diff --git a/build.properties b/build.properties
index 5455fea41..97c025135 100644
--- a/build.properties
+++ b/build.properties
@@ -1,7 +1,7 @@
 minecraft.version=1.8
 forge.version=11.14.1.1354
 
-oc.version=1.5.6
+oc.version=1.5.7
 oc.subversion=dev
 
 ae2.version=rv2-beta-22
diff --git a/src/main/resources/application.conf b/src/main/resources/application.conf
index db5fecc34..70fc15b86 100644
--- a/src/main/resources/application.conf
+++ b/src/main/resources/application.conf
@@ -1045,6 +1045,11 @@ opencomputers {
       # Whether Chamelium is edible or not. When eaten, it gives a (short)
       # invisibility buff, and (slightly longer) blindness debuff.
       chameliumEdible: true
+
+      # The maximum light level a printed block can emit. This defaults to
+      # a value similar to that of a redstone torch, because by default the
+      # material prints are made of contains redstone, but no glowstone.
+      maxPrintLightLevel: 8
   }
 
   # Settings for mod integration (the mod previously known as OpenComponents).
diff --git a/src/main/resources/assets/opencomputers/loot/OpenOS/bin/lua.lua b/src/main/resources/assets/opencomputers/loot/OpenOS/bin/lua.lua
index 7265a9c3f..d1176b111 100644
--- a/src/main/resources/assets/opencomputers/loot/OpenOS/bin/lua.lua
+++ b/src/main/resources/assets/opencomputers/loot/OpenOS/bin/lua.lua
@@ -27,12 +27,77 @@ if #args == 0 or options.i then
       return module
     end
   end
-  setmetatable(env, {__index = function(t, k)
-    return _ENV[k] or optrequire(k)
-  end})
+  setmetatable(env, {
+    __index = function(t, k)
+      _ENV[k] = _ENV[k] or optrequire(k)
+      return _ENV[k]
+    end,
+    __pairs = function(self)
+      local t = self
+      return function(_, key)
+        local k, v = next(t, key)
+        if not k and t == env then
+          t = _ENV
+          k, v = next(t)
+        end
+        if not k and t == _ENV then
+          t = package.loaded
+          k, v = next(t)
+        end
+        return k, v
+      end
+    end
+  })
 
   local history = {}
 
+  local function findTable(t, path)
+    if type(t) ~= "table" then return nil end
+    if not path or #path == 0 then return t end
+    local name = string.match(path, "[^.]+")
+    for k, v in pairs(t) do
+      if k == name then
+        return findTable(v, string.sub(path, #name + 2))
+      end
+    end
+    local mt = getmetatable(t)
+    if t == env then mt = {__index=_ENV} end
+    if mt then
+      return findTable(mt.__index, path)
+    end
+    return nil
+  end
+  local function findKeys(t, r, prefix, name)
+    if type(t) ~= "table" then return end
+    for k, v in pairs(t) do
+      if string.match(k, "^"..name) then
+        local postfix = ""
+        if type(v) == "function" then postfix = "()"
+        elseif type(v) == "table" and getmetatable(v) and getmetatable(v).__call then postfix = "()"
+        elseif type(v) == "table" then postfix = "."
+        end
+        table.insert(r, prefix..k..postfix)
+      end
+    end
+    local mt = getmetatable(t)
+    if t == env then mt = {__index=_ENV} end
+    if mt then
+      return findKeys(mt.__index, r, prefix, name)
+    end
+  end
+  local function hint(line, index)
+    local path = string.match(line, "[a-zA-Z_][a-zA-Z0-9_.]*$")
+    if not path then return nil end
+    local suffix = string.match(path, "[^.]+$") or ""
+    local prefix = string.sub(path, 1, #path - #suffix)
+    local t = findTable(env, prefix)
+    if not t then return nil end
+    local r = {}
+    findKeys(t, r, string.sub(line, 1, #line - #suffix), suffix)
+    table.sort(r)
+    return r
+  end
+
   component.gpu.setForeground(0xFFFFFF)
   term.write("Lua 5.2.3 Copyright (C) 1994-2013 Lua.org, PUC-Rio\n")
   component.gpu.setForeground(0xFFFF00)
@@ -45,7 +110,7 @@ if #args == 0 or options.i then
     local foreground = component.gpu.setForeground(0x00FF00)
     term.write(tostring(env._PROMPT or "lua> "))
     component.gpu.setForeground(foreground)
-    local command = term.read(history)
+    local command = term.read(history, nil, hint)
     if command == nil then -- eof
       return
     end
diff --git a/src/main/resources/assets/opencomputers/loot/OpenOS/boot/04_component.lua b/src/main/resources/assets/opencomputers/loot/OpenOS/boot/04_component.lua
index c58ca54c0..5c084a5ca 100644
--- a/src/main/resources/assets/opencomputers/loot/OpenOS/boot/04_component.lua
+++ b/src/main/resources/assets/opencomputers/loot/OpenOS/boot/04_component.lua
@@ -10,9 +10,27 @@ local primaries = {}
 
