Materials
I know I say I’m “putting it all together” often, but this time I promise. I just keep putting more little things together!
Today, I ported the texture and normal maps I created yesterday in ZBrush to Cinema4D. Since the fetal model is going to be just one model – with a pose morph – I wanted to set up a way to morph between the different UV maps. I ended up using a bit of XPresso to set up easy morph controllers.
The User Data sliders control both the UVs and the Pose Morph percentages, so they can controlled from one slider.
Screenshot of Cinema4D, showing everything that goes into the XPresso set-up
Material nodes
UV Nodes
I set up each UV map from each fetal stage, and attached it to a User Data float input on the origin model. All of the textures feed into a color layer, and the User Data percentage influences the mask, so the UVs can fade smoothly into each other.
I also added another User Data input to control the amount of vasculature showing – the younger the fetus, the more transparent the skin
Look how easy it is to change the parameters! I’m super thrilled by how smoothly this all worked.
Demonstrating the automation in Cinema4D
Umbilical Cord (Pt. 2)
Since I’m nearly finished with everything the fetus will need, the next challenge was the umbilical cord. Since the stomach moves SO dramatically, I wanted the umbilical cord to be paired to the naval and move with it in a nature manner. To do this, I decided to use Cinema4D’s rope dynamics to simulate the umbilical cord.
To be set up for success, I imported the umbilical cord file into my fetus file and made some much needed scale changes. Once scaled correctly, I made the spline that was to be my “rope”, or source line for the umbilical cord, have uniform point spread.
For context, this is how I built the umbilical cord.
Image 1: I made the umbilical cord out of two sweeps around an off-center pair of circles (arteries) and a larger, also off-center circle (vein).
Image 2: Since all three circles share a center axis that is not their own, this allowed me to use the “twist” function on the sweep to twist the entire cord.
Image 3: The arteries and veins were both individual sweeps.
Image 4: I put each set into a cloner to have enough real-estate for the full twisted cord.
Image 5: I put the clones into a parent, and made an instance. I referenced the instance in a Volume Builder/Mesher with a dilate and smooth on to make the umbilical cord epithelium (UCE).
Now that I had a basic cord built, I wanted to make a nice spline for the spline wrap. Rope dynamic objects work better with evenly spaced points, so I used a matrix object to smooth out and “retopologize” my spline.
Image 1: I drew a rough spline with the spline sketch tool. I only care about form and placement right now.
Image 2: I used a Matrix to evenly place cubes on the spline. I put as many cubes as points on the curve that I want.
Image 3: I then use a Tracer to connect the objects, resulting in a smoother spline with more evenly distributed points.
I baked down the spline for now, and applied a rope tag. I set up two constraints: one, a normal rope constraint on the far end. This will be attached to the placenta.
Screenshot of the XPresso set-up in C4d
Unfortunately, there’s no way to constrain to a point on another object, so I used a robe belt tag to attach the end proximal to the fetus to a small cube that I’ve hidden from view. I then used Xpresso to attach the cube to naval point on the fetus that I wanted the umbilical cord to go into.
Normal (left) vs expanded (right) naval
I did this by linking the global position of the cube to the global position of the exact point number using Point Node in XPresso. I found the point’s reference number in the Structure explorer.
Now, the umbilical cord moves with the fetal belly! This will make the umbilical cord look a lot more natural when I do the pose morph deformations in the future. I enjoy setting up scenes like this SO much; it’s so satisfying to parameterize everything, and let the program do the heavy lifting so I only have to worry about setting up the shot later.
There’s still a couple of small things I need to correct – I need to tweak the UCE, and make sure the vessels are actually going into the naval – but I LOVE the movement!
Demonstrating the umbilical rope movements.
Small Update
I didn’t like how the UCE looked, so I replaced it with a designed spline sweep – a slightly larger and smoothed combination of the sweeps that form the vasculature. I also pulled back the proximal origin point a bit. I think I need to up the iterations on the rope simulation so it moves smoothly, but I like how it looks a bit more now!
An updated verison.