData,
+} from "../materials/lookupTexture";
 import { MaterialRegistry } from "../materials/registry";
 import {
     BEHAVIOR_GAS,
@@ -72,3 +76,46 @@ describe("MaterialRegistry", () => {
         expect(() => reg.get(254)).toThrow();
     });
 });
+
+describe("lookup texture generation", () => {
+    test("generates 256-entry property array", () => {
+        const reg = new MaterialRegistry();
+        const data = generateLookupData(reg);
+        expect(data.length).toBe(256 * 4);
+    });
+
+    test("sand properties at correct offset", () => {
+        const reg = new MaterialRegistry();
+        const data = generateLookupData(reg);
+        const sand = reg.getByName("sand")!;
+        const offset = sand.id * 4;
+        expect(data[offset + 0]).toBe(BEHAVIOR_POWDER);
+        expect(data[offset + 1]).toBeCloseTo(1.5);
+        expect(data[offset + 2]).toBeCloseTo(0.1);
+    });
+
+    test("generates 256-entry color array", () => {
+        const reg = new MaterialRegistry();
+        const data = generateColorData(reg);
+        expect(data.length).toBe(256 * 4);
+    });
+
+    test("sand color at correct offset", () => {
+        const reg = new MaterialRegistry();
+        const data = generateColorData(reg);
+        const sand = reg.getByName("sand")!;
+        const offset = sand.id * 4;
+        expect(data[offset + 0]).toBeCloseTo(0.76);
+        expect(data[offset + 1]).toBeCloseTo(0.7);
+        expect(data[offset + 2]).toBeCloseTo(0.5);
+        expect(data[offset + 3]).toBeCloseTo(1.0);
+    });
+
+    test("unregistered ids default to air properties", () => {
+        const reg = new MaterialRegistry();
+        const data = generateLookupData(reg);
+        const offset = 200 * 4;
+        expect(data[offset + 0]).toBe(0);
+        expect(data[offset + 1]).toBe(0);
+    });
+});
diff --git a/src/materials/lookupTexture.ts b/src/materials/lookupTexture.ts
new file mode 100644
index 0000000..73e8519
--- /dev/null
+++ b/src/materials/lookupTexture.ts
@@ -0,0 +1,28 @@
+import type { MaterialRegistry } from "./registry";
+
+// generates flat Float32 array for material properties texture (256x1 RGBA)
+// R: behavior type, G: density, B: hardness, A: angleOfRepose / 90
+export function generateLookupData(registry: MaterialRegistry): Float32Array {
+    const data = new Float32Array(256 * 4);
+    for (const m of registry.all()) {
+        const offset = m.id * 4;
+        data[offset + 0] = m.behavior;
+        data[offset + 1] = m.density;
+        data[offset + 2] = m.hardness;
+        data[offset + 3] = m.angleOfRepose / 90.0;
+    }
+    return data;
+}
+
+// generates flat Float32 array for material color texture (256x1 RGBA)
+export function generateColorData(registry: MaterialRegistry): Float32Array {
+    const data = new Float32Array(256 * 4);
+    for (const m of registry.all()) {
+        const offset = m.id * 4;
+        data[offset + 0] = m.color[0];
+        data[offset + 1] = m.color[1];
+        data[offset + 2] = m.color[2];
+        data[offset + 3] = m.color[3];
+    }
+    return data;
+}