UV unwrapping a fire hydrant
This week we were given a model of a fire hydrant in which we needed to create the UVs for. My first step was to watch this video by FlippedNormals where they give some useful tips on creating good UVs in Maya:
Next, after opening Maya, I set the changed to the UV modelling workspace, to make switching between the UV editor and the model more efficient.
Next, I added a UV grid texture to the model, as I will be using this instead of the default Maya grid when I UV my object. To do this, I simply added a new file texture as usual, with the added step of selecting ‘Place2dTexture’ and setting the UVs to repeat 3 times:
Next I selected all the faces on the model and planar mapped the UVs onto my model. After this, I then held shift and clicked ‘Auto-seams’. This allowed me to let Maya automatically choose where the best places would be to cut the model. After this, I unfolded my UVs.
As shown in the above screenshot, unfolding the UVs resulted in the UVs all overlapping each other, so I tidied them up. This involved not only moving the overlapping UVs, but also deleting and recreating the UVs for certain areas, separating parts using the cut tool and straightening out some of my curved UVs. I straightened some of my UVs by selecting a row of edges on the UV shell I wanted to straighten and then selecting ‘straighten shell’. Next, I selected the full shell and selected ‘straighten UVs’ to finish off the process.
When making the UVs for the chain, I tried to create the UVs knowing that in industry, it is unlikely that a Texture Artist will bother painting each individual bit of the chain, which is likely to go unnoticed. Knowing this, I started to UV the chain by separating the model, this way I was able to select each individual part of the chain. After adding the UVs to one part of the chain, I then went into object mode, selected the part of the chain I had just UVd, and shift clicked the next part I wanted to texture. With these two parts selected, I then went to ‘mesh > transfer attributes’, where I set the following settings which would allow me to do this for all parts of the chain.
With the UVs for the chain created, I then needed to consider how I was going to lay them out, making them as efficient for a Texture Artist. As many parts of the chain shared the same shape and didn’t require an individual texture each, I selected all the UV shells of the chain that matched and selected ‘stack shells’. This means a Texture Artist would only need to texture 5 chain links, as opposed to however many there actually are. As there are 5 chain links in my UVs, this means there will be 5 variations of the chain so they won’t all be exactly the same texture. However, it is important to note if this were an asset in a game, it is unlikely the player would ever go close enough to need more detail than this on the chain.
Again, as the bolts on the fire hydrant were similar to the chain in the sense that they don’t need to stand out from each other, this resulted in me stacking them on top of each other as well.
When my UVs were essentially finished, I then needed to make sure the texel density of all my UVs were the same size. To do this, I selected one of my UV shells, went to the UV toolkit bar and selected the ‘Transform’ drop down option. From here, I was able to access the texel density for that specific shell by selecting ‘Get’ on texel density, giving me a number.
Knowing the texel density for this shell, I held shift and selected the rest of my UVs and clicked ‘set’, making all my UVs share the same texel density as this shell, leaving me with the following UVs:
After this, I arranged my UVs into a logical order, as in industry, my UV map would need to be understood by the Texture Artist, arranging the different parts of the chain and the bolts at the bottom, and then placing my UVs with the ones that are at the top of the fire hydrant at the top, and the UVs that are for the bottom of the hydrant at the bottom etc.
Following feedback on my UVs, I was advised not to stack the UVs for the screws in case I wanted to add specific detail to one of them. Another point was to use more of the space, as I have currently left a lot of large gaps in my UV snapshot. Finally, with the UV shell for the middle of the fire hydrant, I was advised to make it less curved.
UVs on the model: