I've been working on this mural of Tenaya Lake trying to learn the ins and outs of SL construction. This mural is actually made up of eleven separate prims or blocks. I did this both because there is a maximum image size allowed in SL and because I wanted slightly different animation in each of the blocks. The water in the distance needs a different ripple effect than the water closeup. The major problem I've had in assembling these blocks is the seam line between each of the blocks. In some of the joins there exists a dashed line, depending on viewing angle.

Last night I met a lady in SL that had been a resident there for several years and had experience building objects. She gave me a valuable clue on how to reduce the lines, the textures of the joining faces need to be transparent. She also advised that they should not be defined as white. It is also possible that if I define these blocks with a zero thickness the lines may go away. I haven't tried that. Currently the blocks are defined as 0.50 meters thick. I may try that next. Anyway, here is what the mural currently looks like. The ripple effect can only be seen when viewing in Second Life.