Fix gsplat example (playcanvas#6754)

examples/src/examples/loaders/gsplat-many.shader.vert

@@ -1,19 +1,44 @@
 uniform float uTime;
 varying float height;
 
+void animate() {
+    // modify center
+    float heightIntensity = center.y * 0.2;
+    center.x += sin(uTime * 5.0 + center.y) * 0.3 * heightIntensity;
+
+    // output y-coordinate
+    height = center.y;
+}
+
+vec4 discardVec = vec4(0.0, 0.0, 2.0, 1.0);
+
 void main(void)
 {
-    // evaluate center of the splat in object space
-    vec3 centerLocal = evalCenter();
+    // calculate splat uv
+    if (!calcSplatUV()) {
+        gl_Position = discardVec;
+        return;
+    }
 
-    // modify it
-    float heightIntensity = centerLocal.y * 0.2;
-    centerLocal.x += sin(uTime * 5.0 + centerLocal.y) * 0.3 * heightIntensity;
+    // read data
+    readData();
 
-    // output y-coordinate
-    height = centerLocal.y;
+    // animate
+    animate();
+
+    vec4 pos;
+    if (!evalSplat(pos)) {
+        gl_Position = discardVec;
+        return;
+    }
+
+    gl_Position = pos;
+
+    texCoord = vertex_position.xy;
+    color = getColor();
+
+    #ifndef DITHER_NONE
+        id = float(splatId);
+    #endif
 
-    // evaluate the rest of the splat using world space center
-    vec4 centerWorld = matrix_model * vec4(centerLocal, 1.0);
-    gl_Position = evalSplat(centerWorld);
 }