[osg-users] RenderBin vs. SlaveCamera

[Sebastian Messerschmidt]

Hi Werner,

I'm using slave cameras only for certain multi-channel setups where I 
need multiple viewports rendering the same content with different 
frusta. For multipass applications (and I simply consider HUD to be a 
separate pass) I always use normal cameras (with absolute reference 
frame for fullscreen passes and relative for composing passes).

You can assign an explicit number to the camera order by using.

camera->setRenderOrder(osg::Camera::PRE_RENDER, pass_number);

I use the PRE_RENDER scheme, since all passes of my offscreen rendering 
need to complete before the output is presented. Given your scenario you 
could of course simply set the render order of your HUD camera to 
something high.

Setting up rendering order with the Geometry RenderBin seems akward, 
since the HUD geometry is supposed to be rendered by the HUD-camera 
only. So a slave camera might not be the best option (apart from the 
fact, that the HUD is supposed to have its own projection and 
transform-matrix).

hth
Sebastian

> Hi all,
> 
> I'm restructuring my project because I want to implement some multi pass 
> effects.
> I have some problems understanding the different approaches for example 
> when
> creating HUD displays.
> The approach I used so far is attaching a SlaveCamera and puttung it in 
> PostRender pass.
> On the other hand I found an approach of just attaching the matrices to 
> the root node and
> assigning the HUD geometry to a RenderBin with high number.
> 
> I'd like to understand the difference of the approaches and the pros and 
> cons.
> 
> Is there any one who can help me with that?
> 
> Thanks
> 
> - Werner -
> 
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