CGTalk - Feedback camera data to quad surface

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nineX

01-24-2007, 07:16 AM

Hello all,
I know of a shader or plug that does this particular
task.

I want to feed the view of the current scene onto a object,
a sort of loopback of the current view onto a given quad.

Ive been looking for a solution. I just thought it was possible
becuase this function exist in many VJ software, so I know it
can be done and fairly easilly since the current camera data
already exist, of course the actual viewing of the given scene
on the Quad using raytrace effects would not be possible until
a final render but Realtime mapping effects, ie viewport views
Open GL ect should be possible to access and map to a quad
and in realtime no less. I use VVVV as well. This is a built in
function and assist with creating wonderful feedback effects
without creating uneeded geomtry 4 quads feedback can generate
quite a bit of "illusional" scenery. Assuming a quad is texture
mapped as well with alpha ch extradonary graphic effects can be
achieved. I believe in all gets calculated on the GPU since it
it only calculating viewport views ( when not rendered ).

here is a sample although not the greatest of a feedback effect on a
small array of quads from VVVV

here (http://vvvv.org/tiki-browse_image.php?imageId=1299&highlight=feedback)

Incase the link isnt working,
http://vvvv.org/tiki-browse_image.php?imageId=1299&highlight=feedback

Any help would be appreaciated.

Best to all,
jay

Srek

01-24-2007, 12:10 PM

I just thought it was possible
becuase this function exist in many VJ software, so I know it
can be done and fairly easilly since the current camera data
already exist,
It might exist in your VJ software since it the raw material is already available, this does not hold true for a 3D app where the raw material is created in first place.
The reason why the function exist in your VJ software is that it's the correct place where to apply such an effect.
If you realy have to do it in the 3D app you will need to render one movie after the other and reuse the result of the former as a texture in the next etc. etc.
It a hen / egg problem that simply does not exist for your VJ software.
Cheers
Björn

FrankBerg

01-24-2007, 07:33 PM

Hi jay,

This is possible with some scripting in C4D.
you have to do it like VVVV does it: render a frame to texture and load it again the next frame on the Quad.
So assigning a material to the quad and load the previously rendered image in one of the channels of the material.

There is a Feedback tutorial @ C4DCafe by 3DCrew that does this technique automated by a coffee script.

Hope this helps and good luck, frank

LucentDreams

01-24-2007, 07:49 PM

I believe Per anders made a simple shader that does this.

Per-Anders

01-24-2007, 08:30 PM

yes, i seem to recall that, but can't remember where the shader is, it's probably somewhere in these forums if you do a search, it was very very simple.

nineX

01-25-2007, 01:08 AM

You guys are great and very quick to respond. Yes I know this effect
is in fact possible, as it impossible to work with Open GL without making
calls to various classes that are used in screen drawing.

Going the route of coffie would be delightful but only if neccesary, as
my work is becoming indeed more complex.

I have confirmed the tutorial on C4D 3D Cafe for users who are looking for
simular information the tutorial is here:

Click me (http://www.c4dcafe.com/ipb/index.php?automodule=downloads&showfile=83) (after you become a member)
Or
http://www.c4dcafe.com/ipb/index.php?automodule=downloads&showfile=83

thanks again, I will research this information further and I will certainly
delve deeper into the coffie scripting language.

Have a great day.

Srek

01-25-2007, 06:48 AM

you have to do it like VVVV does it: render a frame to texture and load it again the next frame on the Quad.
This would give you an offset of one frame for each instance and would need a pre computation of as many frames as you want to see echoed. From what i understood from the original poster this is similar to what he wanted but not the effect his VJ software allows him.
Cheers
Björn

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