 -- This allows writing component.modem.open(123) instead of writing
 -- component.getPrimary("modem").open(123), which may be nicer to read.
-setmetatable(component, { __index = function(_, key)
-                                      return component.getPrimary(key)
-                                    end })
+setmetatable(component, {
+  __index = function(_, key)
+    return component.getPrimary(key)
+  end,
+  __pairs = function(self)
+    local parent = false
+    return function(_, key)
+      if parent then
+        return next(primaries, key)
+      else
+        local k, v = next(self, key)
+        if not k then
+          parent = true
+          return next(primaries)
+        else
+          return k, v
+        end
+      end
+    end
+  end
+})
 
 function component.get(address, componentType)
   checkArg(1, address, "string")
diff --git a/src/main/scala/li/cil/oc/Settings.scala b/src/main/scala/li/cil/oc/Settings.scala
index 07a2b2759..122fc4a3e 100644
--- a/src/main/scala/li/cil/oc/Settings.scala
+++ b/src/main/scala/li/cil/oc/Settings.scala
@@ -297,6 +297,7 @@ class Settings(val config: Config) {
   val maxPrintComplexity = config.getInt("misc.maxPrinterShapes")
   val printRecycleRate = config.getDouble("misc.printRecycleRate")
   val chameliumEdible = config.getBoolean("misc.chameliumEdible")
+  val maxPrintLightLevel = config.getInt("misc.maxPrintLightLevel") max 0 min 15
 
   // ----------------------------------------------------------------------- //
   // integration
diff --git a/src/main/scala/li/cil/oc/common/block/Print.scala b/src/main/scala/li/cil/oc/common/block/Print.scala
index 91d9aab85..d315aa202 100644
--- a/src/main/scala/li/cil/oc/common/block/Print.scala
+++ b/src/main/scala/li/cil/oc/common/block/Print.scala
@@ -74,6 +74,18 @@ class Print(protected implicit val tileTag: ClassTag[tileentity.Print]) extends
 
   override def isOpaqueCube = false
 
+  override def getLightValue(world: IBlockAccess, pos: BlockPos): Int =
+    world.getTileEntity(pos) match {
+      case print: tileentity.Print => print.data.lightLevel
+      case _ => super.getLightValue(world, pos)
+    }
+
+  override def getLightOpacity(world: IBlockAccess, pos: BlockPos): Int =
+    world.getTileEntity(pos) match {
+      case print: tileentity.Print => (print.data.opacity * 4).toInt
+      case _ => super.getLightOpacity(world, pos)
+    }
+
   override def isVisuallyOpaque = false
 
   override def isFullCube = false
diff --git a/src/main/scala/li/cil/oc/common/item/data/PrintData.scala b/src/main/scala/li/cil/oc/common/item/data/PrintData.scala
index eaf765f0b..f63817e24 100644
--- a/src/main/scala/li/cil/oc/common/item/data/PrintData.scala
+++ b/src/main/scala/li/cil/oc/common/item/data/PrintData.scala
@@ -1,6 +1,7 @@
 package li.cil.oc.common.item.data
 
 import li.cil.oc.Constants
+import li.cil.oc.Settings
 import li.cil.oc.api
 import li.cil.oc.util.ExtendedNBT._
 import net.minecraft.item.ItemStack
@@ -19,34 +20,54 @@ class PrintData extends ItemData {
   var label: Option[String] = None
   var tooltip: Option[String] = None
   var isButtonMode = false
-  var emitRedstone = false
+  var redstoneLevel = 0
   var pressurePlate = false
   val stateOff = mutable.Set.empty[PrintData.Shape]
   val stateOn = mutable.Set.empty[PrintData.Shape]
   var isBeaconBase = false
+  var lightLevel = 0
+
+  def emitRedstone = redstoneLevel > 0
+
+  def opacity = {
+    if (opacityDirty) {
+      opacityDirty = false
+      opacity_ = PrintData.computeApproximateOpacity(stateOn) min PrintData.computeApproximateOpacity(stateOff)
+    }
+    opacity_
+  }
+
+  // lazily computed and stored, because potentially slow
+  private var opacity_ = 0f
+  private var opacityDirty = true
 
