Well, it requires at least 3 additional rendering passes: the grab of the
depth buffer, the grab of the color buffer and a polygonforeground with a
shader to render the result. The thing that probabily slows down the most is
the real-time mipmapping that opengl has to perform to the color buffer in
each frame.. furthermore, if you also want to blur/mipmap the depth buffer
to increase the accuracy of the effect, well.. things start to be a little
slower :) but I think it's worth a try.
2007/5/9, Marcus Lindblom <[EMAIL PROTECTED]>:
Neat!
Do you know how much performance impact does your technique have? I'm
thinking of implementing something similar to blur objects close to the
camera in our app (someday at least.. :)
Cheers,
/Marcus
Stefano wrote:
> I solved the problem, at last. The render had almost all the depth
values
> compressed in a very limited range due to the non linearity of the depth
> buffer. Once i I linearized that buffer using the following piece of
code
> into a vertex shader the problem disappeared.
>
> vec4 xx = gl_ModelViewProjectionMatrix * gl_Vertex;
> xx.z = xx[2] * xx[3] / zFar;
> gl_Position = xx;
>
> Thanks for your precious help Marcus.
>
>
> 2007/5/9, Marcus Lindblom <[EMAIL PROTECTED]>:
>>
>> Stefano wrote:
>> >>
>> >> Test some values to see if you are getting discrete steps, or simply
>> set
>> >> nearest_mipmap_nearest and see if it yields equivalent results.
>> > Here you have the results.. the first image is with
>> > GL_NEAREST_MIPMAP_NEAREST.. the second one with
>> > GL_LINEAR_MIPMAP_LINEAR -->
>> > http://steffoz.altervista.org/depth.htm
>> > I think the filtering is visible. So, if also the filtering is good,
>> what
>> > else could be? :(
>> Yup, there is filtering all right. I can't see if mipmap-filtering is
>> done though, but that ought to be there since you at least get
bilinear.
>> (However, I'm still not 100% convinced. :)
>> >> What card are you using btw? (Don't know if you've said that before)
>> >> I _know_ some cards don't filter depth component textures at all.
>> >> (The GF7800 doesn't, for instance.)
>> > I own a nv6600.
>> Right. I don't know much about that card though.
>>
>> You might want to try the OpenGL.org forums. I'm have the feeling this
>> isn't OpenSG related anymore, so there might be ppl there who knows
more
>> about this. Let us know if you figure it out. (Sorry for not being able
>> to help more.)
>>
>> Cheers,
>> /Marcus
>>
>>
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Stefano Verna
mail/gtalk: [EMAIL PROTECTED]
skype: steffoz
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