[osg-submissions] Multiple Render Targets

[J.P. Delport]

Sorry, re-read the example. With --image you should get a yellow quad 
with a smaller cyan quad in the center. The default read-back is texture 
0 (red) and the image callback halves its contribution.

jp

J.P. Delport wrote:
> yes, sorry, I'm not sure where to place the "what should I get" in the 
> example (on screen, in the --help?).
> 
> The yellow quad is what is expected.
> 
> A few things you could try:
> 
> If you run with --image, you should (without modifying the example) get 
> a washed-out yellow quad with a smaller yellow quad inside.
> 
> This is the same effect as in osgprerender: a render target is read back 
> as an image and the middle is modified.
> 
> If you search for "tex_to_get", you can select which of the 4 targets is 
> read back and changed, this will change to colour of the center smaller 
> quad.
> 
> Without --hdr what basically happens is:
> RT0 = vec4(1,0,0,1)
> RT1 = vec4(0,1,0,1)
> RT2 = vec4(0,0,1,1)
> RT3 = vec4(0,0,1,1)
> 
> output quad = RT0 + RT1 + RT2 -0.5*RT3
> 
> therefore the washed-out yellow result.
> 
> With --hdr the values are made very small (too small to fit into 
> FLOAT16) and then combined in the same way (RT0 is also made negative). 
> This is a basic test for MRT with FLOAT32.
> 
> If you search for shaderSource in the example, you'll see the simple 
> shaders. Reading them would prob explain it better than I can.
> 
> regards
> jp
> 
> Robert Osfield wrote:
>> Hi J.P,
>>
>> I've just done a quick merge of your changes (and committed the typo
>> fixes) and have run the osgmultiplerendertergets example but don't
>> know whether its working as all I get is yellow quad.  I have a 7800GT
>> on this machine.
>>
>> What should I expect?
>>
>> Robert.
>>
>> On Wed, Apr 2, 2008 at 10:09 AM, J.P. Delport <jpdelport at csir.co.za> wrote:
>>> Hi Robert,
>>>
>>>  following the discussion yesterday on osg-users, I have decided to submit
>>> the original patch as is.
>>>
>>>  MRT is enabled by an explicit call on osg::Camera (setDrawBuffers), just
>>> like readback of textures/images is enabled by osg::Camera->attach.
>>>
>>>  To me, the camera seems the natural place for these things at the moment.
>>> If it would make sense as a StateAttribute (either for Camera or FBO), the
>>> implementation is left as a possible future enhancement.
>>>
>>>  regards
>>>  jp
>>>
>>>  old message
>>>
>>>  ----8<----
>>>  Attached are the changes to OSG's Camera and RenderStage.
>>>
>>>  Camera got a new method called setDrawBuffers (instead of the normal
>>> setDrawBuffer), which mirrors the OpenGL extension glDrawBuffers.
>>>
>>>  setDrawBuffers takes a vector of BufferComponents and this vector is then
>>> translated in RenderStage to a vector of GLenums that is passed to
>>> glDrawBuffers.
>>>
>>>  The new calls are orthogonal to current use cases, so hopefully no other
>>> code/examples would be affected.
>>>
>>>  The attached example shows sample usage. The example is very contrived, but
>>> I hope it explains the concept. I have some other examples that I can
>>> contribute later.
>>>  ----8<----
>>>
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