warning, Long post, bear with me.
I think the topic is about game developing and rendering, more than writing.
Part 1: What I've encountered and why I think is that way.
Like, most cases I've encountered; there is this sex scene, once the setup is complete (initial conversation and we are on the meat of the sex animation), unless you have rendered an atrocious quantity of camera angle and different positions, and because you don't want to force the player to watch the same animation for 20 minutes (more IRL like than 30 seconds of fuck) (even if there are a lot of cameras angles and different poses), you have to put the button to End. (Cum, in this case). Let's say your engine supports showing the button to end and playing the animation at the same time. More even, playing some random dialogue where the button is awaiting you to press. Maybe you can have on those button changes of positions, but, When you press it, all is over. (sort of Summertime Saga method)
Unless the dev forces you thru a long sex scene (multiple sex positions and relevant dialogue and not just a Change Camera angle button, (that you can only get out if the dev allows the MC to cum sooner, but maybe is not in the plans of the story because Important Submission Dialogue or wathever), in a sex scene (The sex animation exactly), you just can sit there watching, changing camera angle, or cumming.
So even if the sex scene is programmed, there is no easy solution to this; If the player is enjoying the scene/camera angles, the sex scene will endure more. If he's not enjoying it and want to ending, well, that will be a fast fuck.
but if the Dev not even integrates buttons to decide when to stop it, well, yes, as said, he's not gonna cram you 20 minutes of the same 1-3 camera angles, so MC is going to cum in 30 secs. (and this is for sure the worst method of coding a sex scene, unless is a story relevant fast cum)
Thing is, even with the effort of the dev to give the player the control, it is not gonna feel real, unless the main focus of the game is to make the sex scenes long and believable (and I didn't seen many of them yet; because that means dozens and dozens of different frames (not animations) of "let me put the knee over here", "fuck, you elbowed my stomach", "Wait a moment", "put the lights on a moment".
Part 2: my example.
Example in my Daz rendered game; I've been coding the last days a very long sex scene (specially long to code, because branching and making all different timing for image-fades and dialogue work in all the choices), not necessarily long to play):
Sex Animations starts with a handjob, and the girl wants for you to cum on her face. after a little dialogue while the animation plays, (is not like I can eternize every type of this scene with infinite dialogue or infinite number of different animations), a choice is given (in this case Continue or delay). Delay plays a small random conversation and the animation is drag on. If you continue, after some short words, you have another choice, Cum in her face as she desires, ask her to blow you, or tell her to stand up and get ready to get fuck.
(if you tell her to fuck well, let's say thats the second part of the coding hell sex scene, let's stick to the blow part).
So you decide to cum on her face, but don't worry, you have another load. Then she's cummed and keep making you a HJ because you're hard. Another choice appears; Ask her to blow you or ask her to fuck. (Now again, let's not talk about the fuck part).
So you tell her to blow you while she's covered in cum. There is not much dialogue to have here, she has her mouth full (well in my scene she tries to talk and the MC just tell her to not try to and focus). Some random MC dialogue, Choice, Continue or Delay, etc, then Choice, Cum on her mouth, or tell her to stand up and fuck (You only have two shots so if you cum again the sex scene is over for that day, choose a different thing next time).
So you choose to cum again.
Posing and rendering all the branching, coding and writing all the branching dialogue, coding the random dialogue to allow the player to delay and not get just an empty animation, coding the image transitions and fading and animations, keeping the variables if her face is cummed or not for the next branches, for the fuck scene...
It's a bit of work. And Even then, if the player power-runs all the choices... Continue -> cum -> blow -> cum, it sure is over in less than 5 minutes. Two cums in five minutes! And talking here about a complex sex scenes with options. Imagine if is just a sex scene where your choice is to doggy her.
PS: and I'm not trying specially to make sex scenes believable, I just like that sort of choices.
Conclusion:
-Coders, sex scenes need writing and coding love.
-Players, understand that you have to put your part of suspension of disbelief, but well, at least ask the coders to put a "choice when to cum" to not look like all is over in 20 secs xD
