From the code fragment all 'num_points' is doing is presetting the expected
number of points in the object so it can pre-allocated the point array, etc.
In the case of the sphere it pre-calculates the number of points from a few
user parameters but there's no particular reason why you need to do it that way.
And to answer your question about polys vs triangles, there's not a lot of
difference since polys do get broken into rTriangles for rendering. The main
difference is that a poly can draw its outline rather than drawing all the
inner triangles, and it has some idea of its vertex interconnections.
-jonathan
On Apr 20, 2011, at 7:32 AM, Stephen Newbold wrote:
> Don't worry, I just answered my own question. It is just taking the last
> argument as 'true' and the previous 3 points are defining a 3-sided poly, or
> triangle. Man, long day! Still not sure what 'num_points' does as changing
> it seems to make little difference.
>
> Steve
>
>
> Stephen Newbold wrote:
>>
>> Having looked at the 'docs' again, am I right in saying that Polygon()
>> requires arguments for the points plus a boolean value for whether the poly
>> is open or closed? If I use this out.add_primitive(obj, new Polygon(0, 1,
>> 2, 3, true)) I get a closed poly, if I use this, out.add_primitive(obj, new
>> Polygon(0, 1, 2, 3, false)) I get an open poly. Makes sense. But if I
>> don't provide this final argument why do I get a triangle rather than it
>> defaulting to open/closed?
>>
>> Steve
>>
>>
>> Stephen Newbold wrote:
>>>
>>> Ok, so I quickly went over this and due to the pointers you gave me the
>>> Sphere.cpp makes more sense. So anyway, I've kind of got it working but
>>> there something weird that I need to run past you.
>>>
>>> If you look at the code below (which is essentially a butchered version of
>>> the Sphere.cpp stuff, it compiles fine but I get a triangle comprising of
>>> the first 3 points rather that a 4 sided polygon. If I change the add
>>> primitive line to out.add_primitive(obj, new Polygon(0, 1, 2, 3, 4)); I get
>>> the result I expect, a poly with its vertexes at the coords I define. But
>>> not sure why 5 values works and only put it in as a wild stab-in-the-dark!
>>>
>>> Any idea what's going on? Also, a bit lost about what 'num_points' is
>>> actually doing. Am I right to set this to 'n' for a a n-sided poly?
>>>
>>> Steve
>>>
>>>
>>>
>>> void create_geometry(Scene& scene, GeometryList& out)
>>> {
>>> int obj = 0;
>>>
>>> unsigned num_points = 4;
>>>
>>> if (rebuild(Mask_Primitives))
>>> {
>>> out.delete_objects();
>>> out.add_object(obj);
>>>
>>> out.add_primitive(obj, new Polygon(0, 1, 2, 3));
>>>
>>> set_rebuild(Mask_Points | Mask_Attributes);
>>> }
>>>
>>> if (rebuild(Mask_Points)) {
>>> // Generate points:
>>> PointList* points = out.writable_points(obj);
>>> points->resize(num_points);
>>>
>>>
>>> (*points)[0].set(0, 0, 0);
>>> (*points)[1].set(0, 10, 0);
>>> (*points)[2].set(6, 8, 0);
>>> (*points)[3].set(5, 2, 0);
>>>
>>> }
>>>
>>> }
>>>
>>> Stephen Newbold wrote:
>>>>
>>>> That's all useful stuff. Cheers guys. I'll give it a proper go as soon
>>>> as I get a few spare hours.
>>>>
>>>> Steve
>>>>
>>>>
>>>>
>>>> Jonathan Egstad wrote:
>>>>>
>>>>> Btw if you can't preset the primitive sufficiently ahead of time (I had
>>>>> this snag with a custom subd primitive) you can set the vertices variable
>>>>> in the GeoInfo directly but you'll need to hack the header to get access.
>>>>>
>>>>> -jonathan
>>>>>
>>>>> Sent from my iPhone
>>>>>
>>>>> On Apr 19, 2011, at 3:02 PM, Jonathan Egstad <jegs...@earthlink.net>
>>>>> wrote:
>>>>>
>>>>>
>>>>>> No, just make sure the primitive contains all vert entries - their
>>>>>> values don't matter, just the total number of them.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Sent from my iPhone
>>>>>>
>>>>>> On Apr 19, 2011, at 2:29 PM, Nhat Phong Tran
>>>>>> <nhatphong.t...@googlemail.com> wrote:
>>>>>>
>>>>>>
>>>>>>> Does that mean that all the PointList stuff and set(x,y,z) should
>>>>>>> happen before add_primitive()??
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ----------------------------------------------------------
>>>>>>> nhat phong tran
>>>>>>> dipl. digital artist (FH)
>>>>>>> computer graphics & visual effects
>>>>>>>
>>>>>>> m_us: +1 (310) 866-6871
>>>>>>> m_de: +49 (176) 24 26 34 27
>>>>>>> fax: +49 (321) 213 25 866
>>>>>>>
>>>>>>> santa monica, ca 90401
>>>>>>>
>>>>>>> sent via iPhone
>>>>>>> ----------------------------------------------------------
>>>>>>>
>>>>>>> On Apr 19, 2011, at 13:30, Jonathan Egstad <jegs...@earthlink.net>
>>>>>>> wrote:
>>>>>>>
>>>>>>>
>>>>>>>> One (of many) details that's not obvious is the accounting of vertices
>>>>>>>> inside the GeoInfo and its importance in maintaining any vertex
>>>>>>>> attribute arrays. If you add additional vertices to a primitive
>>>>>>>> *after* the primitive has already been added to the GeoInfo (via
>>>>>>>> GeoInfo::add_primitive()) then vertex attribute array sizes can get
>>>>>>>> out of sync possibly causing a crash.
