feat(shader-ast-stdlib): add packedNormal2(), refactor normal2()

packages/shader-ast-stdlib/src/tex/normal.ts

@@ -1,15 +1,44 @@
-import type { Sampler2DSym, Vec2Sym, Vec2Term } from "@thi.ng/shader-ast";
+import type {
+	Sampler2DSym,
+	TaggedFn1,
+	Vec2Sym,
+	Vec2Term,
+} from "@thi.ng/shader-ast";
 import { F, S2D, V2, V3 } from "@thi.ng/shader-ast/api/types";
 import { defn, ret } from "@thi.ng/shader-ast/ast/function";
 import { vec2, vec3 } from "@thi.ng/shader-ast/ast/lit";
 import { add, sub } from "@thi.ng/shader-ast/ast/ops";
-import { sym } from "@thi.ng/shader-ast/ast/sym";
 import { $x, $y } from "@thi.ng/shader-ast/ast/swizzle";
+import { sym } from "@thi.ng/shader-ast/ast/sym";
 import { normalize } from "@thi.ng/shader-ast/builtin/math";
 import { texture } from "@thi.ng/shader-ast/builtin/texture";
+import { unpackFloat } from "../math/pack-float.js";
+
+/** @internal */
+const __defNormal2 = (decode: TaggedFn1<"vec4", "float">) =>
+	defn(V3, null, [S2D, V2, V2, F, F], (tex, uv, step, z, eps) => {
+		let sx: Vec2Sym;
+		let sy: Vec2Sym;
 
-const sample1 = (tex: Sampler2DSym, uv: Vec2Sym, unit: Vec2Term) =>
-	sub($x(texture(tex, sub(uv, unit))), $x(texture(tex, add(uv, unit))));
+		const sample1 = (tex: Sampler2DSym, uv: Vec2Sym, unit: Vec2Term) =>
+			sub(
+				decode(texture(tex, sub(uv, unit))),
+				decode(texture(tex, add(uv, unit)))
+			);
+
+		return [
+			(sx = sym(vec2($x(step), 0))),
+			(sy = sym(vec2(0, $y(step)))),
+			ret(
+				normalize(
+					add(
+						vec3(sample1(tex, uv, sx), sample1(tex, uv, sy), z),
+						eps
+					)
+				)
+			),
+		];
+	});
 
 /**
  * Computes the surface normal from a grayscale texture at given `uv` position
@@ -27,24 +56,18 @@ const sample1 = (tex: Sampler2DSym, uv: Vec2Sym, unit: Vec2Term) =>
  * @param z
  * @param eps
  */
-export const normal2 = defn(
-	V3,
-	null,
-	[S2D, V2, V2, F, F],
-	(tex, uv, step, z, eps) => {
-		let sx: Vec2Sym;
-		let sy: Vec2Sym;
-		return [
-			(sx = sym(vec2($x(step), 0))),
-			(sy = sym(vec2(0, $y(step)))),
-			ret(
-				normalize(
-					add(
-						vec3(sample1(tex, uv, sx), sample1(tex, uv, sy), z),
-						eps
-					)
-				)
-			),
-		];
-	}
-);
+export const normal2 = __defNormal2(<any>$x);
+
+/**
+ * Principally the same as {@link normal2}, but using a RGBA 8bit/channel
+ * texture storing float values encoded using {@link packFloat}. WHen
+ * `packedNormal2()` then samples this textures, each value will be
+ * automatically decoded using {@link unpackFloat}.
+ *
+ * @param tex
+ * @param uv
+ * @param step
+ * @param z
+ * @param eps
+ */
+export const packedNormal2 = __defNormal2(unpackFloat);