big textures are not an big problem your videocard have to read it calculate it everytime you start inside the game,(big textures ask allot if your videocard need to read allot) , its the way how you prepare them. let your videocard cash the big textures!. are they compressed or not. compressed textures are lower in size than uncompressed. the problems comming from the shader use on it. like bump mappings on big textures ask allot more calculations. specular mappings all that stuff ask more on yout total(test it with texdif vs trainspecbump mapping). fast videocard do it better than a slower one. more memory more cash space.
you have to use always backface culling see google for details on this. dont put your miplod bias on minus to much. and all that parts. to much of this stuff ask preformence. polygones are the most killing part of a game and not only on railworks on every game today. and 3dmax users need to know this as the best. if you grow in polygones your viewport preformence go down. same inside a game.if this was not an issue we dont have to use lods on our models ? and why do we still use textures on game models ? bump mapping is designed for this small stuf on your objects to give an impresion of 3d. also for saving polygones/ geometry. for one loco with 50,000 its not an big issue, on lower spec computers a bigger problem, if you have a couple of them inside a close range than it will ask frames per seconds. allot more polygones are alot more faces that you need to render(allot more faces on big textures asking more than flat sufaces.!!! simple hold it low 50,000 is toooo much . hold 30,000 as maximum my talent running on 30,000 polygones and thats the full combination front midle back. looks it flat ? no it dont
lets go back to jml his nice model, no polygones anymore