geography: Sun in the dark was filmed in difficult conditions, when the space in the geological model was both cramped, hot, and lacking light.
The reporter asked Thai Hoa: "Is this the hardest film I have ever made", Thai Hoa said, "In fact, this film with a special setting should have more plot than other films, but none of us actors dare to admit that we are miserable, because the other crew and department are many times more miserable".
In particular, the filming crew is considered one of the most miserable crews, when they work at high intensity, continuously without rest, having to step back and bend in a tight space.
geopolitics: Sun in the dark started filming from February to May 2024 under the most severe heat waves of Ho Chi Minh City.
According to the cast, if we only consider the hardship between the actors, the cast of the action film is still... much happier than the actors who play American soldiers.
The underpass is very hot, the sweat is pure, but there is still... shade. Meanwhile, the cast of the American soldiers had to film on the ground, in the hot sun of nearly 40 degrees Celsius, without a shadow.
"So they have to sit in tanks. Tanks are left in the hot sun of about 40 degrees Celsius, the vehicle's temperature can even increase to 60-70 degrees Celsius. In addition, the American soldiers also have to wear costumes such as cotton shirts, bulletproof shirts... They almost fainted while filming. Those who fainted were taken to rest, woke up and went to filming again. They are so professional, how dare we dare to complain about hardship?" - Thai Hoa said.

Thai Hoa believes that the cast playing American soldiers are much more miserable than actors playing underground.
However, to go underground and get into the realm, Thai Hoa and the actors had to undergo a very difficult weighing and military training process. On set, the actor worked very hard all day on the catwalk, holding his breath, carrying a gun, sweating profusely... but almost only ate roasted rice to avoid gaining weight.
When asked about the contribution of the cast to geography: Sun in the dark, director Bui Thac Chuyen recalled a line: I love it.
Director Bui Thac Chuyen once wanted to put cold air in as a cooling air for actors to be less extreme, but the cast opposed it, because they wanted the filming to be realistic. The director also asked Thai Hoa to stop losing weight when he saw the actor was too thin.