[vtkusers] 3 speed questions

Tue Nov 9 10:55:31 EST 2010

My data is about 512*512*100 and the meshes are contained within the data.
 The thing that was weird to me is that the render speed is the same whether
or not I decimate the mesh.  I tried decimating the mesh by .999 and the
speed was just as slow.  How can I inspect my pipeline for
any weirdness that I might be doing?

On Mon, Nov 8, 2010 at 8:59 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Jonathan,
>
> Turning on wireframe will usually slow down the rendering (but in this
> case, since you are rendering just 2D contours, it might not make a
> difference).
>
> But I suspect that it isn't the rendering itself that is slowing you
> down, I think that the slowdown is the result of undesired VTK
> pipeline execution within the Render call.  The reason I say this is
> that modern 3D graphics cards can draw over 100 million triangles per
> second, and assuming that your voxel data is around 256*x256*256, your
> meshes will have approximately 500000 triangles and your graphics card
> will be able to draw them at over 200 frames per second.
>
> So either your meshes are much larger than my estimate, or else
> something is happening in the VTK pipeline to cause the mesh to be
> re-generated at every render.
>
>  David
>
> On Mon, Nov 8, 2010 at 9:15 PM, Jonathan Morra <jonmorra at gmail.com> wrote:
> > Is there anything I can do to speed up the Render time?
> >
> > On Mon, Nov 8, 2010 at 8:13 PM, Karthik Krishnan
> > <karthik.krishnan at kitware.com> wrote:
> >>
> >> On Tue, Nov 9, 2010 at 2:54 AM, Jonathan Morra <jonmorra at gmail.com>
> wrote:
> >> > More information that I've found about the first issue I reported.
>  I've
> >> > been narrowing down the issue, and the issue appears to be with
> >> > vtkImageViewer2.SetSlice(int slice).  This method is very slow when
> I'm
> >> > rendering a vtkPolyData that represents a mesh (whether it's cut or
> not
> >> > is
> >> > actually irrelevant)
> >>
> >> Contrary to what you assume, It is relevant. The SetSlice method
> >> internally invokes render, so as to update the display in response to
> >> changes. A "Render" implies that everything displayed on this
> >> renderwindow is re-rendered. This includes the rendering the polydata.
> >> If uncut, it can be slow depending on the number of cells. If cut, it
> >> can take time to update the cutter, since the cut-function (plane) has
> >> been translated.
> >>
> >> > and fast when I'm rendering either nothing or a
> >> > vtkPolyData that represents a stack of 2D contours.  Does this help at
> >> > all?
> >>
> >> Indeed, as mentioned above, there is no cutting to perform here.
> >> Rendering a bunch of 2D contours is probably faster than rendering
> >> your entire mesh.
> >>
> >> >
> >> > On Mon, Nov 8, 2010 at 10:26 AM, Jonathan Morra <jonmorra at gmail.com>
> >> > wrote:
> >> >>
> >> >> Thanks for your response.  It turns out on my machine that that
> >> >> initialization is too slow.  What's happening is the following
> >> >> 1.  The user click indicating that they want to try a contour
> >> >> 2.  A new vtkContourWidget is made with the dijkstra interpolator.
> >> >> 3.  The contour widget is initialized as I described above with just
> >> >> two
> >> >> points.  Adding that second point is where the slowdown occurs.
> >> >> As far as point 2, I am initializing a contour widget with the output
> >> >> of
> >> >> vtkCutter, but I am subsampling when I do that (I take 7% of the
> >> >> points), so
> >> >> I only have a handful of control points.  Is there a way to frontload
> >> >> the
> >> >> load time so I only have to do it once as opposed to every time a
> user
> >> >> wants
> >> >> to draw a contour?  That is simply too slow for my application.
> >> >> Also do you have any idea why rendering the meshes is slow?  Could it
> >> >> be
> >> >> related to the point order, or is is something else?
> >> >> On Sat, Nov 6, 2010 at 8:54 AM, Karthik Krishnan
> >> >> <karthik.krishnan at kitware.com> wrote:
> >> >>>
> >> >>> On Tue, Nov 2, 2010 at 6:31 AM, Jonathan Morra <jonmorra at gmail.com>
> >> >>> wrote:
> >> >>> > on vtkDijkstraImageContourLineInterpolator and am able to
> >> >>> > successfully
> >> >>> > create the contour widget with live wire interpolation. However,
> >> >>> > when I
> >> >>> > first initialize the contour with the following code it is very
> slow
> >> >>> >     // For now, we're just initializing the data with
> >> >>> >     // the point that was clicked
> >> >>> >     vtkPoints points = new vtkPoints();
> >> >>> >
> >> >>> >     // The initial data MUST be at least a "line"
> >> >>> >     // by giving the same point twice we are effictively creating
> a
> >> >>> > zero
> >> >>> >     // length line
> >> >>> >     points.InsertNextPoint(lastContourControlPoint);
> >> >>> >     points.InsertNextPoint(lastContourControlPoint);
> >> >>> >     vtkPolyData initialData = new vtkPolyData();
> >> >>> >     initialData.SetPoints(points);
> >> >>> >     contourWidget.Initialize(initialData, 0);
> >> >>> > The line that is slow is the last line.  The weird part is that if
> I
> >> >>> > do
> >> >>> > not
> >> >>> > use live wire, and just use the default Bezier curve interpolation
> >> >>> > the
> >> >>> > initialization is instant.
> >> >>>
> >> >>> Yes. There are 2 issues here.
> >> >>>
> >> >>> 1. The dijkstra interpolator is a bit slow to start with, since
> during
> >> >>> the time of initialization, it builds the adjacency information. But
> >> >>> that's not a big deal when you are drawing on an image. The very
> first
> >> >>> line segment placement is a bit slow (~3 seconds). After that its
> fast
> >> >>> and interactive.
> >> >>>
> >> >>> 2. The real issue, I think, here is the fact that you are
> initializing
> >> >>> the contour with the contour with lots of control points. How many
> of
> >> >>> them are there ? As I understand, you are generating these control
> >> >>> points from the output of vtkCutter ? Perhaps you want to sample the
> >> >>> input polyline and then feed those sample points as the control
> >> >>> points.
> >> >>>
> >> >>> Thanks
> >> >>> --
> >> >>> karthik
> >> >>
> >> >
> >> >
> >
> >
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