On Fri, Jan 10, 2014, at 05:55 AM, Filipe Tomaz wrote: > Thank you (and Kirk) for showing the write direction. > > This bug only happens in lathes that the user uses the .axisrc like > described in: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?BackToolLathe > > Not sure the number of people using a lathe with backtoopost, so I am > unaware if this issue is relevant. > > In this case, for any tool with diameter != 0, the backplot does not > displays the tool. It simply shows some points on the screen, that flick a > bit. It is like the tool is being drawn, but is not able to. > I changed a lot of code for nothing, that I found out that the problem > is not on the linuxcnc code (this is, all the points are correct), but > rather the GL_TRIANGLE_FAN is not displaying correctly the points. I do > not know way, but I suspect it have something to do with the initial point > of the triangle fan. Unfortunately I do not know so much on opengl. To > prove my statement, I transformed all the TRIANGLE_FAN into lines (using > the same coordinates), and NOW THE TOOL PREVIEW IS DISPLAYED. > > Please take a look into the two images, below, that compares both > situations. > > http://postimg.org/image/qxmnr36ct/d82a4084/ > http://postimg.org/image/y5fge18m1/df9ac6b8/ > > Filipe
This is just a guess, but I think that openGL primitives like triangles have two sides. One is intended to be the outside, and is visible, and the other is intended to be the inside (for example, of a pyramid made from triangles). The hidden surface removal algorithms know that if the "outside" is facing away from the camera, they can treat the surface as hidden, and they don't bother rendering it. I think the decision about which side is the inside is based on the order that the points are specified, and maybe when you mirrored things you confused it? Again, just guess, and I might be totally wrong. -- John Kasunich jmkasun...@fastmail.fm ------------------------------------------------------------------------------ CenturyLink Cloud: The Leader in Enterprise Cloud Services. Learn Why More Businesses Are Choosing CenturyLink Cloud For Critical Workloads, Development Environments & Everything In Between. Get a Quote or Start a Free Trial Today. http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
