the latter allows explicitly specifying channel nr/ format. Also we no
longer have to manually manage an extra rendertarget any more.

replace to CV_Assert_N()

enables an ordered chain of full-screen post processing effects

`near` is an illegal variable name on Windows (if `windef.h` is included),
because a macro with the same name is defined.

Someone else already put your rage into words, see
http://lolengine.net/blog/2011/3/4/fuck-you-microsoft-near-far-macros.

also remove superficial CS conversion in fixCameraYawAxis

by keeping Camera oriented in OpenCV conventions instead of doing the
conversion for each SceneNode.

the latter assumes centered FOV, which is not the case

so we can use the alpha channel for e.g. masking

useful when uchar precision is not enough

also set the intrinsic in the AR demo

to prevent console spam. only outputs errors/ warnings now.