   override def load(nbt: NBTTagCompound): Unit = {
     if (nbt.hasKey("label")) label = Option(nbt.getString("label")) else label = None
     if (nbt.hasKey("tooltip")) tooltip = Option(nbt.getString("tooltip")) else tooltip = None
     isButtonMode = nbt.getBoolean("isButtonMode")
-    emitRedstone = nbt.getBoolean("emitRedstone")
+    redstoneLevel = nbt.getInteger("redstoneLevel") max 0 min 15
+    if (nbt.getBoolean("emitRedstone")) redstoneLevel = 15
     pressurePlate = nbt.getBoolean("pressurePlate")
     stateOff.clear()
     stateOff ++= nbt.getTagList("stateOff", NBT.TAG_COMPOUND).map(PrintData.nbtToShape)
     stateOn.clear()
     stateOn ++= nbt.getTagList("stateOn", NBT.TAG_COMPOUND).map(PrintData.nbtToShape)
     isBeaconBase = nbt.getBoolean("isBeaconBase")
+    lightLevel = (nbt.getByte("lightLevel") & 0xFF) max 0 min Settings.get.maxPrintLightLevel
+
+    opacityDirty = true
   }
 
   override def save(nbt: NBTTagCompound): Unit = {
     label.foreach(nbt.setString("label", _))
     tooltip.foreach(nbt.setString("tooltip", _))
     nbt.setBoolean("isButtonMode", isButtonMode)
-    nbt.setBoolean("emitRedstone", emitRedstone)
+    nbt.setInteger("redstoneLevel", redstoneLevel)
     nbt.setBoolean("pressurePlate", pressurePlate)
     nbt.setNewTagList("stateOff", stateOff.map(PrintData.shapeToNBT))
     nbt.setNewTagList("stateOn", stateOn.map(PrintData.shapeToNBT))
     nbt.setBoolean("isBeaconBase", isBeaconBase)
+    nbt.setByte("lightLevel", lightLevel.toByte)
   }
 
   def createItemStack() = {
@@ -57,16 +78,42 @@ class PrintData extends ItemData {
 }
 
 object PrintData {
+  // The following logic is used to approximate the opacity of a print, for
+  // which we use the volume as a heuristic. Because computing the actual
+  // volume is a) expensive b) not necessarily a good heuristic (e.g. a
+  // "dotted grid") we take a shortcut and divide the space into a few
+  // sub-sections, for each of which we check if there's anything in it.
+  // If so, we consider that area "opaque". To compensate, prints can never
+  // be fully light-opaque. This gives a little bit of shading as a nice
+  // effect, but avoid it looking derpy when there are only a few sparse
+  // shapes in the model.
+  private val stepping = 4
+  private val step = stepping / 16f
+  private val invMaxVolume = 1f / (stepping * stepping * stepping)
+
+  def computeApproximateOpacity(shapes: Iterable[PrintData.Shape]) = {
+    var volume = 1f
+    if (shapes.size > 0) for (x <- 0 until 16 / stepping; y <- 0 until 16 / stepping; z <- 0 until 16 / stepping) {
+      val bounds = AxisAlignedBB.fromBounds(
+        x * step, y * step, z * step,
+        (x + 1) * step, (y + 1) * step, (z + 1) * step)
+      if (!shapes.exists(_.bounds.intersectsWith(bounds))) {
+        volume -= invMaxVolume
+      }
+    }
+    volume
+  }
+
   def nbtToShape(nbt: NBTTagCompound): Shape = {
     val aabb =
       if (nbt.hasKey("minX")) {
         // Compatibility with shapes created with earlier dev-builds.
-    val minX = nbt.getByte("minX") / 16f
-    val minY = nbt.getByte("minY") / 16f
-    val minZ = nbt.getByte("minZ") / 16f
-    val maxX = nbt.getByte("maxX") / 16f
-    val maxY = nbt.getByte("maxY") / 16f
-    val maxZ = nbt.getByte("maxZ") / 16f
+        val minX = nbt.getByte("minX") / 16f
+        val minY = nbt.getByte("minY") / 16f
+        val minZ = nbt.getByte("minZ") / 16f
+        val maxX = nbt.getByte("maxX") / 16f
+        val maxY = nbt.getByte("maxY") / 16f
+        val maxZ = nbt.getByte("maxZ") / 16f
         AxisAlignedBB.fromBounds(minX, minY, minZ, maxX, maxY, maxZ)
       }
       else {
diff --git a/src/main/scala/li/cil/oc/common/tileentity/Print.scala b/src/main/scala/li/cil/oc/common/tileentity/Print.scala
index f0f51ea69..92f179f9e 100644
--- a/src/main/scala/li/cil/oc/common/tileentity/Print.scala
+++ b/src/main/scala/li/cil/oc/common/tileentity/Print.scala
@@ -33,7 +33,7 @@ class Print extends traits.TileEntity with traits.RedstoneAware with traits.Rota
     world.playSoundEffect(x + 0.5, y + 0.5, z + 0.5, "random.click", 0.3F, if (state) 0.6F else 0.5F)
     world.markBlockForUpdate(getPos)
     if (data.emitRedstone) {
-      EnumFacing.values().foreach(output(_, if (state) 15 else 0))
+      EnumFacing.values().foreach(output(_, if (state) data.redstoneLevel else 0))
     }
     if (state && data.isButtonMode) {
       world.scheduleUpdate(getPos, blockType, blockType.tickRate(world))
diff --git a/src/main/scala/li/cil/oc/common/tileentity/Printer.scala b/src/main/scala/li/cil/oc/common/tileentity/Printer.scala
index 375939af6..285facf1e 100644
--- a/src/main/scala/li/cil/oc/common/tileentity/Printer.scala
+++ b/src/main/scala/li/cil/oc/common/tileentity/Printer.scala
@@ -104,16 +104,29 @@ class Printer extends traits.Environment with traits.Inventory with traits.Rotat
     result(data.tooltip.orNull)
   }
 
