fix(glsl): fix bilinear texture call in sim

Author: MrTelanie

src/glsl/builtin-texture.js

@@ -13,8 +13,8 @@ export class Texture2D {
 
   get(builtIn, pos) {
     const { w, h, bilinear } = this;
-    let x = pos.x * w;
-    let y = pos.y * h;
+    let x = pos.x * w - 0.5;
+    let y = pos.y * h - 0.5;
 
     x = (x + w) % w;
     y = (y + h) % h;

test/glsl/sim.js

@@ -306,7 +306,7 @@ float action(vec2 one, vec2 two) {
 
     const shader = ({ texture, vec2, vec4, sampler2D }) => {
       let bar = vec4((image = sampler2D()) => {
-        return texture(image, vec2(0.0, 0.0));
+        return texture(image, vec2(0.5, 0.5));
       });
       return { bar };
     };