[osg-users] nVidia HW: Lens Matched Shading, Single Pass Stereo - exposed in OpenGL?

[Sebastian Messerschmidt]

Hi,
> Hi Christian,
> I have the Single Pass Stereo working with ARB_viewport_array and and 
> a shader (attached). The required support for GL_ARB_viewport_array is 
> on the osg-submissions list. I have not done any work on the culling 
> yet, as the eyes are sufficiently close together to get a decent 
> impression of performance. bringing in light render passes would 
> probably require a smart adaptation of the cull frustum.
> The nvidia stereo_view_rendering seems to be to limiting for my 
> purposes, as I think it requires the display to be aligned with the 
> eyes, and we are working with head-tracked systems where the user is 
> able to rotate their head.
The big deal about this extension is that the vertex and geometry shader 
isn't invoked twice. This might quite save a bit if you are limited at 
the those stages. But thank you for the example.

Cheers
Sebastian
>
> Regards, Laurens.
> in the vertex shader do:
> gl_Position = gl_ModelViewMatrix * gl_Vertex;
> instead of
> gl_Position   = gl_ModelViewProjectionMatrix * gl_Vertex;
> For the rest of the shaders I rely on the osg shadergenerator with 
> base shaders from osg-data.
> new osg::Shader(osg::Shader::GEOMETRY, "#version 450\n" "#extension 
> GL_ARB_gpu_shader5 : enable\n" "layout (triangles, invocations = 2) 
> in;" "layout (triangle_strip, max_vertices = 3) out;" "uniform mat4 
> transform_block[2];" "in vec4 vbasecolor[];" "in vec2 vtexcoord[];" 
> "out vec4 basecolor;" "out vec2 texcoord;" "out int gl_Layer;" "void 
> main(void) {" " for (int i = 0; i < gl_in.length(); i++)" " {" " 
> basecolor = vec4(1,1,1,1);" " texcoord = vtexcoord[i];" " gl_Position 
> = transform_block[gl_InvocationID] * gl_in[i].gl_Position;" " 
> gl_ViewportIndex = gl_InvocationID;" " EmitVertex();" " }" " 
> EndPrimitive();" "}" );
>
> On Thu, Jun 9, 2016 at 1:24 PM, Sebastian Messerschmidt 
> <sebastian.messerschmidt at gmx.de 
> <mailto:sebastian.messerschmidt at gmx.de>> wrote:
>
>
>     Hi Christian
>
>         Hi all,
>
>         has anybody looked at these new features of nVidia hardware?
>
>         Lens Matched Shading and Single Pass Stereo are using new
>         hardware and driver features that allow the GPU to perform
>         single pass transform+shading of up to 16 independent view
>         matrices.
>
>     Isn't the change-set of single pass stereo
>     (https://www.opengl.org/registry/specs/NV/stereo_view_rendering.txt)
>     shader only?
>     So basically we need the NV_viewport_array2 support on the
>     osg-side to implement it.
>     Btw.: How is the relationship between viewports and bound FBOs for
>     instance? Suppose I need to render to different MRTs for each
>     viewport? Can anyone point to a good example here?
>
>
>         This could accelerate OSG's stereo rendering, provided that
>         the features are exposed thorugh documented OpenGL extensions.
>
>         Also rendering of cubemaps for reflections and shadows could
>         be greatly accelerated (six views in one pass).
>
>     That would require some deeper changes in the culling/camera-setup
>     I suppose, as multiple frusta have to be taken into account per
>     draw-invocation.
>
>
>         Christian
>
>     Cheers
>     Sebstian
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