How to implement efficient Fog of War?
- by Cambrano
I've asked a question how to implement Fog Of War(FOW) with shaders. Well I've got this working. I use the vertex color to identify the alpha of a single vertex.
I guess the most of you know what the FOW of Age of Empires was like, anyway I'll shortly explain it:
You have a map. Everything is unexplored(solid black / 100% transparency) at the beginning. When your NPC's / other game units explore the world (by moving around mostly) they unshadow the map. That means. Everything in a specific radius (viewrange) around a NPC is visible (0%transparency). Anything that is out of viewrange but already explored is visible but shadowed (50% transparency).
So yeah, AoE had relatively huge maps. Requirements was something around 100mhz etc. So it should be relatively easy to implement something to solve this problem - actually.
Okay. I'm currently adding planes above my world and set the color per vertex. Why do I use many planes ? Unity has a vertex limit of 65.000 per mesh. According to the size of my tiles and the size of my map I need more than one plane. So I actually need a lot of planes. This is obviously pita for my FPS.
Well so my question is, what are simple (in sense of performance) techniques to implement a FOW shader?
Okay some simplified code what I'm doin so far:
// Setup
for (int x = 0; x < (Map.Dimension/planeSize); x++) {
for (int z = 0; z < (Map.Dimension/planeSize); z++) {
CreateMeshAt(x*planeSize, 3, z*planeSize)
}
}
// Explore (is called from NPCs when walking for example)
for (int x = ((int) from.x - radius); x < from.x + radius; x ++) {
for (int z = ((int) from.z - radius); z < from.z + radius; z ++) {
if (from.Distance(x, 1, z) > radius) continue;
_transparency[x/tileSize, z/tileSize] = 0.5f;
}
}
// Update
foreach(GameObject plane in planes){
foreach(Vector3 vertex in vertices){
Vector3 worldPos = GetWorldPos(vertex);
vertex.Color = new Color(0,0,0, _transparency[worldPos.x/tileSize, worldPos.z/tileSize]);
}
}
My shader just sets the transparency of the vertex now, which comes from the vertex color channel
