Re: [osg-users] Problems with osgUtil::TangentSpaceGenerator
Daniel Borchart writes: > > Hi, > > I'm trying to implement a bump mapping shader. That works well for a simple shape like that plane, where I > define the tangent attribute manually: > > Code: > Geometry* plane = new Geometry(); >Vec3Array* vertices = new Vec3Array(); > Vec3Array* normals = new Vec3Array(); > DrawElementsUInt* faces = new DrawElementsUInt (PrimitiveSet::TRIANGLES, 0); > Vec3Array* texcoords = new Vec3Array(); > Vec3Array* tangents = new Vec3Array(); > > vertices->push_back(Vec3f(1.0f, 0.0f, 1.0f)); > vertices->push_back(Vec3f(-1.0f, 0.0f, 1.0f)); > vertices->push_back(Vec3f(1.0f, 0.0f, -1.0f)); > vertices->push_back(Vec3f(-1.0f, 0.0f, -1.0f)); > > normals->push_back(Vec3f(0.0f, -1.0f, 0.0f)); > > texcoords->push_back(Vec3f(1.0f, 1.0f, 1.0f)); > texcoords->push_back(Vec3f(0.0f, 1.0f, 1.0f)); > texcoords->push_back(Vec3f(1.0f, 0.0f, 1.0f)); > texcoords->push_back(Vec3f(0.0f, 0.0f, 1.0f)); > > faces->push_back(0); > faces->push_back(1); > faces->push_back(3); > faces->push_back(3); > faces->push_back(2); > faces->push_back(0); > > tangents->push_back(Vec3(-1,0,0)); > > plane->setVertexArray(vertices); > plane->setNormalArray(normals); > plane->setTexCoordArray(0, texcoords); > plane->addPrimitiveSet(faces); > plane->setNormalBinding(Geometry::BIND_OVERALL); > > plane->setVertexAttribData(6, Geometry::ArrayData(tangents, Geometry::BIND_OVERALL)); > > But for more complex shapes I have to use the TangentGenerator. When I try to run this: > > Code: > ref_ptr tsg = new osgUtil::TangentSpaceGenerator(); > tsg->generate(plane, 0); > > I get an "Debug Assertion Failed" with "Expression: vector subscript out of range" in generate(). > > Did I forget something? I cannot see the fault. > > Daniel > > -- > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=35575#35575 > > Hi Daniel, I come up against the same problem of utilizing osgUtil::TangentSpaceGenerator in the same way. I trace into TangentGenerator.cpp then I find that on line 223 the subscript of normal array(nx) is out of range when there is only one normal in it. TangentSpaceGenerator is assumed to work for normal binding of BIND_PER_VERTEX instead of BIND_OVERALL. So you have to set normal for EVERY vertex. If I miss something, please let me know. Guo ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Shader Update Latency?!
Robert Osfield writes:
>
> Hi Thorsten,
>
> By default the OSG computes the near/far planes on the fly during the
> cull traversal on every single frame. You can disable this.
> Alternatively you could just use the gl_ProjectionMatrix directly on
> the GPU to get the near/far planes - this is how I'd do it, far more
> flexible and never needs any additional uniforms or callbacks.
>
> Robert.
>
> On Wed, Dec 1, 2010 at 6:15 PM, Thorsten Roth
> wrote:
> > Hi,
> >
> > I currently have a problem with a shader update callback I do not
> > understand. I have a vertex and fragment shader which calculate linear
depth
> > in [0,1] for me, also respecting dynamic clipping planes. To achieve this,
I
> > pass zNear and zFar as uniform parameters to the shader. To have them
> > updated, I have the following callback methods (zFar is looking
> > accordingly):
> >
> > class UpdateShaderZNear: public osg::Uniform::Callback {
> > public:
> > virtual void operator()(osg::Uniform* uniform, osg::NodeVisitor* nv)
> > {
> > double x, zNear;
> > viewer->getCamera()->getProjectionMatrixAsPerspective(x,x,zNear,x);
> > uniform->set((float)zFar);
> > }
> > };
> >
> > Now when I move my camera towards and away from the object, it seems like
> > the shader update is one frame (or so) "too late", as I get values that do
> > not correspond to the [0,1]-normalization and the problem disappears as
soon
> > as the camera stops.
> >
> > Is there any reason for that/does anyone have an idea what I'm doing wrong?
> > If more information or code is necessary, just tell me
> >
> > -Thorsten
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> >
>
Hi Robert,
I encounter a similar latency problem when I try to update a uniform using
camera's view matrix in the uniform's callback. Since this uniform is needed
to compute only once per frame, I decide to compute it on CPU before it's
submitted to GPU.
It seems that when the uniform's callback is called, the camera has not been
updated yet, right?
Currently I solve this problem by updating the uniform in a PreDrawCallback of
the camera. But is this a graceful way to achieve it?
Thanks in advance.
Guo
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