[osg-users] Draw vertex as Circle with color given by some Vec4 array

[Bruno Oliveira]

Hi Nick,
thanks for your answer. I read the osgvertexattributes.cpp example and did
not quite get it at first. Do you know if there are any further
documentation or snippets I could read?

Or maybe if you have quick snippets it could spare me some valuable time.

2017-01-02 20:56 GMT+00:00 Trajce Nikolov NICK <
trajce.nikolov.nick at gmail.com>:

> Hi Bruno,
>
> yes, you can pass VertexAttributes to the program and look them up in the
> shader. You can pass the centers as Vec3Array, Vec4Array for colors and
> probably encode the radius into float array or the vertex.w() from the
> vertex array.
>
> Do a search through the examples for how to set up your program with
> VertexAttributes ... Ping me if you if troubles, I might be able to give
> some snippets
>
> Cheers,
> Nick
>
> On Mon, Jan 2, 2017 at 8:21 PM, Bruno Oliveira <
> bruno.manata.oliveira at gmail.com> wrote:
>
>> Hello,
>>
>>
>> I have an array of 3d points that I want to render in a scene. I want to
>> render them as circles, centered on each point coordinates, with a given
>> radius and a color that is given by a color array I have in memory.
>>
>> For now, I am creating a node for each point, that consists of a
>> PrimitiveSet (polygon) that I iterate around the point center. (Check code
>> below).
>>
>>
>> Now I know this can be done with Shaders. I can draw the circle directly
>> in the fragment shader with this example (http://www.geeks3d.com/201307
>> 05/shader-library-circle-disc-fake-sphere-in-glsl-opengl-glslhacker/).
>>
>> But I need to pass the vertex centers and respective colors. Is it
>> possible to pass a osg::Vec3Array* with vertex centers and a
>> osg::Vec4Array* of colors directly to a Shader, so that I can , in a single
>> compiled Shader program, handle all point positions and colors?
>>
>> Here is teh code for drawing the circle, I use this for each vertex:
>>
>> osg::Vec3Array* getArray(const float radius, const int points, const
>> osg::Vec3& center) {
>>     auto array = new osg::Vec3Array();
>>     const float ratio = (float(2.0*osg::PI) / float(points));
>>     for (int i = 0; i < points; i++) {
>>         const float angle = float(i) * ratio;
>>         array->push_back(osg::Vec3(
>>                     center.x() + radius*cosf( angle ),
>>                     center.y() + radius*sinf( angle ),
>>                     center.z())
>>                 );
>>     }
>>     return array;
>> }
>>
>> osg::Geometry* getGeometry(const float radius, const int points, const
>> osg::Vec3& center) {
>>     osg::Geometry* geom = new osg::Geometry();
>>
>>     geom->setVertexArray(getArray(radius, points, center));
>>     geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::POLYGON,
>> 0, points));
>>
>>     return geom;
>> }
>>
>>
>> _______________________________________________
>> osg-users mailing list
>> osg-users at lists.openscenegraph.org
>> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>>
>>
>
>
> --
> trajce nikolov nick
>
> _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openscenegraph.org/pipermail/osg-users-openscenegraph.org/attachments/20170102/7f52bf20/attachment-0003.htm>