Hi David,
David Spilling wrote:
Note that doing (1) doesn't preclude RTT - e.g. you can RTT the whole
inverted scene to a texture and then generate appropriate texcoords on
the mirror, either "by hand" since your camera is fixed, or in a shader.
Plus I'm not sure why you think that (1) is "quite a few additional
render passes". Obviously with RTT it's only one more pass - the
inverted scene - but without RTT, and with a stencil buffer, you only
have to draw (a) the mirror, with stencil buffer set, (b) the inverted
scene respecting the stencil buffer, (c) the rest of the scene without
the mirror. Good control of your renderbins makes this fairly easy.
Additional issues with (1) might include the fact that you have to
manage the lighting (i.e. you have to invert the scene lighting as well,
otherwise it looks pretty odd). Also, an unlikely but possible issues is
that If you have some special requirements for poly winding - e.g.
models with special shaders - note that if you just mirror the scene,
all the winding inverts as well.
FWIW, I would do either technique as RTT, as then effects like blur, or
mirror surface non uniformity, or things like this become a lot easier
(in GLSL).
Given theat, I'm not sure I have a strong favorite. I guess I'd do (2)
since your camera(s) are fixed; you need a new camera to do RTT anyway
so setting it up inverted is easy. The only reason I might not is if I
want to play with complex camera settings later which might be a pain to
implement e.g. stereo, strange projections, etc.
Rendering performance should be near identical (assuming RTT for both).
thank you for this insight, it really helped a lot. I am using RTT with
a duplicate inverted camera now, as this seems easiest for the simple
effects I want to achieve. Currently, I am struggling with texture
coordinates and placement and masking of cameras in my scenegraph to
avoid introducing infinite recursion. Solving this will be just a matter
of time, though. ;)
Thanks again,
Alex.
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