Strange lines appearing when rendering glass My scene is a cube standing on a checkered plane. For some reason I don't quite understand, when i render the final product lines will appear on the cube, as seen in the picture:


What really bugs me is that I rendered another picture awhile ago, with pretty much the same settings (quite close at least) but this time no lines appeared! Unfortunately the blender file that came with this picture was deleted, making it impossible me to copy from:
The cube was intersecting with the floor which created this effect :


Select the object and hit G then Shift and move the mouse up slightly 
or you can enable face snapping and move the cube to place it on top of the floor plane 




Here is the render after moving the cube