This was a sculpt that I just finished for a client about a couple weeks back. Allosaurus is a favorite among a lot of dinosaur fans, and I'm no exception. Not sure why exactly people love the species so much, maybe because it's been known for so long, or maybe because it's this sleek, Jurassic predator. Whatever the reason, he was an absolute blast to sculpt.
Unlike some of my previous models, I actually started this one not from a dynamesh ball. Instead, I loaded up my T. rex model I sculpted late last year and used that as my start point.
Compared to an Allosaurus, there are some severe morphological differences to a Tyrannosaurus rex. Head size, neck length, finger count, overall proportions...but it IS a therapod, which means the basic structure is there and it just needs to be modified.
Once the general shape was blocked in, it was a matter of carving, adding, and carving the shape some more, slowly bringing it closer to the final dimensions of an Allosaurus. At this point I'm looking at a lot of reference of the skeleton, as well as some sculpts by other artists to see how they solved certain problems. Doing this with the right artists is incredibly beneficial, since it also helps me learn how they sculpt certain features and effects.
Right, so as stuff comes together and I find that my passes are becoming more focused on smaller areas and refining more minute things rather than general forms, I move towards detailing. If you don't have a solid foundation all the detail in the world will not save a good sculpture, but if your sculpt is good and your forms are true then that extra pass of finishing will really bring it to the next level.
There's three stages of detailing through with dinosaurs, and at this point it's gotten pretty methodical for myself: wrinkling, scale work, detail scale work.
First thing I do is tackle wrinkles and skin folds, which is just another level of adding minor forms and the start of the first detailing pass. I try to think about where areas on the body would develop skin folds, look at reference of birds and lizards, and emulate. These major wrinkles will show up underneath all the rest of the detail, so it's important to be as careful with these as you were with earlier forms.
After that, comes the first pass of detailing (or adding noise, I sometimes look at it.) I take a brush that resembles a rake brush (using an alpha that's supplied with Zbrush) and start to rake across the forms, almost like I'm making a cross contour drawing. I'll typically also hatch it the other direction as well just to break it up in some areas and make some more texture. Use this to emphasize rhythm lines and areas where forms flow from one to another.
|This photo shows the head a bit further along than I'm describing - I've already|
put in the hand tooled scale work ontop of my generic stamping, but you can get
a good idea of what it looks like from this.
Once I've made a pass with a generic scale detail on the body, I'll go in and add some hand tooled scales and scutes. This is done with the same tools I used for carving and adding the base forms earlier, the clay buildup brush, clay tubes brush, and masking. Certain areas that I want scutes on I'll mask then either build up a bit, pull out, or inflate to create the raised armored bump. Detail scales like the ones around the face will be tooled in by hand using the clay tubes brush. Like the rest of the stages, refer to reference and let nature inform your decision making.
When I hit the detailing stage I pretty much can switch my brain off - rarely if ever does that sort of stuff drastically alter the silhouette, so you can kinda go crazy and have fun during this part to really make it pop. Extra details like the teeth and spines on the neck area added as sub tools in Zbrush since it's easier to just insert them as separate geometry rather than pull it from the existing model.
Although it wasn't required by the client for the scope of the job (I was sculpting with the intent for the model to be available on Shapeways for the client,) I ended up painting it for fun because it would be a good challenge for me. Like surface detailing, I pretty much shut off my brain and had fun with it. Initially I had no reference for it, but once I started on a certain scheme I liked I started to look at reference of turkeys and pheasants to get some ideas.