-  @Callback(doc = """function(value:boolean) -- Set whether the printed block should emit redstone when in its active state.""")
+  @Callback(doc = """function(value:boolean or number) -- Set whether the printed block should emit redstone when in its active state.""")
   def setRedstoneEmitter(context: Context, args: Arguments): Array[Object] = {
-    data.emitRedstone = args.checkBoolean(0)
+    if (args.isBoolean(0)) data.redstoneLevel = if (args.checkBoolean(0)) 15 else 0
+    else data.redstoneLevel = args.checkInteger(0) max 0 min 15
     isActive = false // Needs committing.
     null
   }
 
-  @Callback(doc = """function():boolean -- Get whether the printed block should emit redstone when in its active state.""")
+  @Callback(doc = """function():boolean, number -- Get whether the printed block should emit redstone when in its active state.""")
   def isRedstoneEmitter(context: Context, args: Arguments): Array[Object] = {
-    result(data.emitRedstone)
+    result(data.emitRedstone, data.redstoneLevel)
+  }
+
+  @Callback(doc = """function(value:number) -- Set what light level the printed block should have.""")
+  def setLightLevel(context: Context, args: Arguments): Array[Object] = {
+    data.lightLevel = args.checkInteger(0) max 0 min Settings.get.maxPrintLightLevel
+    isActive = false // Needs committing.
+    null
+  }
+
+  @Callback(doc = """function():number -- Get which light level the printed block should have.""")
+  def getLightLevel(context: Context, args: Arguments): Array[Object] = {
+    result(data.lightLevel)
   }
 
   @Callback(doc = """function(value:boolean) -- Set whether the printed block should automatically return to its off state.""")
diff --git a/src/main/scala/li/cil/oc/integration/fmp/PrintPart.scala b/src/main/scala/li/cil/oc/integration/fmp/PrintPart.scala
index 914d14ddd..f22fa1a57 100644
--- a/src/main/scala/li/cil/oc/integration/fmp/PrintPart.scala
+++ b/src/main/scala/li/cil/oc/integration/fmp/PrintPart.scala
@@ -94,6 +94,8 @@ class PrintPart(val original: Option[tileentity.Print] = None) extends SimpleBlo
 
   override def doesTick = false
 
+  override def getLightValue: Int = data.lightLevel
+
   override def getBounds = new Cuboid6(if (state) boundsOn else boundsOff)
 
   override def getOcclusionBoxes = {
@@ -127,7 +129,7 @@ class PrintPart(val original: Option[tileentity.Print] = None) extends SimpleBlo
 
   override def strongPowerLevel(side: Int): Int = weakPowerLevel(side)
 
