Adds a triangle to the batch, with a colour and texture coordinate for each corner.
immediate_triangle :: (
p0: Vector3,
p1: Vector3,
p2: Vector3,
c1: Vector4,
c2: Vector4,
c3: Vector4,
uv0 := Vector2.{},
uv1 := Vector2.{},
uv2 := Vector2.{},
normal := Vector3.{ z = 1 }
)