In Jain Dharma, mere accidental seeing of a naked person is not by itself a sin if there is no lust, attachment, or malicious intent.

But for a layperson (śrāvaka/śrāvikā), deliberately looking at nudity is generally not considered proper conduct, because:

• it can stimulate passions later,
• it may reflect carelessness in restraint,
• and it can weaken the spirit of brahmacharya and self-control.

So the key points are:

• No sexual desire, no attachment, no intention → the karmic fault is much less.
• Deliberate viewing → still not ideal for a Jain layperson, even if desire was not felt at that moment.
• Jain ethics values not only the action, but also the inner intention and vigilance.

In short: not necessarily a major sin if there was no lustful intention, but deliberately doing it is still against the spirit of restraint for a lay Jain.