feat(shader-ast-stdlib): add guassian blur fns

packages/shader-ast-stdlib/src/index.ts

@@ -59,6 +59,7 @@ export * from "./sdf/torus";
 export * from "./sdf/tri";
 export * from "./sdf/union";
 
+export * from "./tex/blur";
 export * from "./tex/index-coord";
 export * from "./tex/index-uv";
 export * from "./tex/read-index";

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

@@ -0,0 +1,136 @@
+import {
+    add,
+    assign,
+    defn,
+    div,
+    mul,
+    ret,
+    sub,
+    sym,
+    texture,
+    vec2,
+    Vec4Sym
+} from "@thi.ng/shader-ast";
+import { Sampler2DSym, Vec2Sym } from "@thi.ng/shader-ast/api";
+
+/**
+ * Inline function. Computes single blur step for given +/- offset &
+ * weight.
+ *
+ * @param col
+ * @param tex
+ * @param uv
+ * @param off
+ * @param k
+ */
+const singlePass = (
+    col: Vec4Sym,
+    tex: Sampler2DSym,
+    uv: Vec2Sym,
+    off: Vec2Sym,
+    k: number
+) =>
+    assign(
+        col,
+        add(
+            col,
+            mul(add(texture(tex, add(uv, off)), texture(tex, sub(uv, off))), k)
+        )
+    );
+
+/**
+ * 5x5 gaussian blur texture lookup, optimized, but based on:
+ *
+ * - http://rastergrid.com/blog/2010/09/efficient-gaussian-blur-with-linear-sampling/
+ * - https://github.com/Jam3/glsl-fast-gaussian-blur
+ *
+ * @param tex sampler2D
+ * @param res resolution
+ * @param uv
+ * @param dir blur pass direction (`vec2(1,0)` or `vec2(0,1)`)
+ */
+export const blur5 = defn(
+    "vec4",
+    "blur5",
+    ["sampler2D", "vec2", "vec2", "vec2"],
+    (tex, res, uv, dir) => {
+        let col: Vec4Sym;
+        let off: Vec2Sym;
+        const k1 = 0.29411764705882354;
+        const k2 = 0.35294117647058826;
+        return [
+            (off = sym(div(mul(vec2(1 + 1 / 3), dir), res))),
+            (col = sym(mul(texture(tex, uv), k1))),
+            singlePass(col, tex, uv, off, k2),
+            ret(col)
+        ];
+    }
+);
+
+/**
+ * 9x9 gaussian blur texture lookup, optimized, but based on:
+ *
+ * - http://rastergrid.com/blog/2010/09/efficient-gaussian-blur-with-linear-sampling/
+ * - https://github.com/Jam3/glsl-fast-gaussian-blur
+ *
+ * @param tex sampler2D
+ * @param res resolution
+ * @param uv
+ * @param dir blur pass direction (`vec2(1,0)` or `vec2(0,1)`)
+ */
+export const blur9 = defn(
+    "vec4",
+    "blur9",
+    ["sampler2D", "vec2", "vec2", "vec2"],
+    (tex, res, uv, dir) => {
+        let col: Vec4Sym;
+        let off: Vec2Sym;
+        let off2: Vec2Sym;
+        const k1 = 0.3162162162;
+        const k2 = 0.0702702703;
+        return [
+            (off = sym(div(mul(vec2(1.3846153846), dir), res))),
+            (off2 = sym(div(mul(vec2(3.2307692308), dir), res))),
+            (col = sym(mul(texture(tex, uv), 0.227027027))),
+            singlePass(col, tex, uv, off, k1),
+            singlePass(col, tex, uv, off2, k2),
+            ret(col)
+        ];
+    }
+);
+
+/**
+ * 13x13 gaussian blur texture lookup, optimized, but based on:
+ *
+ * - http://rastergrid.com/blog/2010/09/efficient-gaussian-blur-with-linear-sampling/
+ * - https://github.com/Jam3/glsl-fast-gaussian-blur
+ *
+ * @param tex sampler2D
+ * @param res resolution
+ * @param uv
+ * @param dir blur pass direction (`vec2(1,0)` or `vec2(0,1)`)
+ */
+export const blur13 = defn(
+    "vec4",
+    "blur13",
+    ["sampler2D", "vec2", "vec2", "vec2"],
+    (tex, res, uv, dir) => {
+        let col: Vec4Sym;
+        let off: Vec2Sym;
+        let off2: Vec2Sym;
+        let off3: Vec2Sym;
+        const k1 = 0.2969069646728344;
+        const k2 = 0.09447039785044732;
+        const k3 = 0.010381362401148057;
+        return [
+            (off = sym(div(mul(vec2(1.411764705882353), dir), res))),
+            (off2 = sym(div(mul(vec2(3.2941176470588234), dir), res))),
+            (off3 = sym(div(mul(vec2(5.176470588235294), dir), res))),
+            (col = sym(mul(texture(tex, uv), 0.1964825501511404))),
+            singlePass(col, tex, uv, off, k1),
+            singlePass(col, tex, uv, off2, k2),
+            singlePass(col, tex, uv, off3, k3),
+            ret(col)
+        ];
+    }
+);