>>>>>>>>
>>>>>>>> So until that's fixed make sure to completely build your primitive
>>>>>>>> first before adding it to the GeoInfo.
>>>>>>>>
>>>>>>>> -jonathan
>>>>>>>>
>>>>>>>>
>>>>>>>> On Apr 19, 2011, at 11:55 AM, Nhat Phong Tran wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>> Well first you need to add an object which holds your primitives (i.e.
>>>>>>>>> a polygon) to your output GeometryList. You can do this like this:
>>>>>>>>>
>>>>>>>>> out.addObject(yourObjectID);
>>>>>>>>>
>>>>>>>>> Now that you have an object created, you can add your primitives to
>>>>>>>>> it, in your case a polygon.
>>>>>>>>>
>>>>>>>>> out.add_primitive(obj, new Polygon(0, 1, 2, 3));
>>>>>>>>>
>>>>>>>>> So this allocates a polygon class and assigns points 0-3 to be its
>>>>>>>>> vertices. But this doesn't mean that the polygon's shape has been
>>>>>>>>> defined yet, because the points 0-3 have not a set position yet. To do
>>>>>>>>> this you create a pointer to the pointlist that contains the points of
>>>>>>>>> your object, then you need to resize the pointlist to fit all of your
>>>>>>>>> primitives points. Then you iterate through the points of the polygon
>>>>>>>>> of your interest and set the coordinates of each point.
>>>>>>>>>
>>>>>>>>> PointList* points = out.writable_points(yourObjectID);
>>>>>>>>> points->resize(num_points);
>>>>>>>>>
>>>>>>>>> for(unsigned int p=0; p<4; p++){
>>>>>>>>> (*points)[p].set(x_pos, y_pos, z_pos);
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> Hope this helps!
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Nhat
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> ----------------------------------------------------------
>>>>>>>>> nhat phong tran
>>>>>>>>> dipl. digital artist (FH)
>>>>>>>>> computer graphics & visual effects
>>>>>>>>>
>>>>>>>>> m_us: +1 (310) 866-6871
>>>>>>>>> m_de: +49 (176) 24 26 34 27
>>>>>>>>> fax: +49 (321) 213 25 866
>>>>>>>>>
>>>>>>>>> santa monica, ca 90401
>>>>>>>>>
>>>>>>>>> sent via iPhone
>>>>>>>>> ----------------------------------------------------------
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 19 April 2011 09:07, Stephen Newbold
>>>>>>>>> <stephe...@moving-picture.com> wrote:
>>>>>>>>>
>>>>>>>>>> Hi. Anybody know of any easy to understand documentation on how to
>>>>>>>>>> create
>>>>>>>>>> polygons using the NDK? I had a look through the Sphere.cpp example
>>>>>>>>>> that
>>>>>>>>>> ships with Nuke and like most things it went completely over my
>>>>>>>>>> head. I'm
>>>>>>>>>> hoping to be able to create something simple, just a four sided poly
>>>>>>>>>> defined
>>>>>>>>>> by 4 corner points, but have zero idea on how to go about it.
>>>>>>>>>>
>>>>>>>>>> Cheers,
>>>>>>>>>> Steve
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> Stephen Newbold
>>>>>>>>>> Senior Compositor - Film
>>>>>>>>>> MPC
>>>>>>>>>> 127 Wardour Street
>>>>>>>>>> Soho, London, W1F 0NL
>>>>>>>>>> Main - + 44 (0) 20 7434 3100
>>>>>>>>>> www.moving-picture.com
>>>>>>>>>>
>>>>>>>>>> _______________________________________________
>>>>>>>>>> Nuke-dev mailing list
>>>>>>>>>> Nuke-dev@support.thefoundry.co.uk
>>>>>>>>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> Nuke-dev mailing list
>>>>>>>>> Nuke-dev@support.thefoundry.co.uk
>>>>>>>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
>>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> Nuke-dev mailing list
>>>>>>>> Nuke-dev@support.thefoundry.co.uk
>>>>>>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
>>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
>>>>>>>
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>>>>>> Nuke-dev mailing list
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>>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>
>>>>
>>>> --
>>>> Stephen Newbold
>>>> Senior Compositor - Film
>>>> MPC
>>>> 127 Wardour Street
>>>> Soho, London, W1F 0NL
>>>> Main - + 44 (0) 20 7434 3100
>>>> www.moving-picture.com
>>>>
>>>>
>>>> _______________________________________________
>>>> Nuke-dev mailing list
>>>> Nuke-dev@support.thefoundry.co.uk
>>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
>>>>
>>>
>>>
>>> --
>>> Stephen Newbold
>>> Senior Compositor - Film
>>> MPC
>>> 127 Wardour Street
>>> Soho, London, W1F 0NL
>>> Main - + 44 (0) 20 7434 3100
>>> www.moving-picture.com
>>>
>>>
>>> _______________________________________________
>>> Nuke-dev mailing list
>>> Nuke-dev@support.thefoundry.co.uk
>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
>>>
>>
>>
>> --
>> Stephen Newbold
>> Senior Compositor - Film
>> MPC
>> 127 Wardour Street
>> Soho, London, W1F 0NL
>> Main - + 44 (0) 20 7434 3100
>> www.moving-picture.com
>>
>>
>> _______________________________________________
>> Nuke-dev mailing list
>> Nuke-dev@support.thefoundry.co.uk
>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
>>
>
>
> --
> Stephen Newbold
> Senior Compositor - Film
> MPC
> 127 Wardour Street
> Soho, London, W1F 0NL
> Main - + 44 (0) 20 7434 3100
> www.moving-picture.com
> _______________________________________________
> Nuke-dev mailing list
> Nuke-dev@support.thefoundry.co.uk
> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-dev
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