particle spread

1 files changed, 12 insertions, 0 deletions

diff --git a/src/objs/specks.lua b/src/objs/specks.lua
index 229eb23..485a58a 100644
--- a/src/objs/specks.lua
+++ b/src/objs/specks.lua
@@ -32,6 +32,7 @@ function Speck_Sys.new()
 
   self.initial_velx = 0
   self.initial_vely = 0
+  self.spread = 0
 
   self.lifetime_min = 1
   self.lifetime_max = 5
@@ -81,6 +82,17 @@ function Speck_Sys:update(dt)
     data.pos[id] = { x = self.x, y = self.y }
     data.vel[id] = { x = self.initial_velx, y = self.initial_vely }
 
+    local beta = self.spread * math.pi / 180
+    beta = beta / 2
+    beta = randf_range(-beta, beta)
+
+    local rvx = (data.vel[id].x * math.cos(beta))
+              - (data.vel[id].y * math.sin(beta))
+    local rvy = (data.vel[id].x * math.sin(beta))
+              + (data.vel[id].y * math.cos(beta))
+    data.vel[id].x = rvx
+    data.vel[id].y = rvy
+
     data.lifetime[id] = randf_range(
       self.lifetime_min, self.lifetime_max)
     data.lifetime_max[id] = data.lifetime[id]