Hello, As a beginner, I need your help on something. How can I prevent characters from crossing into each other. For example, when I try to put a character on the lap of another character, it goes inside. I don't want it to be like this. I want to show the pressure when he sits on his lap. I want the dent in the place where he sits to be obvious. Or, for the simplest example, to open the vagina when the penis enters the vagina, so that the penis does not look like one with the vagina.
I would be very grateful if you could direct me to any educational content or if you can share a sample video it would be very good.
It doesn't quite work the way you think. You have to manually move them until they appear to be touching, but this is not a game engine with collision detection. It's 3D rendering which basically takes a series of numbers and plots the resulting image they represent on screen without consideration for what else is in the scene. There are ways to tell it how one object or person can effect another, but they aren't perfect and can sometimes cause more problems than they solve. The best way is to just learn to adjust them until they appear to be touching. As some have suggested, smoothing modifiers can help if you want that appearance of one person effecting another but... that can be difficult. There are scripts and such available which can help (I can't think of them off hand, perhaps someone else can).
Even video games don't do the sort of collision detection you're thinking about. They usually use tricks like bounding boxes around a character to detect a collision between the two.
With practice you will get better at this. It took me a while, but I now do all my own poses and positioning manually. Daz has some nice tools to help with that. My favourite being the ActivePose Tool (Alt+Shift+P)...
You click it, then select body parts you don't want to move. So if I want to adjust an arm, for example, I will click their shoulders and press SPACE to lock them in place, click the chest and press SPACE to lock it in place, then click the arm or hand and drag it around to position it. It took some practice, but I use it A LOT now to get parts in place, then sometimes I will fine tune the positions with the dials after that. It's a very handy tool for posing and positioning once you get the hang of it.
Mainly, just... practice, practice, practice!