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View Full Version : UV Mapping a Simple Box-type object, how hard can it be??



adrian
08-19-2014, 03:56 AM
Ok so this is driving me mad. I have a box-type subpatch object that I want to UV map. If you look at the screenshot you can see it's a very simple object with the underside a separate surface and hidden for the UV mapping process (ie so the object is not fully enclosed).

When using PLG_Make_UV (or PLG_Make_UV_Edit) I end up with the mesh shown in the white square, which is distorted and as such, distorts my textures.

So far I have tried the following:

* Added extra geometry so it's a tighter mesh (hence the "needless" extra geo in the mesh)
* Divided the mesh you see in the screenshot two more times so it's very dense - no difference in the UV map shape
* Used PLG_Make_UV_Edit to manually select a seam point
* Using the PLG_Relax_UV tools to no effect
* Tried using ALL of the different options within the PLG tools
* Selecting various sides of the object and removing them, results vary from bad to awful
* Used the inbuilt ABF Unwrap tool with the same result as shown in the screenshot


In addition I have also tried manually moving the points in the UV Texture so the four sides of the mesh are square in the UV map; however the texture still ends up distorted and rubbish as if I hadn't even moved any points at all.

Seriously how difficult can UV-mapping a simple object like this be? All I need to do is select "cubic" in surface editor, apply a texture and voila! A perfectly mapped texture with no distortion - which is great except of course I have zero control over the texture this way.

Please tell me I'm missing something simple.

123734

Dodgy
08-19-2014, 05:35 AM
Well it's obviously going to be distorted, it's trying to flatten your 3d shape into a flat plane. For a shape like that if you don't want distortion you should be using the standard projection UV mapping, or perhaps making seams along the corners of the object. Basically imagine the shape exists, and you want to flatten it out, you'd have to cut it with scissors along the edges, and then flatten it. Even then it'd probably be a bit distorted.

MarcusM
08-19-2014, 07:35 AM
Upload this object.

erikals
08-19-2014, 08:17 AM
what Dodgy says,

you could use this trick > https://www.youtube.com/watch?v=Zo8EnJUi3Ew

and end up with this (see attachment)

flat sides will map fine, but angled sides will need a bit tweaking (stretching in this case)
this will have to be done manually with the stretch tool... (or for example plg Relax UV)

erikals
08-19-2014, 08:52 AM
remember to use "Select By Normal" by the way to save time...

https://www.youtube.com/watch?v=NmYdutZVJKc

JoePoe
08-19-2014, 10:58 AM
I think the OP is referring to the curved edges of the UVed geometry. I would like to know why that's happening too. Can't reproduce it (standard LW UVing here not PLG).

Edit: The texture stretching, of course, is the other issue here and should be addressed as everyone has said. It's going to happen even with straight edges in the UV with that type of unseamed/unfolded/or not ungrouped projection in the UV..

adrian
08-19-2014, 12:40 PM
Thanks for the replies and YouTube links which I will check out. In the meantime I have managed to set the UVs by doing each side individually. Of course this isn't ideal either as there are horrible seams where each texture meets but hopefully in this instance I will be able to hide them.

Yes as JoePoe pointed out, it's the curved edges (that are straight on the mesh) which is what I want to get rid of.

MSherak
08-19-2014, 02:39 PM
Ok so this is driving me mad. I have a box-type subpatch object that I want to UV map. If you look at the screenshot you can see it's a very simple object with the underside a separate surface and hidden for the UV mapping process (ie so the object is not fully enclosed).

When using PLG_Make_UV (or PLG_Make_UV_Edit) I end up with the mesh shown in the white square, which is distorted and as such, distorts my textures.

So far I have tried the following:

* Added extra geometry so it's a tighter mesh (hence the "needless" extra geo in the mesh)
* Divided the mesh you see in the screenshot two more times so it's very dense - no difference in the UV map shape
* Used PLG_Make_UV_Edit to manually select a seam point
* Using the PLG_Relax_UV tools to no effect
* Tried using ALL of the different options within the PLG tools
* Selecting various sides of the object and removing them, results vary from bad to awful
* Used the inbuilt ABF Unwrap tool with the same result as shown in the screenshot


In addition I have also tried manually moving the points in the UV Texture so the four sides of the mesh are square in the UV map; however the texture still ends up distorted and rubbish as if I hadn't even moved any points at all.

Seriously how difficult can UV-mapping a simple object like this be? All I need to do is select "cubic" in surface editor, apply a texture and voila! A perfectly mapped texture with no distortion - which is great except of course I have zero control over the texture this way.

Please tell me I'm missing something simple.

123734

The distortion one is seeing here is correct for the math for both PLG and ABF, they try to keep the texel ratios in check based on the edge selections (In this case none). Never assume a model, no matter the look, is easy to UV. As you mention it's a box-type. Nope. It's a box or it's not. This case the box it started out as, is now a not, and now a complex object from a math point of view. To the Human eye, YES, it looks like a box-ish shape, the simplicity of the human eye and brain. To the computer these are just numbers and has no idea what shape it is, nor does is care. 3D to 2D space is all about volume area not alignments. Alignment is what a human wants, mathematically these results one sees is correct for the amount of input that the tool has received. Now if one wants all this to be in strait lines in UV space and texel correct to 3D space then one must give the tool some guides to follow. In this case edges (Seams). With these selections in place it is easier for the tool to do the alignment. Now most of the time we just select one edge and expect it to all work. Like anything the more guidance the better the results.

I have attached a model and some images of different UV types of projections. Just load an image (tile) and place it on the surface. Then just switch between UV's to see the results. Hopefully by seeing the different area volumes being defined it might start to kick in other ways of thinking to unwrap this model. PLG is still in my opinion the best UV unwrapper's out there, and it just happens to be a plugin that works within LW.

PS. to do a Cubic UV just like in the surface editor, do three manual projections to the normals facing along each axis based. use the center position and size from the cubic map in the surface editor.

adrian
08-20-2014, 02:28 AM
Thanks so much for a detailed and informative post. I feel a bit guilty now for expecting it all to be so easy but having read the above post it's changed my mindset a bit. Thanks for the model too which I will play around with. I will never again assume it should be easy to UV map something.

erikals
08-20-2014, 02:35 AM
Sherak, yes thank you http://erikalstad.com/backup/misc.php_files/047.gif very nice explanation http://erikalstad.com/backup/misc.php_files/035.gif



http://forums.newtek.com/images/misc/quote_icon.pngAdrian
I will never again assume it should be easy to UV map something.

if you UV map a lot, you might want to check out 3DCoat or the better, UVLayout
http://forums.newtek.com/showthread.php?143064-Which-is-the-best-UV-Map-software