Overcoming Technical Limitations In Isometric Games
Rendering Smooth Movement and Diagonal Pathfinding
A core challenge in isometric games is enabling smooth diagonal character movement and pathfinding. Since isometric grids use diamond-shaped tiles, moving diagonally requires calculating paths along both the x and y axes. This can result in jerky movement if not handled carefully in code.
One solution is to implement raycasting when determining available paths. This involves projecting imaginary rays from the character’s location and testing for collisions. Any open paths can then be smoothed using algorithms like Simple Smooth or Polynomial Smooth. These interpolate additional movement points to round off harsh diagonals into natural curves.
Sample A* Pathfinding Implementation for Isometric Grids
The A* algorithm can be adapted to handle pathfinding in isometric spaces. Here is some sample C# code:
public class IsometricAStarPathfinder {
// Diamond coordinate offsets
int[] dx = new int[] {-1, 0, 1, -1, 1, -1, 0, 1};
int[] dy = new int[] {0, -1, 0, 1, 1, -1, -1, 1};
public List FindPath(Vector2 start, Vector2 end) {
// Usual A* setup and heuristics here
openSet.Add(start);
// Main pathfinding loop
while (openSet.Count > 0) {
// Get lowest F cost node as current
current = GetLowestFCost(openSet);
// Check if we reached end
if (current == end) {
return BuildPath(cameFrom, current);
}
// Loop through diamond neighbors
for (int i = 0; i < 8; ++i) {
// Get neighbor position
neighbor.x = current.x + dx[i];
neighbor.y = current.y + dy[i];
// Validate and calculate cost
// ...
// Update neighbor data
// ...
}
}
// No path found
return null;
}
}
This allows units to move smoothly along diagonals by considering two axis increments at once. The core A* logic remains the same even though it now handles diamond tiles.
Faking Perspective Depth
Unlike full 3D, isometric graphics lack a real sense of depth and perspective. Clever visual tricks can help suggest depth to make the world feel richer.
Sorting sprite render order is a quick way to push assets back. SpriteRenderers can be sorted by their y position, with higher tiles rendered on top to simulate foreground layering. Lighting also impacts perceived depth - foreground elements can cast shadows onto the background.
Environment decoration can also sell depth without much work. Distant trees, roads, and buildings subtly reinforce distance. The same goes for detail reduction and fade-out fog effects. Parallax techniques shift assets at different rates to create fake depth too.
Shader Code for Faked Parallax Occlusion
Here is some example shader code for applying a parallax occlusion mapping effect in Unity:
Shader "Custom/Parallax" {
Properties {
_MainTex ("Base Texture", 2D) = "" {}
_Bump ("Normalmap", 2D) = "" {}
_Height ("Height", Range(0, 0.1)) = 0.05
// Other properties
}
SubShader {
Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
uniform sampler2D _MainTex;
uniform sampler2D _Bump;
uniform float _Height;
struct VertexInput {
float4 vertex : POSITION;
float2 tex : TEXCOORD0;
};
struct VertexOutput {
float4 pos : SV_POSITION;
float2 tex : TEXCOORD0;
float3 viewDir;
};
VertexOutput vert(VertexInput input) {
VertexOutput o;
// Calculations
o.viewDir = ObjSpaceViewDir(input.vertex);
return o;
}
float4 frag(VertexOutput output) : COLOR {
float height = tex2D(_Bump, output.tex).r;
output.tex += (height - 0.5) * _Height * output.viewDir.xy / output.viewDir.z;
return tex2D(_MainTex, output.tex);
}
ENDCG
}
}
}
This shifts the texture sampling coordinates based on view angle and bump map height to create a convincing depth effect. It works very well for rocky surfaces and brickwork.
Working Around Restricted Camera Controls
Unlike full 3D games, isometric cameras cannot be freely rotated or positioned. This significantly limits what areas are visible to the player. There are ways to mitigate the effects though.
