In OpenGL the "default direction" for triangles is CCW. Makes sense. However, ...is there a standard direction like that for line-strips/polygons? .....I have polygons that are built up from many triangles. It feels more natural to have the points of the line-strip ordered clockwise but I wanted to know if theres a standard for that or it doesnt matter.
Polygons: clockwise or counterclockwise
Crossbones+ - Reputation: 7006
Posted 18 May 2013 - 04:48 PM
Winding order is used for culling backfaces. So that's why there needs to be an established convention. But you need at least 3 vertices to do that (to calculate a normal that indicates whether something faces in or out of the screen), so it doesn't really make sense for lines.
Members - Reputation: 1455
Posted 18 May 2013 - 05:19 PM
Thanks. I was not precise. ....my English. I draw a polygon with the mouse. Which is practically a closed polyline/line-strip. Sometimes I need to reorder the points so the polygon is always "drawn" the same direction. (I dont draw the polygon directly, I build it up from triangles. The triangles are drawn CCW.) Should the points of the polygon ordered CW or CCW?