a small picture worths more than words... it often/always happen with some kind of props or figures (those especially made of primitives, or in some modelling softwares), when i turn the cartoon with line mode (need for anime doll renders) i have also bugs related to prop 3d modellign but it is not same bug in the meaning of the word.. but THIS: whenever i change slightly the camera angle it can dissapear, be less visible or fully waste the picture...