So, it's in net.minecraft.client.renderer.entity.RenderMinecart: 39

long i = (long)par1EntityMinecart.entityId * 493286711L;
i = i * i * 4392167121L + i * 98761L;
float f2 = (((float)(i >> 16 & 7L) + 0.5F) / 8.0F - 0.5F) * 0.004F;
float f3 = (((float)(i >> 20 & 7L) + 0.5F) / 8.0F - 0.5F) * 0.004F;
float f4 = (((float)(i >> 24 & 7L) + 0.5F) / 8.0F - 0.5F) * 0.004F;
GL11.glTranslatef(f2, f3, f4);

Can anybody explain what is this?

Theres so much stuff like this inside the minecraft code, things that doesn't make sense at all.

I have no better guess than diesieben07 as to why that code is there

That's the weirdest piece of code I've ever seen... And this is coming from someone who's trying to subclass net.minecraft.block.BlockRailPowered at the moment.

it looks like this will generate small values which will be used to translate de minecart by a small amount...but since the seed is the entityid that means the randomly gwnerated position will be different for every minecart but will never change for a specific minecart .... idk this code goal seems to make every minecart look different but by such a small amount that no one would even notice the difference... at least i never saw the difference .

This is probably a poor work-around to handle rare cases where minecarts would be at the same place simultaneously.

So that a player would see it.