#### 11.2.11 bdFacet

• bdFacet( <facets list>, [options] )
• Description: defines a facets list. bdFacet options are:
• backculling := < 0/1 >. Shows if the non visible facets have to be eliminated or not (0 by default). A facet is not visible if its normal vector is not in the direction of the observer.
• clip := < 0/1 >. Shows if the facets have to be clipped by the window defined with the option clipwin if clip is 1, or by the plane defined with the option clipwin if clip is -1 (clip=0 by default).
• clipwin := < [M(xinf,yinf,zinf), M(xsup,yup,zsup)] >. Defines the 3D window for an eventual clipping if clip=1, the window is then given by its great diagonal: [M(xinf,yinf,zinf), M(xsup,yup,zsup)] (this is the current window by default). But if clip=-1 the option clipwin is interpreted as a plane: [3Dpoint, 3D normal vector].
• triangular := < 0/1 >. Shows if the facets are triangulated or not ($0$ by default).
• addsep := < "x" or "y" or "z" >. That options, if it is not equal to Nil (default value), determine the englobing box of each facet and add in the list one of the faces of that box (the face perpendicular to the $Ox$ axis with $x$ minimal if the option value is "x"), that new facet will remain invisible and will be used as separation wall, therefore the “real” facet won’t be cut by a facet that is entirely behind the wall. That option is useless for convex objets.
• color := < couleur >. Defines the color (white by default).
• contrast := < positive number >. The ordinary contrast is $1$ (default value), a contrast set to zero means the color is solid.
• smooth := < 0/1 >. Shows if the GOURAUD algorithm (facets smoothing) has to be used or not at the pstricks or eps exports(0 by default). Warning, pdf viewers are slow to display those type of images !
• opacity := < number between 0 and 1 >. Opacity value (1 by default), permits to introduce transparency if opacity is strictly less than $1$.
• matrix := < 3D matrix >. Define a transformation matrix that will be applied on the facets (this is the identity by default). The transformation is done before an eventual clipping.
• twoside := < 0/1 >. Show if the front-back of the facets have to be distinguished. If yes, the two sides won’t be in the same color (1 by default).
• above := < positive number or zero >. Places the facets above the scene, translated with the vector above*500*\n ($0$ by default).
• border := < 0/1 >. Shows if the edges of the facets have to be drawn or not ($0$ by default).
• bordercolor := < color >. Edges color if border=1 (black by default).
• hidden := < 0/1 >. Shows that the hidden edges have to be drawn if border=1, if yes, then the variables HideStyle and HideWidth are used. By default, that option has the value of the general option hiddenLines.