LDraw.org Discussion Forums

Hallo,

in http://www.ldraw.org/library/primref/ the following is mentioned: "To avoid matrix arithmetic problems in some renderers, the third dimension ({y} in the default orientation) must be given a scaling factor of 1."

Is it that strict or is a -1 allowed as well?

The reason for the question is that I'm still working on 11767. If I fix the BFC and I mirror or rotate a primitive I get a -1 as scaling factor for y. Is it legal or is it prefered to have a 0 BFC INVERTNEXT statement for many lines of code?

regards, Ingolf

Both 1 and -1 are legal for flat primitives, yes.

The current version of DATHeader finds those "scaled flat subfiles" and will correct this.

If you use BFC the sign on the flat dimension will effect which face is displayed so if 1 shows the front -1 will show the back.

Quote:\"To avoid matrix arithmetic problems in some renderers, the third dimension ({y} in the default orientation) must be given a scaling factor of 1.\"

Actually I don't think that coefficient in flat direction does matter - except that it shouldn't be 0 (a lot of old LDraw part did have this issue), and of course sign impacts BFC as mentionned by Mark. But anyway we now have a tool that does care for us - thanks, Mike!