trail renderer (#811)

Content/scripts/trail_renderer.lua

@@ -0,0 +1,58 @@
+killProcesses()  -- stops all running lua coroutine processes
+
+backlog_post("---> START SCRIPT: trail_renderer.lua")
+
+local trail = TrailRenderer()
+trail.SetWidth(0.2)
+trail.SetColor(Vector(10,0.1,0.1,1))
+trail.SetBlendMode(BLENDMODE_ADDITIVE)
+trail.SetSubdivision(100)
+
+-- Trail begins as red:
+trail.AddPoint(Vector(-5,2,-3), 4, Vector(10,0.1,0.1,1))
+trail.AddPoint(Vector(5,1,1), 0.5, Vector(10,0.1,0.1,1))
+trail.AddPoint(Vector(10,5,4), 1.2, Vector(10,0.1,0.1,1))
+trail.AddPoint(Vector(6,8,2), 1, Vector(10,0.1,0.1,1))
+trail.AddPoint(Vector(-6,5,0), 1, Vector(10,0.1,0.1,1))
+-- Trail turn into green:
+trail.AddPoint(Vector(0,2,-5), 1, Vector(0.1,100,0.1,1))
+trail.AddPoint(Vector(1,3,5), 1, Vector(0.1,100,0.1,1))
+trail.AddPoint(Vector(-3,2,8), 1, Vector(0.1,100,0.1,1))
+
+trail.Cut() -- start a new trail without connecting to previous points
+
+-- Last trail segment is blue:
+trail.AddPoint(Vector(-5,0,-2), 1, Vector(0.1,0.1,100,1))
+trail.AddPoint(Vector(5,8,5), 1, Vector(0.1,0.1,100,1))
+
+-- First texture is a circle gradient, this makes the overall trail smooth at the edges:
+local texture = texturehelper.CreateGradientTexture(
+	GradientType.Circular,
+	256, 256,
+	Vector(0.5, 0.5), Vector(0.5, 0),
+	GradientFlags.Inverse,
+	"rrrr"
+)
+trail.SetTexture(texture)
+
+-- Second texture is a linear gradient that will be tiled and animated to achieve stippled look:
+local texture2 = texturehelper.CreateGradientTexture(
+	GradientType.Linear,
+	256, 256,
+	Vector(0.5, 0), Vector(0, 0),
+	GradientFlags.Inverse | GradientFlags.Smoothstep,
+	"rrrr"
+)
+trail.SetTexture2(texture2)
+
+runProcess(function()
+	local scrolling = 0
+	while true do
+		scrolling = scrolling - getDeltaTime()
+		trail.SetTexMulAdd2(Vector(10,1,scrolling,0))
+		DrawTrail(trail)
+		render() -- this loop will be blocked until render tick
+	end
+end)
+
+backlog_post("---> END SCRIPT: trail_renderer.lua")