You are almost there with your observation...
"As best as I can tell, the projection is just from the image texture onto the object."
basically it is, the UV map is the object laid out on a flat surface.
An easy one to think off, the world is spherical, right?
But maps of the world are flat pieces of paper.
A flat UV map to be projected onto a spherical object may look something like this...
The UV map is practically everything, it's doing all the hard work of mapping the image, without it there is no texture on the object. As Martin says you're thinking about it as a real projector would work, but that is not what is happening. You can try a simple experiment and mess around with the UV's and see how things change.
The UV Map is a type of coordinate system to map out texture space. They decided to use UV instead of XY to avoid confusion for developers. So you're texture(image) has a coordinate system if ## pixels(picture elements) wide by ## pixels high. Blender starts from bottom left corner. Note: some software start at top left corner in case you're using multiple programs. The image width and height become 1 UV Map unit or 1 copy of texture space. This means means that if you switch images with different resolution the UV Map automatically adjust. This Map unit is known as a maps bounds or boundaries. If you map your mesh larger than the boundary then by default the image will be repeated. It can be set to clip which means everything outside the boundary is alpha 0. It can be extend which just uses the colors of the last row/column if pixels. Then these texels(texture elements) are applied by the mapping type, In this case color, to the mesh.
I have used different UV maps, but the result is the same. Could someone supply me with a blend file that demonstrates how the UV projector module interprets two different UV maps on the same object differently?
Consider the following: If the UV map makes a difference in how the modifier works, then two different UV maps ought produce different results in the modifier. But I have tried different UV maps, and I have seen no difference in the working of the UV Projection modifier.
Basically it's just an informative inquiry more than a question then. But yeah, there's always the Fundamentals of UV's:
https://cgcookie.com/courses/fundamentals-of-texturing-in-blender
Hi Bee,
The UV Map doesn't make a difference in how the UV Project Modifier works!
If you have no UV Map and leave the field in the Modifier blank, then Blender makes a Map for you (called Float2).
You can have more than one UV Map and then it is good to specify in the Modifier which one you want to use.
What a UV Map is...an example:
A Cube has 6 Faces and each of those Faces has 4 corners. So there you have 24 Face Corners...these are numbered (indexed).
Each Face Corner is then mapped to a certain point in the Image (U, V Coordinates) and the rest of the Image is interpolated between those points.
It is noble, but I'd recommend you don't try to understand everything...just keep going: over time, more and more things will become clear.
Basically it's just an informative inquiry more than a question then.
It's a question. Why are you being so hard-assed about this? I just want to know how the modifier that is in use here works. That seems like a completely legitimate question to me. I don't see how I have called down this rudeness upon myself from you. Please try to be more polite and not incinerate anyone with a real, honest question.
The UV Map doesn't make a difference in how the UV Project Modifier works!
OK, but that just seems really odd. Why would there even be a slot for the UV map? This still just makes no sense at all to me.
Sorry, I just now realized you're asking about the UV Map as far as the UV Project modifier. In this case the UV Map that you select is the one that will be modified by the modifier. It doesn't actual make use of the existing map's information. This just becomes the place where the mapping from the projectors(9 max if I remember correctly) are stored when you apply the modifier. So, yes changing the UV Map won't change anything other than which UV Map will get overwritten.
Thanks for the info, Dwayne. That makes much more sense now, that it's the target rather than the source of data.
Martin, thanks for the help. I now see in retrospect that you completely understood what the UV Project modifier does. I just wasn't able to get a handle on the UV map slot as a destination, rather than a source. I was hung up on the concept of the existing UV map being "projected" onto the mesh.
For that matter, perhaps the UV Projector should be called the "UV Inhaler".
