sketchup is good... but its performace to object (triangles) is appalling, especially if you dont use components (used since ver 1). but its a good sketch tool, for simple 3d objects to take else where, but can perform better with a few tips.
if you want a few more tips.
1. dont get bogged under in detail, think how big will this bit be when i render it, how many pixels is the computer going to have to show this.
2. dont draw object draw shadows, and sometimes, in fact alot the shadow is a texture, not geometry.
3. keep textures low res mine a are 1024 x 1024 (this is for easy PC ram access, all textures are 256 x, to help gpu blit) and also how big will it be on screen
i have soo much more i could tell
and dont mind as i knowledge is crap when kept to self
so lets look at what i meen in real terms.
take a look at few real world examples,
A railing in the back ground drawn with cylinders would be 32 facets around, but in the final picture only 3 or 4 pixals wide, thus it can be octagnal (sooryy speeling not strong point) to get a highlight, flat and shadow, rest is not needed unless the railing is foreground, and the subject.
A building in most maps is only a point roof box
and with enough pointy roof boxes we get a town for a distance (like impresionist art) so use textures for detail and draw a pointy box
Modular is your freind the walled castle i buit is only 1 wall, 1 tower, 1 gatehouse and a keep, then pointy boxes. and those are modules that i put toghere (a dormer, a bay window, a pointy box
) and the tudor style only used 4 (1024x1024) textures for all of them
same with the stone buildings (square windows) and stone2 (pointy windows), the differacne in gemoatry is only that tudor neaded overhang (shadow) and stone did not (but various gables etc)
hope that also helps kept it unsoftware sperfic.. but can do detail (frist 3d drawing was on a 486DX.... ohh my, not sure on ages here but if you dont know ask your dad
)
Many thanks