Help with UV Mapping

Help with UV Mapping

Mother clucker. I have spent the last 2 hours trying to figure out how to slap a label on a cylinder and am at my wits end. I am frazzled—and my nerves are shot. I need the most basic tutorial on applying a label to a cylinder and can't find it anywhere. The label is a .png with alpha.

1- I've messed with the UV Mapper and still can't position the label on there right.

2- When I render it, it is positioned differently than what I see in the editor.

3- Although the png has a transparent background, when I render, the background is black (not the background material).

Thanks for any help.
 
Mother clucker. I have spent the last 2 hours trying to figure out how to slap a label on a cylinder and am at my wits end. I am frazzled—and my nerves are shot. I need the most basic tutorial on applying a label to a cylinder and can't find it anywhere. The label is a .png with alpha.

1- I've messed with the UV Mapper and still can't position the label on there right.

2- When I render it, it is positioned differently than what I see in the editor.

3- Although the png has a transparent background, when I render, the background is black (not the background material).

Thanks for any help.


Try this: http://www.cheetah3d.de/forum/showthread.php?t=4115
 
More help Please ;)

Thanks for the pointer. It was helpful. What I'm trying to do is put a printed logo on top of a cylinder. The logo image I'm putting on the cylinder is a PNG with Alpha transparency. When I don't click "Use Alpha Channel" it renders the transparent part black (as expected) but when I click to "use Alpha Channel", it now makes the cylinder see through when I'm trying to see the background texture where it is transparent.

How would I do this? I am a beginner so please use easy instructions.

Thanks very much.
 
To get your image to utilize the transparency:

1. Under Add Material, use material.
2. Under color in the properties area of that material, load your png
If you're finding this still isn't working, go to Step 3. Otherwise you're done.
3. Under transparency in the properties area, check "use alpha channel"

You can also simply put it on a curved plane and "wrap" it around the circular part. Probably the easiest way to do this and match it up to your cylinder is to grab a group of polygons on your cylinder and do a Split (See Tools > Polygon > Split). Then you'll see an exact duplicate of those polygons in your object browser. Move them slightly out from the cylinder and drop your texture on the split object. It should wrap very well.

Please see images for sample effectiveness.
 

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One more time

Here is my model:
3d1.png


Here is what I'm getting when I render. Notice that where I place the logo stamp, it turns the background transparent.
3d2.png


What I'm trying to do is overlay a logo stamp over the cylinder's blue material.

Also: Notice the light blue rectangles that show up on the top and bottom of the logo. I'm not understanding where those are coming from.

Thanks again for the help.
 
In almost every 3D app, there can only be one material ball assignment per poly face. It's probably a limitation in openGL. When you assign your transparent material to those faces, you are replacing the blue material with the transparent material, so what you are seeing is perfectly normal. You cannot stack multiple materials onto a single face selection. That would be cool, but even very expensive packages like maya don't allow this. You really should make a poly decal overlay by selecting those faces and performing the "split" command. That will build you a new *.split mesh, and you can then assign your logo material to that mesh. You do not need to offset the decal mesh, it will render correctly. It might possible to build a decal shader in the upcoming v.5 of C3D that uses UV set 2 for stamps like this, but we will have to wait and see....
 
Here is my model:
3d1.png


Here is what I'm getting when I render. Notice that where I place the logo stamp, it turns the background transparent.
3d2.png


What I'm trying to do is overlay a logo stamp over the cylinder's blue material.

Also: Notice the light blue rectangles that show up on the top and bottom of the logo. I'm not understanding where those are coming from.

Thanks again for the help.

Hey m8. It might help me to understand what you're doing better if I could see the image you're trying to place. I do see in your material set that the letters are showing up transparent. Seeing your image will help me figure out what's not working.
 
Also: Notice the light blue rectangles that show up on the top and bottom of the logo. I'm not understanding where those are coming from.

Thanks again for the help.

I went to a similar problem in one of my test a while ago... as far as i remember a render tag applied to the alpha-textured object (cast shadows, receive radiosity and receive caustics off) did the trick. maybe also choosing raytrace+transparency shadow type in the light properties can help.

Cheers,
Alessandro

BTW alvordr is right about seeing the picture you want to use...
 
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@ bbelement.
Can´t you just simply fill the transparent areas of your decal with the color of the stick and map it to the desired polygons?

Cheers
Frank
 
@ bbelement.
Can´t you just simply fill the transparent areas of your decal with the color of the stick and map it to the desired polygons?

Exactly. Or in fact map all the rest of the stick onto a tiny piece of the texture with the background color on it.

@nervouschimp
Multitexturing and Decals are both supported in OpenGL btw, and in any event C3D doesn't rely on OpenGL for rendering. I believe C3D is planned to support multtexturing eventually (which is why order is important in material assignment to subselections of meshes).
 
Multitexturing and Decals are both supported in OpenGL btw said:
Um, C3D has multitexturing now. Multitexturing is the use of more than one texture at a time on a polygon to do things like bump mapping and light mapping. This is done within one complex material ATM.

Multiple material assignments per poly is different.

That's great if Cheetah is going to let you stack multiple materials per poly, most apps don't allow this. Fantastic!
 
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