Panning helps open up the field of view so more map tiles become navigable without watching the character walk. Automatic screen edge panning when the mouse hits window bounds keeps attention focused ahead. Zooming in and out also reveals more around the player.
Vignetting and offset cameras can shift off-center tiles into better view too. This helps peek around foreground blocking and open up playable space.
Adding Mouse-Drag Panning in Unity
Here is some C# code to enable mouse panning of an isometric camera in Unity:
public class IsoCameraController : MonoBehaviour {
public float panSpeed = 10f;
private Vector3 dragOrigin;
void Update() {
// Pan on mouse drag
if(Input.GetMouseButtonDown(0)) {
dragOrigin = Input.mousePosition;
} else if(Input.GetMouseButton(0)) {
Vector3 pos = Camera.main.ScreenToViewportPoint(Input.mousePosition - dragOrigin);
Vector3 move = new Vector3(pos.x * panSpeed, pos.y * panSpeed, 0);
transform.Translate(move, Space.World);
}
}
}
Now clicking and dragging across the game view will smoothly pan the camera. Edge of screen input can trigger automated panning too for extended visibility.
Optimizing Performance With Occlusion Culling
Isometric games feature highly detailed static environments full of objects. Rendering all that visual data drags down performance fast. Occlusion culling improves speed by hiding anything outside the camera view.
On tilemaps, individual room or city block tiles can be occlusion tested against view frustums. If a tile falls outside, its Renderer is disabled to skip drawing costly assets.
Discrete objects like props can batch together in occlusion zones that themselves cull off. Hiding zones skips all their contents at once without testing each item.
Basic Occlusion Culling for Tilemaps
Here is a basic Unity occlusion system tailored for 2D isometric tilemap rooms:
public class TileOcclusionCulling : MonoBehaviour {
public MapGenerator map;
void OnBecameVisible() {
// Enable tile renderers in view
}
void OnBecameInvisible() {
// Disable tile renderers outside view
}
void CheckVisibility() {
Bounds viewBounds = Camera.main.ViewportToWorldPoint(new Bounds(0,0,1,1));
for(int i = 0; i < map.rooms.Length; i++) {
if(viewBounds.Intersects(map.rooms[i].Bounds)) {
map.rooms[i].EnableRenderers();
}
else {
map.rooms[i].DisableRenderers();
}
}
}
}
Wrapping tile groups into room prefabs with a bounds check speeds up occlusion testing and avoids checking hundreds of individual tiles.
Streamlining Assets Without Losing Quality
Detailed 2D art requires significant production work that can limit scope. Procedural techniques multiply smaller asset sets into vast environments without supreme effort.
Interchangeable texture swaps and recolors on sprite prefabs create identifiable variants. Parts of sprites can also swap via code - this outfits characters and architecture endlessly via modular pieces.
background set dressing like fans, pipes, vines etc overlay modular walls easily. Prefab mesh combines attach prop assets into walls for natural integration and variety.
Environment Generation Script
Here is a C# script for randomly generating isometric room interiors by drawing from asset pools:
public class RoomGenerator : MonoBehaviour {
public Transform tilemap;
public SpriteRenderer wallPrefab;
public SpriteRenderer[] floorPrefabs;
public SpriteRenderer[] props;
public void Generate() {
// Instantiate floor
int rand = Random.Range(0, floorPrefabs.Length);
SpriteRenderer floor = Instantiate(floorPrefabs[rand], tilemap);
// Make walls
SpriteRenderer north = Instantiate(wallPrefab, tilemap);
north.transform.position += Vector3.up;
SpriteRenderer south = Instantiate(wallPrefab, tilemap);
south.transform.position += Vector3.down;
// Spawn props
for(int i = 0; i < Random.Range(2, 8); i++) {
SpriteRenderer prop = Instantiate(props[Random.Range(0, props.Length)];
prop.transform.SetParent(tilemap);
prop.transform.position += Random.insideUnitCircle;
}
}
}
This allows building interiors to rapidly generate with optional detached prop assets bringing them to life. The modular props, walls, and floors shuffle for natural variety.
