Mimic screen text fading for holograms.

Performance might be affected (definitely improved but I can't notice it)

src/main/resources/reference.conf

@@ -66,6 +66,12 @@ opencomputers {
       # hologram projector when at maximum scale. Render distance is scaled
       # down with the actual scale of the hologram.
       hologramRenderDistance: 64
+
+      # The distance at which to start fading out the hologram (as with
+      # hologramRenderDistance). This is purely cosmetic, to avoid image
+      # disappearing instantly when moving too far away from a projector.
+      # It does not affect performance. Holograms are transparent anyway.
+      hologramFadeStartDistance: 48
   }
 
   # Computer related settings, concerns server performance and security.

src/main/scala/li/cil/oc/Settings.scala

@@ -31,6 +31,7 @@ class Settings(config: Config) {
   val robotLabels = config.getBoolean("client.robotLabels")
   val soundVolume = config.getDouble("client.soundVolume").toFloat max 0 min 2
   val fontCharScale = config.getDouble("client.fontCharScale") max 0.5 min 2
+  val hologramFadeStartDistance = config.getDouble("client.hologramFadeStartDistance") max 0
   val hologramRenderDistance = config.getDouble("client.hologramRenderDistance") max 0
 
   // ----------------------------------------------------------------------- //

src/main/scala/li/cil/oc/client/renderer/tileentity/HologramRenderer.scala

@@ -34,6 +34,11 @@ object HologramRenderer extends TileEntitySpecialRenderer with Callable[Int] wit
     RenderState.makeItBlend()
     GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE)
 
+    val playerDistSq = x*x + y*y + z*z
+    val maxDistSq = hologram.getMaxRenderDistanceSquared
+    val fadeDistSq = hologram.getFadeStartDistanceSquared
+    RenderState.setBlendAlpha(0.75f * (if (playerDistSq > fadeDistSq) math.max(0, 1 - ((playerDistSq - fadeDistSq) / (maxDistSq - fadeDistSq)).toFloat) else 1))
+
     GL11.glPushMatrix()
     GL11.glTranslated(x + 0.5, y + 0.5, z + 0.5)
     GL11.glScaled(1.001, 1.001, 1.001) // Avoid z-fighting with other blocks.
@@ -150,7 +155,7 @@ object HologramRenderer extends TileEntitySpecialRenderer with Callable[Int] wit
           for (hz <- 0 until hologram.width) {
             for (hy <- 0 until hologram.height) {
               if (isSolid(hx, hy, hz)) {
-                val v: Int = (192 << 24) + hologram.colors(value(hx, hy, hz) - 1)
+                val v: Int = hologram.colors(value(hx, hy, hz) - 1)
                 // South
                 if (!isSolid(hx, hy, hz + 1)) {
                   tmpBuf.put(c)
@@ -252,7 +257,7 @@ object HologramRenderer extends TileEntitySpecialRenderer with Callable[Int] wit
       GL11.glInterleavedArrays(GL11.GL_T2F_V3F, 0, 0)
       GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, privateBuf)
       GL11.glEnableClientState(GL11.GL_COLOR_ARRAY)
-      GL11.glColorPointer(4, GL11.GL_UNSIGNED_BYTE, 0, 0)
+      GL11.glColorPointer(3, GL11.GL_UNSIGNED_BYTE, 4, 0)
       GL15.glBindBuffer(GL15.GL_ELEMENT_ARRAY_BUFFER, privateBuf)
 
       GL11.glDrawElements(GL11.GL_QUADS, hologram.visibleQuads * 4, GL11.GL_UNSIGNED_INT, hologram.width * hologram.width * hologram.height * 24 * 4)

src/main/scala/li/cil/oc/common/tileentity/Hologram.scala

@@ -278,6 +278,7 @@ class Hologram(var tier: Int) extends traits.Environment with SidedEnvironment w
   override def shouldRenderInPass(pass: Int) = pass == 1
 
   override def getMaxRenderDistanceSquared = scale / Settings.hologramMaxScaleByTier.max * Settings.get.hologramRenderDistance * Settings.get.hologramRenderDistance
+  def getFadeStartDistanceSquared = scale / Settings.hologramMaxScaleByTier.max * Settings.get.hologramFadeStartDistance * Settings.get.hologramFadeStartDistance
 
   override def getRenderBoundingBox = AxisAlignedBB.getAABBPool.getAABB(xCoord + 0.5 - 1.5 * scale, yCoord, zCoord - scale, xCoord + 0.5 + 1.5 * scale, yCoord + 0.25 + 2 * scale, zCoord + 0.5 + 1.5 * scale)