Patch-Mesh 101
Common Questions
 

Why do patch meshes cause my frame rates to increase so much?

Simple patch meshes give you the most control over curves...
A 3x3 patch mesh is 3 rows and 3 columns of control points - if you leave them arranged as they start, that patch will appear as 2 triangles in q3, even though it has 6x6 rows and columns when drawn in q3r.

When you manipulate the control points on a simple patch mesh, the relationship between the points within any one row or column defines a (quadratic) bezier curve. Up to 6 different bezier curves can be used to make up a single patch, and the simpler these curves are, the fewer triangles the final patch will make.

If you preserve each of the rows (or columns) in a straight line while bending the patch (moving only the columns of a bevel for example), it will produce a lot fewer triangles in Q3A because it only needs to be curved in one direction.

You can use simple patch meshes and bevels cheaply and effectively, as substitutes for square-cylinder archways and complex bi-directional curves which use significantly more triangles.

Why don't the two meshes line up in the game? They look fine in Q3R and all the control points line up.

This is a problem inherent with bezier patches. It's not possible to fix it comfortably in the code, so it has to be worked around.
Every single curve patch starts off as a 3x3 square grid of points. You can bend and stretch the grid in any way you want to. A patch grid seen in q3 is made up of a number of rows and columns.

The number of rows and columns of points you see in Q3Radiant does not affect the number of rows and columns Quake3 displays the patch with. The number of rows and columns displayed is decided when the map loads - Quake3 works out how curved all the rows of points are, then picks the MOST curved row, and subdivides the patch according to how curved that row is.

Because each patch is a square grid, it cannot have more columns at the top than there are at the bottom. This means that the bottom side will be subdivided the same amount as the top side, and the left side the same as the right hand side.

This causes problems for patches the opposite sides of which are not of equal length, such as concentric curved trims. The outside edge (the longest) is used to decide how the curve is subdivided, and so the inside edge (the shortest) doesn't match up with adjacent patches which are subdivided differently.

The solution is to only use patches that have opposite edges of roughly similar length. Most of the time you can get away with small differences in length because the difference isn't big enough to change the tesselation level.

Why can't I get the texture to look right on my complex curved meshes?
Using ctrl+shift+n works by projecting the texture onto the patch from ONE of the principal planes planes (the three principal planes are the view planes you see in the 2d view). If the patch does not look flat in one of the three view planes (like a bevel or a cylinder) then projecting the texture onto it from a flat plane will not look right. For texturing square patches you can also use SET, and enter the number of times you want the texture to repeat horizontally and vertically. If you're texturing a 'capped' bevel, use TAB to select the 'cap' patch before using ctrl+shift+n.

Why do I get sparkles on the edges of my meshes and fog, water, and lava cause it too it seems?
To avoid sparkles next to your meshes make the brushes the same size as the mesh. Check out this little tutorial on that problem here. As for liquids aka (fog, water, lava), they break up the meshes and brushes at the surface so there is only one way to fix it, use a separate mesh below the surface and have the top mesh join it at the surface. The split mesh will match up with the adjacent brushes thus eliminating the sparkles.

I will add more questions and answers as I see fit got a question email me Bill Brooks

Short cut keys that will come in handy while working with meshes :

ctrl-G               Snap to grid (I use this one allot)
ctrl- I                Invert texture
shift-control-N   Cycles cap textures patch
V key              Turns on vertices so you can drag them.
control-N          Naturalize patch texture
Control-P         Toggle show patches 
shift-C             Cap selected curve
shift-S             Patch Inspector (I use this one allot)