[osg-users] Fast cycling of textured rectangles

[Sebastian Messerschmidt]

Hi,
> Hi Sebastian,
>
> thanks for your input If I'd be switching texture binding, wouldn't 
> that mean that the scene still has to be rasterized before display? My 
> ultimate intention is to skip rasterization at all (i.e rasterizing 
> all patterns once at init) and just copy final pixels. Is that feasible?
Changing texture coordinates or switching binding is fast 
enough.Rasterizing has to be done in any case you want to put it to 
screen. I assume your patterns are images that you can pre-calculate, so 
sending them to the GPU is the matter of adding them to a texture 
object. Simply try it, it is really simple. Else, try to explain the 
problem you want to solve more detailed.

Cheers
Sebastian
>
> Best,
> Christoph
>
>
> Sebastian Messerschmidt <sebastian.messerschmidt at gmx.de 
> <mailto:sebastian.messerschmidt at gmx.de>> schrieb am Fr., 13. Nov. 2015 
> um 20:42 Uhr:
>
>     Hello Christoph,
>
>     You can use either a texture which contains all the textures and
>     modify the texture coordinates (so to say a matrix of different
>     textures).
>     Also texture arrays might help here a lot, if all the textures are
>     of the same dimensions.
>     Anyways, what you might you see are initial costs. Once the
>     texture is transfered to the GPU and your memory is not filled,
>     subsequent use should be a matter of switching texture units binding.
>
>     Cheers
>     Sebastian
>
>>     Hi everyone,
>>
>>     I'm working on a project where I need to display different
>>     patterns (textured rectangles) as quickly as possible. Currently,
>>     i have an osgViewer with a single view running that holds a
>>     single textured rectangle and upon user request, the texture /
>>     image is updated. This works quite ok, but requires a CPU->GPU
>>     transfer every time I intend to update the image.
>>
>>     I think there must be a way to improve performance when I know
>>     the set of patterns images beforehand. So, I would like to
>>     prepare pre-rendered textured-quads on the GPU and upon user
>>     request just cycle between those pre-rendered elements. That
>>     should reduce the CPU->GPU overhead to initialization time.
>>
>>     I somehow have the feeling that the solution requires a
>>     frame-buffer / render-buffer object per pattern and somehow
>>     involves glBlitFramebuffer to display the correct frame buffer,
>>     but I'm stuck in how to implement this in OSG.
>>
>>     Any kick start would be greatly appreciated!
>>
>>     Best,
>>     Christoph
>>
>>
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