Hi Preet,
The OSG provides more than just support for passing data to OpenGL, it
does culling and this requires knowledge of the bounding volume of the
object. I would recommend sticking with using the standard
osg::Geometry::setVertexArray(..) for passing in the vertex positions
of your data so that the OSG can compute the bounding volumes
automatically for you.
Robert.
On 30 June 2012 08:02, Preet wrote:
> Hiya.
>
> I'm trying to pass attributes to my vertex shader, but have come
> across several issues.These issues only occur when I use OSG -- if I
> try to do the same thing with straight OpenGL calls, it works fine.
> I've set "setUseModelViewAndProjectionUniforms(true)" and
> "setUseVertexAttributeAliasing(false)". I add vertex attributes to my
> geometry by calling "setVertexAttribArray". I don't explicitly specify
> any other arrays (I don't call "setVertexArray" or anything like
> that).
>
> * Assigning a position attribute to '0' works as expected and my
> geometry shows up. Moving that position attribute to another slot
> doesn't work. I explicitly call "setCullingActive(false)" on my
> geometry and set zNear zFar on my camera but when I try to render the
> scene I get what I think are scene culling related issues:
>
> cull_draw() 0x15cd420
> _clampProjectionMatrix not applied, invalid depth range, znear =
> 3.40282e+38 zfar = -3.40282e+38
> end cull_draw() 0x15cd420
>
>
> * I also tried playing around with a normal attribute. I just take the
> normal and pass it as a varying to the fragment shader where it
> directly sets the fragment color to the value of the normal. I get a
> sane result when I set the normal attribute to slot 1,2 or 6 or 7. If
> I set the normal attribute slot to anything else I get random gray
> shapes obscuring the viewport:
>
> normal attribute set to slot 1: http://i.imgur.com/C5MQ7.png
> normal attribute set to slot 4: http://i.imgur.com/5tGoS.png
> same scene in app that uses straight opengl calls:
> http://i.imgur.com/C5MQ7.png (note that the normal values are
> different as well, I don't know why this is as I pass in the same
> values to both)
>
> So, does anyone know what's going on? Why can I arbitrarily set
> attributes to whatever slots I want in my 'raw' OpenGL program, but
> not with OpenSceneGraph?
>
>
> I'm using OpenSceneGraph 3.0.1 with an Nvidia card that supports
> OpenGL 4.2 on Linux.
>
>
> Preet
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