Hello Daniel,
I haven't had a chance to look at the code yet, thanks for providing the
test file though!
On 06/03/2011 10:43 AM, Daniel Weber wrote:
> I'm using OpenSG2.0 to read line strips out of a .wrl file and process them
> afterwards. I've attached a sample file containing three line strips. In
> principle these line segments are connected, i.e., they represent a closed
> curve. I have some trouble with the whole process and I do not know if there
> are bugs or I'm missing something.
>
> 1) When reading the file, GL_LINES instead of GL_LINE_STRIPS are generated in
> the geometry core. A simple example shows the issue: At the end of the
> following code snipplet, the type of the geometry core is GL_LINES instead of
> GL_LINE_STRIP.
hmm, that seems to be a case where the VRML loader/writer has taken a
shortcut and just does not attempt to create LINE_STRIPS where it makes
sense.
> I fixed that in my application by traversing the generated scene graph and
> replacing all GL_LINES with GL_LINE_STRIP.
that gives the expected visual result, but is a bit wasteful as you will
have line segments of length 0 in the strip.
> 2) In a second step I need to merge all geometry cores into one. As the
> geometry is spread over the whole the scenegraph and the GeometryMergeOp only
> works with direct children, I collected all geometry cores and put them
> "below" a group node ("newScene"). The merge operation works in principle,
> but it always results in two geometry cores: one with the merged geometry and
> another one. I assume that the "second" one is simply not deleted in the
> final step. Here is the code:
that does indeed sound like a bug.
> 3) In the third step, I call "createSharedIndex" in order to merge vertices
> that belong more than on line segment (these are the start- and end-vertices
> of the line strips.) With the attached file, only two of the three
> start-vertices are merged with the corresponding end-vertex. What may be the
> reason?)
>
> 4) Finally, I would like to make one linestrip out of the geometry. But the
> StipeGraphOp does not seem to work for linestrips (only tri- and quadstrips?)
yes, the striper only handles triangle strips.
In general the GraphOps are meant to perform optimizations that are
applicable to all models so they may not necessarily give optimal
results for specific cases like yours. That is not to say that the
behaviour you are seeing indicates bugs that should be fixed, just that
it may be hard to get the generic GraphOps to produce the exact result
you are expecting.
I would recommend considering to write your own GraphOp for the specific
scene/optimization you require. Merging Geometry that is known to only
contain line strips should not be very difficult and it's much easier to
get the optimal representation you are looking for that way than by
tweaking the generic code.
Cheers,
Carsten
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