[osg-users] Combine geodes

Robert Osfield robert.osfield at gmail.com
Fri Jan 15 06:13:54 PST 2016

Hi Artem,

The osgreflect example is rather basic and very old so doesn't
illustrate the clear mask (it's one of our very first example

The osg::Camera has support for controlling the OpenGL clearing,  from
include/osg/Camera header:

       /** Set the clear mask used in glClear().
          * Defaults to GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT. */
        inline void setClearMask(GLbitfield mask) { _clearMask = mask;
applyMaskAction(CLEAR_MASK); }

        /** Get the clear mask.*/
        inline GLbitfield getClearMask() const { return _clearMask; }

The way you'd use in the context of stencilling would be to set up
either the master camera to clear the stencil buffer, or use a
multi-pass approach with osg::Camera embedded in the scene graph to
create multiple render stages each with their own clear - the osghud
example illustrates this.  Alternatively you use viewer slave Camera
to do multi-pass, again the osghud example illustrates this.


On 15 January 2016 at 12:20, Artem Ivanov <tema.krukovets at gmail.com> wrote:
> Actually, I have some more questions about using stencil buffer:
> - how can I clear stencil buffer on render bin? (in OpenGL tutorials everyone uses glClear(GL_STENCIL_BUFFER_BIT)
> - is it possible to disable stencil buffer at the begining of the render bin and enable it at the end? Or should I disable usage of the stencil buffer on previous render bin and enable it on next?
> robertosfield wrote:
>> On 13 January 2016 at 18:49, Artem Ivanov <> wrote:
>> > Thanks for your responses.
>> > Actually, I want only visual effect (like union operation on two geometries), so I think it is about pure rendering.
>> > It would be great if you can describe this method or provide some information about it.
>> >
>> To understand the ideas behind managing the rendering It would
>> probably be easiest to just read up online one how to do such
>> rendering using OpenGL.  Topics to look into would be OpenGL, Stencil
>> Buffer Consutrctive Solid Geometry.
>> Perhaps members of the community have their favourite tutorials on this topic.
>> The OSG fully supports stencilling, controls on depth+color buffers,
>> shaders, controls for managing multi-pass rendering.  The osgreflect
>> example provide a very simple example of managing stencilling.
>> Robert
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