I put this together based on free tutorials and parts of other free scripts (no paid assets were used) I found online, so rather than post on asset store to make a few $$$… I figured it was fair to share with the community, and make save someone else some time or teach them something.
It’s just a real simple 2D water line script, ideal for a cartoon style side-scroller. The main reason I wrote it myself was the ones I found in other places mostly used 3D colliders/physics, or used 100s of game objects, or had issues trying to place them where you want or be able to see how they look in edit mode. This one draws itself in edit mode, only uses 1 game object, and I think should run very fast, even for mobile.
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
[ExecuteInEditMode]
[RequireComponent(typeof(MeshFilter))]
publicclassSimple2DWater : MonoBehaviour
{
// Set to height of water in game units
publicfloat height = 5;
// Set to width of water in game units
publicfloat width = 5;
// Increase for smoother looking water, decrease for faster performance
publicfloat pointsPerUnit = 10;
// When using in edit mode, these track changes to public properites for automatic rebuilding
#if UNITY_EDITOR
float prevHeight;
float prevWidth;
float prevPointsPerUnit;
#endif
// Required component, you should also have a Mesh Renderer if you want to see the water
// I use a 2 pixel wide texture -- just simple vertical gradient with alpha channel and unlit/transparent render
MeshFilter meshFilter;
// Keep track of some physics info for each point
float[] velocities;
float[] accelerations;
float[] leftDeltas;
float[] rightDeltas;
// Our point count, set by Build, just store here because used a lot.
int pointCount;
// Some constants, you may need to adjust.
constfloat springConstant = 0.02f;
constfloat damping = 0.04f;
constfloat spread = 0.05f;
// Build in OnEnable/Awake... OnEnable works better at design-time (edit mode), Awake better for game/play mode.
#if UNITY_EDITOR
void OnEnable()
#else
void Awake()
#endif
{
Build();
}
// Create very simple tris for our mesh.
int[] GetMeshTriangles(Vector3[] verts)
{
int[] triangles = newint[verts.Length * 3];
for (int i = 0; i < verts.Length - 3; i += 2)
{
int t = i * 3;
triangles[t] = i;
triangles[t + 1] = i + 1;
triangles[t + 2] = i + 3;
triangles[t + 3] = i + 3;
triangles[t + 4] = i + 2;
triangles[t + 5] = i;
}
return triangles;
}
// Create very simple UVs for our mesh.
Vector2[] GetUVMapping(Vector3[] verts)
{
Vector2[] uvs = newVector2[verts.Length];
for (int i = 0; i < verts.Length; i++)
{
float xMapping;
float yMapping;
if (i % 2 == 0)
{
yMapping = 0;
xMapping = 0;
}
else
{
yMapping = 1;
xMapping = 1;
}
uvs[i] = newVector2(xMapping, yMapping);
}
return uvs;
}
// Build our mesh, only done once in game mode, in edit mode rebuilds if public properties change.
publicvoid Build()
{
meshFilter = GetComponent<MeshFilter>();
// Calculate number of points based on public properties
pointCount = Mathf.CeilToInt(width * pointsPerUnit);
if (pointCount < 1)
return;
// Calculate units per point
float unitsPerPoint = width / (float)pointCount;
// Add one extra point for the end
pointCount++;
// Create our arrays just once
velocities = newfloat[pointCount];
accelerations = newfloat[pointCount];
leftDeltas = newfloat[pointCount];
rightDeltas = newfloat[pointCount];
// Initialize all mesh verts, we just use 0 base, you can move the transform around as needed to position mesh in game
Vector3[] verts = newVector3[pointCount * 2];
for (int i = 0; i < pointCount; i++)
{
verts[i * 2].x = i * unitsPerPoint;
verts[i * 2].y = -height;
verts[i * 2].z = 0;
verts[(i * 2) + 1].x = i * unitsPerPoint;
verts[(i * 2) + 1].y = 0;
verts[(i * 2) + 1].z = 0;
}
// Assign mesh to MeshFilter and create some basic tris and UVs
Mesh mesh = newMesh();
mesh.vertices = verts;
mesh.triangles = GetMeshTriangles(verts);
mesh.uv = GetUVMapping(verts);
mesh.RecalculateBounds();
mesh.RecalculateNormals();
GameObject.DestroyImmediate(meshFilter.sharedMesh);
meshFilter.sharedMesh = mesh;
}
// I use fixed update since I plan on adding some extra physics here, and Unity says that should be done in FixedUpdate (not Update).
void FixedUpdate()
{
if (pointCount < 1)
return;
// You can use this for testing, will apply a splash on click, based on current mouse position.
// This is a good place to try different velocity values to see what works best with your setup.
