Triangles have two sides.  The front and back sides are determined using winding, that is, the order in which the vertices are given.


It is possible to give the front and back sides of the polygon a different appearance, or even not render the back side!

By default, OpenGL assumes triangles with a counter-clockwise winding are front facing.  This can be changed to clockwise using glFrontFace(GL_CW); and back again using glFrontFace(GL_CCW);

High

Exercise:
For triangle T1, which windings produce a counter-clockwise front face that is outward facing?

• A: {v3, v0, v1}
• B: {v0, v3, v1}
• C: {v0, v1, v3}
• D: {v1, v3, v0}