Tutorial: Using the Clipper Tool (large images)

Post by **obsidian** » Wed Jun 13, 2007 12:36 am

This tutorial covers how to use GtkRadiant's clipper tool for 2-point, 3-point and the little known patch-clipping methods. This tutorial was created using GtkRadiant 1.4.0 and while there are some small differences in 1.5.0 or other versions, they should all work relatively the same way.

2-Point Clipping:

3-Point Clipping:

Using a Patch as a Clipping Plane:

Post by **Survivor** » Wed Jun 13, 2007 7:33 am

Obsidian, tremulous has a mapping wiki going on here. Do you mind if I add this to it?

Post by **wattro** » Wed Jun 13, 2007 9:11 am

i didn't know you could clip with a patch =)

awesome!

Post by **corsair** » Wed Jun 13, 2007 11:46 am

heh, you can't clip a patch =)
obsidian just clipped the brush behind the patch, giving a face that's more or less the same as the patch's (which is only used as reference for his 3 clipping points, and it could be used as a solid to block vis / create portals, since patches dont do that)

Post by **pjw** » Wed Jun 13, 2007 1:28 pm

corsair wrote:heh, you can't clip a patch =)

wattro didn't say you could. He said clip with a patch, which is what obsidian showed.

corsair wrote:it could be used as a solid to block vis / create portals, since patches dont do that)

I think you mean "could not".

I was also unaware of this feature. Very cool.

Post by **Kaz** » Wed Jun 13, 2007 1:37 pm

omg you can clip with patches?!? Where have I been!!?

Post by **obsidian** » Wed Jun 13, 2007 3:11 pm

Survivor wrote:Obsidian, tremulous has a mapping wiki going on here. Do you mind if I add this to it?

Be my guest. Good to have a wiki.

You can all thank ydnar for patch clipping. I guess he was bored one day and started poking around with the GtkRadiant source. He compiled a custom patch-clip exe and released it. It was eventually merged into the 1.4.0 branch.

Patch clipping does not work in 1.5.0.
Patch clipping takes three vertex corners of the patch and uses them to form the clipping plane.

Post by **dnky** » Wed Jun 13, 2007 3:51 pm

*cough* I didnt know you could clip with a patch either

Post by **Silicone_Milk** » Wed Jun 13, 2007 5:54 pm

Patch-Clipping : GTKRadiant 1.4.0's best kept secret.
Until now.

Post by **pjw** » Wed Jun 13, 2007 6:13 pm

obsidian wrote:Patch clipping takes three vertex corners of the patch and uses them to form the clipping plane.

As sock pointed out to me this morning, that could easily be potentially ugly, if you're not very careful. There's nothing that says that those three corner verts will actually form a cutting plane that's on grid with the edges of the brush you're trying to cut.

In other words, it would be like using the clipper, but not worrying about whether the points were actually on the brush edges, and just tossing them out into space. Yay for verts off the grid.

After thinking it through a bit, I'm sure I'll just stick with the clipper--it's much easier to avoid ugliness by just putting your clipping points on the brush edges/faces than by trying to make sure that the intersecting patch is placed properly.

My $0.02.

Edit:

corsair wrote:Though, it could bit unsafe to go ahead an do clipping with patches -- it might give some verts that are off the grid when being careless.

LOL. We posted at the same time. Get out of my head!!

Post by **corsair** » Wed Jun 13, 2007 6:13 pm

I hate when I read things that aren't there, but damnit, thats neat obsidian!

pjw: I actualy didn't mean that, but you're right the way you read it... I meant that the resulting brush could serve as a visblocker for the patch that was used, guess I wrote a bad sentence there.
sry for that, I blame some odd nights =)

edit: Hey! lol.. I already edited it out for you.. u!

Post by **obsidian** » Wed Jun 13, 2007 6:21 pm

@pjw: The reason for patch-clipping is just so that you can visualize the clip points, which is not always the easiest thing to do, especially with 3 points. With either patch-clipping or normal point clipping, when used unwisely can always result in vertex points off grid.

I guess I didn't show that clearly in the pics above, I should have kept the patch corners flush with the brush, but that would have been hard to see in the screenshots, so I actually extended them outwards a bit so you can see the whole patch.

Anyway, it's an alternative method of clipping that might be useful in some tricky situations where it is difficult to place the clip points. Personally, I haven't found much use for it either, but good to know it's there.

Post by **Kat** » Wed Jun 13, 2007 8:06 pm

pjw wrote:...suff...

You wouldn't want to be using it for archtectural stuff unless you took the time to align the verts properly - mind you, you could always collapse the patch into a single 'tris' to get a proper *3 point* clipping plain; if a patch has 4 points which *3* does the feature choose from?.

For making organic stuff it'd be a great way to visualise the 'sculpt' of a cut where vert alignment isn't that much of an issue.

Post by **pjw** » Wed Jun 13, 2007 9:04 pm

Kat wrote:if a patch has 4 points which *3* does the feature choose from?

Doesn't matter. Any three points on a (flat) plane always define the same plane.

Just for fun, I played around for a couple of minutes clipping with a curved patch. It was tough to predict, at times, at what angle the clipping plane was going to appear...