#if false
if (Input.GetMouseButtonDown(0))
{
Vector3 inputPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
Splash(inputPos.x, 5f);
Debug.Log("Splash: " + inputPos.x);
}
#endif
// Get verts from our mesh
Vector3[] verts = meshFilter.sharedMesh.vertices;
// Apply splash from contact by other objects.
// For each point except the last...
for (int i = 0; i < pointCount - 1; i++)
{
Vector2 v1 = verts[(i * 2) + 1];
v1 = transform.TransformPoint(v1);
Vector2 v2 = verts[((i + 1) * 2) + 1];
v2 = transform.TransformPoint(v2);
// Check for objects between points.
RaycastHit2D hit = Physics2D.Linecast(v1, v2);
if (hit.rigidbody == null)
continue;
// If object found, apply splash. You may need to adjust the velocity part.
//Debug.Log(hit.rigidbody.gameObject);
Splash(hit.point.x, hit.rigidbody.velocity.y / 20f);
}
// Apply damping, velocity, and acceleration.
for (int i = 0; i < pointCount; i++)
{
float y = verts[(i * 2) + 1].y;
float force = springConstant * y + velocities[i] * damping;
accelerations[i] = -force;
y += velocities[i];
velocities[i] += accelerations[i];
verts[(i * 2) + 1].y = y;
}
// Apply wave motion (adjust adjacent points), uses multiple passes for more realistic motion.
for (int j = 0; j < 8; j++)
{
for (int i = 0; i < pointCount; i++)
{
float y = verts[(i * 2) + 1].y;
if (i > 0)
{
float prevY = verts[((i - 1) * 2) + 1].y;
leftDeltas[i] = spread * (y - prevY);
velocities[i - 1] += leftDeltas[i];
}
if (i < pointCount - 1)
{
float nextY = verts[((i + 1) * 2) + 1].y;
rightDeltas[i] = spread * (y - nextY);
velocities[i + 1] += rightDeltas[i];
}
}
}
// Update verts based on wave motion we calculated above.
for (int i = 0; i < pointCount; i++)
{
if (i > 0)
{
verts[((i - 1) * 2) + 1].y += leftDeltas[i];
}
if (i < pointCount - 1)
{
verts[((i + 1) * 2) + 1].y += rightDeltas[i];
}
}
// Apply updates to mesh
meshFilter.sharedMesh.vertices = verts;
}
// Cause a splash!
void Splash(float xpos, float velocity)
{
//Debug.Log("Splash: " + velocity);
if (pointCount < 1)
return;
xpos = transform.InverseTransformPoint(xpos, 0, 0).x;
// If xpos is left or right of water, we just treat as end of water, you could ignore the hit
// instead, if you want.
float unitsPerPoint = width / (float)pointCount;
int pointIndex = Mathf.RoundToInt(xpos / unitsPerPoint);
if (pointIndex < 0)
pointIndex = 0;
elseif (pointIndex >= pointCount)
pointIndex = pointCount - 1;
Debug.Log("Splash: " + pointIndex + " " + velocity);
// Just set the velocity of the point that was hit.
velocities[pointIndex] = velocity;
}
// This only runs in edit mode (design-time) and just rebuilds our mesh anytime public properties change.
#if UNITY_EDITOR
void OnRenderObject()
{
bool changed = false;
if (prevHeight != height ||
prevWidth != width ||
prevPointsPerUnit != pointsPerUnit)
changed = true;
if (changed)
{
Build();
UnityEditor.SceneView.RepaintAll();
prevHeight = height;
prevWidth = width;
prevPointsPerUnit = pointsPerUnit;
}
}
#endif
}
Usage steps that work for me in latest version of Unity:
-
Add a script to your project, Simple2DWater.cs, and replace the entire contents with the script above.
-
Place an empty game object on your scene
-
Add the above script to it, it should auto add the required MeshFilter
-
Add a MeshRenderer (optional, but you probably want to see the water, eh?) and set it up how you normally would… I’ve only used with real simple textures, I usually just use an image that is 2 pixels wide and a simple vertical gradient – with an alpha channel, translucent, if you want to see through the water. I set the image type to texture and repeat… all basic stuff if you have used a MeshRenderer before.
-
Click Play and start dropping rigid body + collider objects in the water.
I wanted to make this using an EdgeCollider2D instead of the LineCast method, but using a single collider (of any kind) I couldn’t figure out how to detect the point of contact on the water… because the collider needs to be a trigger, and OnTrigger?2D events don’t give contact point info 
I guess with this method, if you really need extra performance and don’t care about less realistic splashing, you could use a single LineCast over the normal surface of the water, instead of checking each segment.
Enjoy!