Amniotic Fluid
As I move onto animating Scene 2, I have to figure out how I want to handle the amniotic fluid. I decided to do this procedurally – again – so that when the fetus moves, the fluid “ripples” around it.
Volume builder set-up
Thankfully, C4D is full of tools to make this easy! I isolated out the inside polygons of the uterus to use as my base. I put these, as well as an instance of the fetus, umbilical cord, and placenta into a Volume Builder, and set them to subtract. I later removed the umbilical cord from this set, because it was causing problems, but this set me up well.
Result of the volume builder.
To give it some more life, I put a displacement deformer on top of the volume mesher, and played with a couple different noise animations.
Different iterations of the displacement on the fluid.
Screenshot of the fluid without the uterus.
Screenshot of the fluid within the uterus, with the posed fetus.
The fluid now comforms to the fetus and the uterus, and will divide with the uterus division plane for any view I might choose in the future.
Material Development
I gave the fluid a slightly blue hue, to offset all the reds without making anything green or grey, and gave it a transparency. I set up lights in the scene that will catch the edges, to really sell the “liquid” effect. I find it quite pleasing to look at!
Redshift render of scene
Collision Issues
Since the umbilical cord was based on a rope object, I had the thought to add a collider to the fetal model so that the cord wouldn’t clip through. However, while animating Scene 2, I noticed the collider wasn’t working! Turns out a collider on a rigged&skinned model would only respect the original rigging position, not any of the animated positions – so the collider was on the t-posed fetus! To get around this, I temporarily made a volume builder and mesher object of an instance of the animated fetus, and gave it a bit of dilatation. I was able to then add an animated collider to that object, quickly cache the the movement of the umbilical cord rope object, then retire that CPU-heavy object. I love how versatile C4D can be!
Volume mesher with instance.
C4D screenshot of the fetus in a volume builder