[vtkusers] What Is Off-Screen ?

[Sylvain Jaume]

Mark,

I'd like to add this:

Currently you can do offscreen rendering on Linux with hardware 
acceleration but a window will pop up. To avoid this, you need to link 
VTK with Mesa *and* turn on the OSMESA option when configuring VTK with 
CMake.

In the vtkOpenGLHAVSVolumeMapper, offscreen rendering means that the 
rendering happens in a framebuffer object smaller than or equal to the 
screen size. As a final step, the colorbuffer of this framebuffer object 
is mapped to the full size of the screen. This allows image-based 
level-of-detail to meet interactive rendering.

For references about the HAVS algorithm and the level-of-detail 
algorithm, I'd point you to these papers:

"Hardware-Assisted Visibility Sorting for Unstructured Volume Rendering" 
by S. P. Callahan, M. Ikits, J. L. D. Comba, and C. T. Silva, IEEE 
Transactions of Visualization and Computer Graphics; May/June 2005.

"Interactive Rendering of Large Unstructured Grids Using Dynamic 
Level-of-Detail" by S. P. Callahan, J. L. D. Comba, P. Shirley, and C. 
T. Silva, Proceedings of IEEE Visualization '05, Oct. 2005.

Sincerely,
Sylvain

Sylvain Jaume wrote:
> Hi Mark,
> 
> Setting OffScreenRenderingOn() on your vtkRenderWindow will not display 
> the rendering. Note that on Linux you need to link VTK with Mesa.
> 
> Sincerely,
> Sylvain
> 
> JohnMark wrote:
>> Hi , everyone ,
>>        I always see that this is off-screen technique and so on when I 
>> read some information of VTK
>> classes , for example vtkHAVSVolumeMapper . but I really don't know 
>> what is off-screen technique and why
>> we have to use it . and now I have searched a lot of information , 
>> however , they all say that they use
>> it , but I cann't get what it is in detail .
>>        so can you help me to give me some hints , information , or 
>> articles ?
>>  
>>     thank you with great regards !
>>  
>>     Mark
>>
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