Improve assembly line laser render (#2495)

(cherry picked from commit 2811c8e)

src/main/java/gregtech/client/particle/GTLaserBeamParticle.java

@@ -13,6 +13,7 @@
 import net.minecraft.client.renderer.texture.SimpleTexture;
 import net.minecraft.client.renderer.texture.TextureManager;
 import net.minecraft.util.ResourceLocation;
+import net.minecraft.util.math.MathHelper;
 import net.minecraft.util.math.Vec3d;
 
 import codechicken.lib.vec.Vector3;
@@ -34,11 +35,20 @@ public class GTLaserBeamParticle extends GTParticle {
     private float emit;
     private boolean doubleVertical;
 
+    private int activeTime;
+    private final int fadeInTime;
+
     public GTLaserBeamParticle(@Nullable MetaTileEntity mte, @NotNull Vector3 startPos, @NotNull Vector3 endPos) {
+        this(mte, startPos, endPos, 0);
+    }
+
+    public GTLaserBeamParticle(@Nullable MetaTileEntity mte, @NotNull Vector3 startPos, @NotNull Vector3 endPos,
+                               int fadeInTime) {
         super(startPos.x, startPos.y, startPos.z);
         this.mte = mte;
         this.direction = endPos.copy().subtract(startPos);
         this.setRenderRange(64);
+        this.fadeInTime = fadeInTime;
     }
 
     @Override
@@ -99,6 +109,15 @@ public float getAlpha() {
         return this.alpha;
     }
 
+    public float getAlpha(float partialTicks) {
+        if (this.fadeInTime > this.activeTime) {
+            return (float) (this.alpha * MathHelper.clampedLerp(
+                    (double) this.activeTime / this.fadeInTime,
+                    (double) (this.activeTime + 1) / this.fadeInTime, partialTicks));
+        }
+        return this.alpha;
+    }
+
     /**
      * Set emit speed.
      *
@@ -131,9 +150,8 @@ public void onUpdate() {
         if (mte == null || mte.isValid() &&
                 mte.getWorld().isBlockLoaded(mte.getPos(), false) &&
                 mte.getWorld().getTileEntity(mte.getPos()) == mte.getHolder()) {
-            return;
-        }
-        setExpired();
+            this.activeTime++;
+        } else setExpired();
     }
 
     @Override
@@ -169,7 +187,7 @@ public void renderParticle(@NotNull BufferBuilder buffer, @NotNull EffectRenderC
                 bodyTexture.getGlTextureId(),
                 headTexture == null ? -1 :
                         headTexture.getGlTextureId(),
-                direction, cameraDirection, beamHeight, headWidth, alpha, offset);
+                direction, cameraDirection, beamHeight, headWidth, this.getAlpha(context.partialTicks()), offset);
         GlStateManager.translate(context.cameraX() - posX, context.cameraY() - posY, context.cameraZ() - posZ);
     }
 

src/main/java/gregtech/common/metatileentities/multi/electric/MetaTileEntityAssemblyLine.java

@@ -65,6 +65,7 @@ public class MetaTileEntityAssemblyLine extends RecipeMapMultiblockController {
     @SideOnly(Side.CLIENT)
     private GTLaserBeamParticle[][] beamParticles;
     private int beamCount;
+    private int beamTime;
 
     public MetaTileEntityAssemblyLine(ResourceLocation metaTileEntityId) {
         super(metaTileEntityId, RecipeMaps.ASSEMBLY_LINE_RECIPES);
@@ -189,14 +190,22 @@ public void update() {
                 // beams and the maximum progress in the recipe.
                 int beamTime = Math.max(1, maxProgress / maxBeams);
 
-                int currentBeamCount = Math.min(maxBeams, getRecipeMapWorkable().getProgress() / beamTime);
+                int beamCount = Math.min(maxBeams, getRecipeMapWorkable().getProgress() / beamTime + 1);
 
-                if (currentBeamCount != beamCount) {
-                    beamCount = currentBeamCount;
+                if (beamCount != this.beamCount) {
+                    if (beamCount < this.beamCount) {
+                        // if beam count decreases, the last beam in the queue needs to be removed for the sake of fade
+                        // time.
+                        this.beamCount = Math.max(0, beamCount - 1);
+                        writeCustomData(GregtechDataCodes.UPDATE_PARTICLE, this::writeParticles);
+                    }
+                    this.beamTime = beamTime;
+                    this.beamCount = beamCount;
                     writeCustomData(GregtechDataCodes.UPDATE_PARTICLE, this::writeParticles);
                 }
             } else if (beamCount != 0) {
-                beamCount = 0;
+                this.beamTime = 0;
+                this.beamCount = 0;
                 writeCustomData(GregtechDataCodes.UPDATE_PARTICLE, this::writeParticles);
             }
         }
@@ -239,11 +248,13 @@ public void onRemoval() {
 
     private void writeParticles(@NotNull PacketBuffer buf) {
         buf.writeVarInt(beamCount);
+        buf.writeVarInt(beamTime);
     }
 
     @SideOnly(Side.CLIENT)
     private void readParticles(@NotNull PacketBuffer buf) {
         beamCount = buf.readVarInt();
+        beamTime = buf.readVarInt();
         if (beamParticles == null) {
             beamParticles = new GTLaserBeamParticle[17][2];
         }
@@ -306,7 +317,7 @@ private void readParticles(@NotNull PacketBuffer buf) {
     @NotNull
     @SideOnly(Side.CLIENT)
     private GTLaserBeamParticle createALParticles(Vector3 startPos, Vector3 endPos) {
-        return new GTLaserBeamParticle(this, startPos, endPos)
+        return new GTLaserBeamParticle(this, startPos, endPos, beamTime)
                 .setBody(LASER_LOCATION)
                 .setBeamHeight(0.125f)
                 // Try commenting or adjusting on the next four lines to see what happens