Visibility Control in Hammer
Method 1 --- Hiding/Unhiding
In this picture, the big orange tubes (they are func_dustmotes) take up alot of space, and could get pretty annoying to map around. One thing we can do is hide them, so select them all, and hit the Hide Selected button (). You should now see something like this:
Enter a name for the things you are hiding (the name will be 'dustmotes' in this case), then click OK. The things you had selected should have suddenly dissapeared. To the right of the screen there is a box labelled "VisGroups:"
A new entry has been created, named "dustmotes", with a little empty box next to it. Ticking this box will make everything in the group visible again, and unticking it will hide them again. To delete a VisGroup, simply click and drag it into one of the viewports. This will not actually delete any of the entities in the group, just remove the group from the list and unhide any entities that were in it.
Method 2 --- Cordon Bounds
This Counter-Terrorist spawn looks pretty bare. I'd like to put some more stuff in it, but all the things Hammer is rendering is making it lag pretty badly. We could always select everything else and hide it, but that would make a new visgroup, etc. A more temporary solution is to set Cordon Bounds around the stuff we want to be rendered.
In the top toolbar you will see these buttons:
Click the one i have embossed. A red box will pop up on the viewports, with handles on it to resize it (very similar to the box that pops up when you create primitives such as boxes). Drag this box around the CT Spawn, the bit we want to be rendered. You should see something like this:
There is a button next to the 'Edit Cordon Bounds' button. It similar, but it is a solid box with the black and yellow stripes on it. Hover over this button and it will say 'Toggle Cordon State':
Youll notice that all you've done so far has had no effect. This is because you have to click this second button, so click it and you should see something like this:
Everything who's center is not inside the big red box will not get rendered in Hammer, leaving you a nice clean little space to map with. To bring back the rest of your map, just click on the 'Toggle Cordon State' button again.