-  override def weakPowerLevel(side: Int): Int = if (data.emitRedstone && state) 15 else 0
+  override def weakPowerLevel(side: Int): Int = if (data.emitRedstone && state) data.redstoneLevel else 0
 
   // ----------------------------------------------------------------------- //
 
@@ -250,11 +252,11 @@ class PrintPart(val original: Option[tileentity.Print] = None) extends SimpleBlo
   }
 
   protected def computeInput(): Int = {
-    val inner = tile.partList.foldLeft(false)((powered, part) => part match {
-      case print: PrintPart => powered || (print.state && print.data.emitRedstone)
-      case _ => powered
+    val inner = tile.partList.foldLeft(0)((power, part) => part match {
+      case print: PrintPart if print.state && print.data.emitRedstone => math.max(power, print.data.redstoneLevel)
+      case _ => power
     })
-    if (inner) 15 else ForgeDirection.VALID_DIRECTIONS.map(computeInput).max
+    math.max(inner, ForgeDirection.VALID_DIRECTIONS.map(computeInput).max)
   }
 
   protected def computeInput(side: ForgeDirection): Int = {
diff --git a/src/main/scala/li/cil/oc/server/component/DebugCard.scala b/src/main/scala/li/cil/oc/server/component/DebugCard.scala
index 29c4f6db1..4d47bc182 100644
--- a/src/main/scala/li/cil/oc/server/component/DebugCard.scala
+++ b/src/main/scala/li/cil/oc/server/component/DebugCard.scala
@@ -40,6 +40,8 @@ import net.minecraftforge.common.util.FakePlayerFactory
 import net.minecraftforge.fluids.FluidRegistry
 import net.minecraftforge.fluids.FluidStack
 import net.minecraftforge.fluids.IFluidHandler
+import net.minecraftforge.fml.common.Loader
+import net.minecraftforge.fml.common.ModAPIManager
 
 import scala.collection.convert.WrapAsScala._
 import scala.collection.mutable
@@ -110,6 +112,13 @@ class DebugCard(host: EnvironmentHost) extends prefab.ManagedEnvironment {
     result(new DebugCard.PlayerValue(args.checkString(0)))
   }
 
+  @Callback(doc = """function(name:string):boolean -- Get whether a mod or API is loaded.""")
+  def isModLoaded(context: Context, args: Arguments): Array[AnyRef] = {
+    checkEnabled()
+    val name = args.checkString(0)
+    result(Loader.isModLoaded(name) || ModAPIManager.INSTANCE.hasAPI(name))
+  }
+
   @Callback(doc = """function(command:string):number -- Runs an arbitrary command using a fake player.""")
   def runCommand(context: Context, args: Arguments): Array[AnyRef] = {
     checkEnabled()
diff --git a/src/main/scala/li/cil/oc/server/driver/Registry.scala b/src/main/scala/li/cil/oc/server/driver/Registry.scala
index ba3a22f61..b71c2adc4 100644
--- a/src/main/scala/li/cil/oc/server/driver/Registry.scala
+++ b/src/main/scala/li/cil/oc/server/driver/Registry.scala
@@ -45,17 +45,26 @@ private[oc] object Registry extends api.detail.DriverAPI {
 
   override def add(driver: api.driver.Block) {
     if (locked) throw new IllegalStateException("Please register all drivers in the init phase.")
-    if (!blocks.contains(driver)) blocks += driver
+    if (!blocks.contains(driver)) {
+      OpenComputers.log.debug(s"Registering block driver ${driver.getClass.getName}.")
+      blocks += driver
+    }
   }
 
   override def add(driver: api.driver.Item) {
     if (locked) throw new IllegalStateException("Please register all drivers in the init phase.")
-    if (!blocks.contains(driver)) items += driver
+    if (!blocks.contains(driver)) {
+      OpenComputers.log.debug(s"Registering item driver ${driver.getClass.getName}.")
+      items += driver
+    }
   }
 
   override def add(converter: Converter) {
     if (locked) throw new IllegalStateException("Please register all converters in the init phase.")
-    if (!converters.contains(converter)) converters += converter
+    if (!converters.contains(converter)) {
+      OpenComputers.log.debug(s"Registering converter ${converter.getClass.getName}.")
+      converters += converter
+    }
   }
 
   override def driverFor(world: World, pos: BlockPos) =