fix: Lower boundary force further to prevent sticking, decrease extra distance added

Author: 0ffz

particles-kool/src/commonMain/kotlin/me/dvyy/particles/compute/simulation/FieldsShader.kt

@@ -167,14 +167,15 @@ class FieldsShader(
                 // Wall repulsion
                 //TODO make configurable, since lennardJones might not be provided
                 fun lJ(dist: KslExpression<KslFloat1>) = (functions["lennardJones"] as KslFunctionFloat1)
-                    .invoke(dist, 1f.const, 3f.const, 0.002f.const)
-                nextForce.x += lJ(position.x - 0f.const + 1f.const)
-                nextForce.x -= lJ(boxMax.x - position.x + 1f.const)
-                nextForce.y += lJ(position.y - 0f.const + 1f.const)
-                nextForce.y -= lJ(boxMax.y - position.y + 1f.const)
+                    .invoke(dist, 1f.const, 5f.const, 0.0001f.const)
+                val extraDist = 0.1f.const // Add a small amount of distance so the force is always nonzero
+                nextForce.x += lJ(position.x + extraDist)
+                nextForce.x -= lJ(boxMax.x - position.x + extraDist)
+                nextForce.y += lJ(position.y + extraDist)
+                nextForce.y -= lJ(boxMax.y - position.y + extraDist)
                 `if`(boxMax.z ne 0f.const) {
-                    nextForce.z += lJ(position.z - 0f.const + 1f.const)
-                    nextForce.z -= lJ(boxMax.z - position.z + 1f.const)
+                    nextForce.z += lJ(position.z + extraDist)
+                    nextForce.z -= lJ(boxMax.z - position.z + extraDist)
                 }
                 // Cap force
                 `if`(length(nextForce) gt params.maxForce.ksl) {