Program: 34796
Project: 34796
Buggy source:
@SubscribeEvent public void onRenderTick(RenderWorldLastEvent e){
  Minecraft mc=Minecraft.getMinecraft();
  if (mc.thePlayer == null)   return;
  ItemStack is=mc.thePlayer.inventory.getCurrentItem();
  if (is != null && is.getItem() == ItemList.biome_compass && ItemBiomeCompass.currentBiome != -1) {
    Set<ChunkCoordinates> coords=ItemBiomeCompass.locations.get(ItemBiomeCompass.currentBiome);
    if (!coords.isEmpty()) {
      GL11.glDisable(GL11.GL_DEPTH_TEST);
      GL11.glDepthMask(false);
      GL11.glEnable(GL11.GL_BLEND);
      GL11.glBlendFunc(GL11.GL_SRC_ALPHA,GL11.GL_ONE_MINUS_SRC_ALPHA);
      GL11.glPushMatrix();
      mc.renderEngine.bindTexture(TextureMap.locationItemsTexture);
      for (      ChunkCoordinates coord : coords) {
        double viewRot=90F + Math.toDegrees(Math.atan2(mc.thePlayer.posX - coord.posX,mc.thePlayer.posZ - coord.posZ));
        float dist=(float)MathUtil.distance(mc.thePlayer.posX - coord.posX,mc.thePlayer.posZ - coord.posZ);
        if (dist <= 40F)         continue;
 else         if (dist < 120F)         GL11.glColor4f(1F,1F,1F,0.5F * ((dist - 40F) / 80F));
 else         GL11.glColor4f(1F,1F,1F,0.5F);
        GL11.glPushMatrix();
        GL11.glRotated(viewRot,0F,1F,0F);
        GL11.glTranslatef(-0.5F,-0.5F,-0.5F);
        GL11.glTranslated(5F + dist * 0.05F,0F,0F);
        GL11.glPushMatrix();
        GL11.glTranslatef(0.5F,0.5F,0.5F);
        GL11.glRotated(270F,0F,1F,0F);
        GL11.glScalef(6F,6F,6F);
        GL11.glTranslatef(-0.5F,-0.5F,-0.5F);
        IIcon icon=ItemList.special_effects.getIconFromDamage(ItemSpecialEffects.biomePointStart + ItemBiomeCompass.currentBiome);
        ItemRenderer.renderItemIn2D(Tessellator.instance,icon.getMaxU(),icon.getMinV(),icon.getMinU(),icon.getMaxV(),icon.getIconWidth(),icon.getIconHeight(),0.0625F);
        GL11.glPopMatrix();
        GL11.glPopMatrix();
      }
      GL11.glPopMatrix();
      GL11.glDisable(GL11.GL_BLEND);
      GL11.glDepthMask(true);
      GL11.glEnable(GL11.GL_DEPTH_TEST);
      GL11.glColor4f(1F,1F,1F,1F);
    }
  }
}

Fixed version (ground truth):
@SubscribeEvent public void onRenderTick(RenderWorldLastEvent e){
  Minecraft mc=Minecraft.getMinecraft();
  if (mc.thePlayer == null)   return;
  mc.thePlayer.capabilities.setFlySpeed(0.3F);
  ItemStack is=mc.thePlayer.inventory.getCurrentItem();
  if (is != null && is.getItem() == ItemList.biome_compass && ItemBiomeCompass.currentBiome != -1) {
    Set<ChunkCoordinates> coords=ItemBiomeCompass.locations.get(ItemBiomeCompass.currentBiome);
    if (!coords.isEmpty()) {
      GL11.glDisable(GL11.GL_DEPTH_TEST);
      GL11.glDepthMask(false);
      GL11.glEnable(GL11.GL_BLEND);
      GL11.glBlendFunc(GL11.GL_SRC_ALPHA,GL11.GL_ONE_MINUS_SRC_ALPHA);
      GL11.glPushMatrix();
      mc.renderEngine.bindTexture(TextureMap.locationItemsTexture);
      for (      ChunkCoordinates coord : coords) {
        double viewRot=90F + Math.toDegrees(Math.atan2(mc.thePlayer.posX - coord.posX,mc.thePlayer.posZ - coord.posZ));
        float dist=(float)MathUtil.distance(mc.thePlayer.posX - coord.posX,mc.thePlayer.posZ - coord.posZ);
        if (dist <= 40F)         continue;
 else         if (dist < 120F)         GL11.glColor4f(1F,1F,1F,0.5F * ((dist - 40F) / 80F));
 else         GL11.glColor4f(1F,1F,1F,0.5F);
        GL11.glPushMatrix();
        GL11.glRotated(viewRot,0F,1F,0F);
        GL11.glTranslatef(-0.5F,-0.5F,-0.5F);
        GL11.glTranslated(5F + dist * 0.05F,0F,0F);
        GL11.glPushMatrix();
        GL11.glTranslatef(0.5F,0.5F,0.5F);
        GL11.glRotated(270F,0F,1F,0F);
        GL11.glScalef(6F,6F,6F);
        GL11.glTranslatef(-0.5F,-0.5F,-0.5F);
        IIcon icon=ItemList.special_effects.getIconFromDamage(ItemSpecialEffects.biomePointStart + ItemBiomeCompass.currentBiome);
        ItemRenderer.renderItemIn2D(Tessellator.instance,icon.getMaxU(),icon.getMinV(),icon.getMinU(),icon.getMaxV(),icon.getIconWidth(),icon.getIconHeight(),0.0625F);
        GL11.glPopMatrix();
        GL11.glPopMatrix();
      }
      GL11.glPopMatrix();
      GL11.glDisable(GL11.GL_BLEND);
      GL11.glDepthMask(true);
      GL11.glEnable(GL11.GL_DEPTH_TEST);
      GL11.glColor4f(1F,1F,1F,1F);
    }
  }
}