I’ve spent the last few weeks learning how to unwrap UV maps for a 3D model, so that any texturing and painting rusults in Photoshop CC are more controllable. For exmple, take this primative object that I created in Cinema 4D, and objened into Photoshop as an OBJ file.
Within Photoshop the standard brush tool can be used to paint directly onto the 3D geometry and project the paint marks onto the texture map.
Painting on one face of this particular object will result in the paint appearing on every side. This can be quite confusing to why it happens. If the material for cube is opened, it’s fairly obvious why.
To access the materials for a 3D Object in Photoshop, click on the material object in the 3D menu (marked yellow) and select to open/edit the Diffuse texture (marked in red) from the folder (marked in purple)
It turns out that we only see one face, the reason that we see this result on all faces is that each of the other faces takes the texture from a single definition.
3D Texture maps are controled by something called UV’s or UVW (in some cases). A UV is a collection of reference points that link texture back to the original Polygons. The U and V are simply references for an X and Y coordinates reference, but are represented in a 2D fashion, this is called un-wrapped geometry. These 2D representations will make texturing and painting much simpler and more controllable. In the case of the cube there are six faces, so therefore six UV’s exist. however, the UV’s in this example are all positioned in the same place, that’s why we only see one, but in reality there are six overlapping.
This might be want you need to paint the cube for your texture, but if you need to have differnt designs, patterns and textures on each face, then this won’t work for you and will need to be corrected.
Photoshop CC can read the UV’s that have been created from a 3D Package and also has a way to automaticaly correct the UV’s by choosing ‘Generate UVs’ from the 3D Menu. This again, might be ok for the texture that you would like to paint. However, if you would like to get full control of the UV’s, then you will need to unwrap them using a dedicated 3D package.
I’m no expert in UV unwrapping and it’s a bit of a dark art, and as my experience grows i’ll write more content, so this is just an intro to get you started. When I was looking into this topic, I found it difficult to get a consistent method of unwrapping UV’s. But I did find one resource that helped me understand the unwrapping process, you can find it here (Lester Banks). As there are many different 3D packages out there, it’s hard to cover them all. So my preference is Cinema 4D and that is what’s explained here. N.B. You will need Cinema 4D Body Paint to do UV unwrapping with your models.
Within Cinema, you can see the same object that existed in Photoshop CC above. N.B. This is a very simple tutorial and not the only way to perform the unwrapping.
When you unwrap, you will want to think about how the texures will be laid on on the final object.
The first thing inside Cinema is to make the object editbale, Clickin the ‘Make Editable’ button in cinema to do this (marked in red below)
N.B. Make Editable essentially converts the object from parametric (you can still change parameters) to polygons. This is typically done when want to edit the points/polygons by hand, edit the UVW map, etc.
The next step is to define the points that will be used to refer the object on the UVW map. For the cube, move the Cinema view port into top mode.
Each window has a window selector in the top right (as shown in red below). When on the perspective mode as in above, clicking this button (marked in red below), will take you into multi view mode, then clicking on the same button on the required view will show it in full screen.
Move Cinema into the Points view (by clicking on the points mode (marked in red).
On the top view, hold the SHIFT key down and click on each corner of the square.
N.B. Points refer to Vertices. Vertices/Points are the collections that hold the polygons/edges of the model together.
Now move back to perspective mode in the viewport.
The 2D representation of the 3D model (or the UV’s) is a flattened version, so obviously when converting a 3D object to a 2D representation it will need to be cut in certain places. By selecting the edge tool (marked in red), will tell Cinema how to cut the model and lay it down on a 2D surface (Similar to when a tailor makes a suit). In the case below, each vertical edge of the cube is selected (using the SHIFT key), Cinema will cut the model on each edge.
To unwrap this model as a conventional represention, we need to specify the bottom and how that will be cut, bearning in mind how it will be unfolded. We will just specify three sides to cut, leaving the 4th connected to the uncut faces. (holding the SHIFT key will ensure that these are selected as a collection, if the wrong edge is selected, then pressing CMD/CTRL will allow you to remove a single edge from the collection).
Now, we can unwrap the model into the 2D UV.
The object marked in Red shows that the model has a UV map assigned to it. To access this, change the view port to be in BP UV Edit. When inside the BP UV Edit, you can select ‘UV Mesh / Show UV Mesh’, and in this case, the lines shown in the yellow box below, will be the same as what Photoshop is showing.
Move Cinema into the top view, as we are now going to specify on the UV where the selected points are. To start specfiying the UV, click the UV property (marked in red), then move the viewport into UV mode (marked in yellow). As long as a UV property exists the area marked in purple will become active).
There are many variataions to the next step, but for this we are specifying the points, so just click the Projection / Frontal. This will take the points and represent them on the UV (show below).
Move cinema into perspective view and click the Relax UV tab.
Make sure the ‘Pin Point selection’ is turned on (but the use tag is turned off), as we will use the active selection, not a saved selection. And make sure that ‘Cut Selected Edges’ is turned on (but the use tag is turned off), for the same reason as just mentioned. Also, make sure that LSCM is selected, as well as having Auto re-align turned on.
Then click on Apply!
Hopefully the 2D UV will be shown on the right hand side, which will have collapse all six surfaces
Save the Object and export as either Collada 1.4 or OBJ from Cinema 4D, then open into Photoshop CC. Now painting on the 3D model or on the 2D UV map by using the standard Photoshop CC brush tool, should be much easier and each side can be painted independently.
Hopefully this post will get you started into creating and unwraping UV’s, as well as painting on 2D UV’s and 3D objects within Photoshop CC.
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