Why cant UV mapping be a one click deal

[Per-Anders]

try bodypaint sometime. it has a number of "Optimal mapping" methods. The problem is that

( a ) You get Seams

( b ) You get overlapping polygons (unless you bring your distortion level down to 0 in which case you tend to end up with just a page full of individual polygons).

( c ) Not every object is cube like, or suits cubic mapping

For what you describe you just want to use cubic mapping... you should try it sometime. You end up with polygons overlapping all over the shop on all but the simplest of models.

There are additionally a number of other automatic uving methods, mostly revolving around marching through the surrounding polygons and unfolding them... a bit like an origami in reverse. These tend to require you to make polygon or edge selections for whereyou want breaks to occur, so couldn't really be considered a "one click process" however they are considerably easier than most other methods currently available.

[OptimusDinkus]

Well, I didnt mean to imply (but it sort of looks like I did) for it to be a one click deal. I mean like skinning for instance, its a technical matter that requires tweaking, but for goodness sakes, cylindrical mapping a complex weave of characterstics for a head that sort of looks like a cylender, makes me go ape crap after spending hours tweaking the uv's. What I dont understand though is why do programs allow you to distrot and stretch the polygones? And Im just asking this not because of arrogance towards mapping, just trying to find even better ways to enhance my workflo. Ill check out body paint though.

[iSOBigD]

Well, the program "allows" you to do whatever you want for whatever the reason. Maybe some people Want a texture to be distorted.

I think the best thing to do is to try to do as many planar projections as you can. What I mean is, if you have a space ship, for example, try to find relatively flat parts of the model, give them a color, then use a planar projection...then you can obviousely edit the UVs and do whatever you want with them.

Programs simply can't do the job for you properly (yet?) unless you have very, very basic objects. You can have all the polygons placed in 2D without overlapping, but like mdme_sadie said, you'll probably have individual polygons...you can also have all kinds of mishaped parts or parts that should be large but are one pixel in the map...all these things just make it almost impossible to paint it well afterwards using a 2D program. ZBrush's projection master and Deep Paint 3D's projection mode allow you to texture models even if the map isn't too great and polygons aren't joined together at the right places, but I think it's always best to just spend hours perfecting the UV map manually so you can use photoshop or whatever program after.

[jbo]

they "allow" for distortion, because without it, you would have hundreds or thousands of seams. pretty much every two polys would have to be it's own shell unless they were already part of a flat surface. anyway, your idea is actually a fairly common workflow, though not often used on heads, because cylindrical mapping really is easier in that case. there are probably scripts in existince that help, but if not, maybe you should make one.http://cgtalk.com/images/smilies/smile.gif

[Ian Jones]

If you think about it, you will always have distortion with your mapping on complex organic shapes and curves, because polygons are simplified representations of forms even when you break every polygon apart to seperate elements as already mentioned and lay it out flat you will never be able to project a flat texture onto an infinitely detailed surface like those in real life.

There are UVW tools such as in 3dsmax like 'relax' which work upon vertices and attempt to evenly distribute them so that in effect it tries to push and pull the polygons around so that it evenly distributes distortion in problematic areas. It works upon tension between vertices.. so a vertice with a long edge on one side and a short edge coming into it on the opposite side will move towards the long edge to even out the tension and average the position of the vertice. Imagine two rubber bands connected... the connection will spring to the center which is the most relaxed and even point between the two tensions. I'm not sure what the equivalent tools in ohter programs are like, but relax seems like the sort of tool you may find useful.

[Goon]

Take a look at LSCM unwrapping. Blender has it. Wings3d has it. And there is a dedicated UV application that has it (can't remember the name tho). Houdini has pelting, which produces some fairly similar uvs, though I think the underlying principle is different. What you are talking about does exist. And it is incredibly nice to use, for some situations.

It does have issues though, because you don't have too much control over how your UV's turn out. Things like being able to pin vertices help fix that.
Also the size of uvs is not consistant throughout. So, say you are unwrapping a finger. Simply cut a seam on the side, and unwrap. However the fingernail area will likely cover less uv area than the wrest of the hand. So if you have high textural detail in that area, you have a problem.

In some situations LSCM mapping isn't entirely appropriate, or might be less appropriate than another projection method, but it does make UV mapping surfaces very easy and quick.

[Stevemeister]

because texture mapping is a complicated mathematical optimization process that doesn't guarantee you'll always get the best solution. if your mesh has 1,000 points, the uv optimization will have 2,000 variables to figure out. if you've ever tried implementing a uv-optimizing plugin from research articles, you'll see that the edge, angle, and dynamics-based flattening techniques all have complicated equations with many local minima. minimizing distortions really is a hit-or-miss technique that requires alot of tweaking.

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