There is something wrong when rendering with optix

First please look at two pictures. They were rendered with optix.

The two pictures are about a tank is running through a mountain land. I just got one frame of the video. Obviously there is something wrong with the second picture, the mountain didn’t get rendered correctly. The only difference between the two pictures is the model of the tank, the tank in second picture is half size of the first tank.
I just can’t understand how it happened, I think if the model in the second picture is too small, the tank should have been rendered wrongly other than the mountain. Is there anyone who can solve my problem? Thank you very much.

Could be a lot of things, but if it’s related to model size you should analyze your overall scene size and put that in relation to floating point accuracy.
If you’re shooting shadow rays or any other secondary rays, this might be self intersection with the same geometry you’re starting the ray from.
If you’re using a scene epsilon to offset that secondary ray, increase its value. Just for debugging, try setting it to zero to see its effect. This method is very scene size dependent.

No, I didn’t calculate the secondary ray, the color of the models is determined by the energy they emit, as you know everything will emit energy as long as its temperature is above absolute zero. So in this model I didn’t take the reflection into consideration, the secondary light doesn’t exist. And external lighting source is also omitted.

All image links you posted don’t seem to work anymore. You could attach images directly to this forum by using the small paper clip icon in the top right of one of your submitted posts.

Secondary rays was just one of the possibilities.
Scene sizes outside a reasonable floating point precision range is still the first thing which comes to mind.