[osg-users] Get current Billboard ModelView matrix?

Sebastian Messerschmidt sebastian.messerschmidt at gmx.de
Tue Jul 5 01:20:20 PDT 2016

Am 05.07.2016 um 10:05 schrieb Philipp Meyer:
> Hi,
> I want to track the delta movement of every fragment in my scene. Only tracking on a per object basis would not be enough because an object may, for example, rotate (so that one side of the object approaches the camera, the other side doesnt) or it may have moving parts.
That doesn't really make sense. An object will be rasterized into 
multiple fragments. Transforming it will create a completely different 
set of fragments. The only way to compare "two sets" of fragments is to 
give them a common propertry such as color/id etc.
You're simply not explaining what you are after, so it is really 
impossible to give you any advise on how to tackle your specific problem.
> You are talking about writing data on a texture. I would be very interested in how that technically works. Im still a beginner with shaders but I thought that the fragment shader can only write data to a very specific point on a texture (where the current fragment would appear), and depending on the alpha blending and other settings the final pixel color is determined by the hardware. How would I go about writing actual information to a texture via. a shader as you suggest?
You're right. When rendering to the target buffer you can only write to 
the fragments raster position. In compute shaders you can read/write 
arbitrarily (with certain performance penalties). But that is 
irrelevant, as long as you don't explain what you want to do.
If you're doing some RADAR simulation in terms of wave-propagation etc. 
you might be better of to use GPGPU-algorithms instead of rendering.  
But again, without a solid description of the problem at hand, it is a 
lot of guesswork...

> Thank you!
> Cheers,
> Philipp
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=68005#68005
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