[osg-users] [Problem with osgLight]

[Jean-Baptiste Authesserre]

This is the result when I remove the helmet. I really don(t understand. The
square is obtained thanks to the following way. I ceated a cube with blender
3*3*0.1 (small depth along th Z-axis)
I load on that cube a texture. I attach to this mail the result without the
helmet and the texture attached to the cube.
It's very strange...

2008/6/18 Paul Melis <paul at science.uva.nl>:

> Jean-Baptiste Authesserre wrote:
>
>> Sorry for the previous mail. I'm a little confused. My camera is
>> configured to take Y-axis as UP axis. In my 3D-model, I put the helmet so
>> that the bottom of the helmet correspond to negative Y, and the top to
>> positive Y (cf attached figure). The camera look at (0, 0, 0). Thus I can
>> obtain the attached image. To enlight the scene I put the light at 0 on
>> X-axis so the region around the bottom corners of the square be enlighten
>> the same way (the square is in the XY plane). However the region around
>> bottom-left corner is darker than the region around bottom-right corner.
>> What have I missed?
>>
> Ah! You said "my object isn't uniformly enlighten" in your original mail.
> With "object" I figured you meant the whole thing/"helmet". I now see what
> you mean w.r.t. the dark corner on the square. Could it be that you have an
> incorrect normal for that corner of the square? Are the square and helmet
> one object? Does it still show when you display only the square (i.e. could
> it be an artifact that actually comes from the helmet, and not the square)?
>
> Paul
>
>>
>> Jean-Baptiste
>>
>> 2008/6/18 Jean-Baptiste Authesserre <authesse at gmail.com <mailto:
>> authesse at gmail.com>>:
>>
>>    Hi,
>>
>>    I am a little confused. My camera
>>
>>    2008/6/18 Paul Melis <paul at science.uva.nl
>>    <mailto:paul at science.uva.nl>>:
>>
>>
>>        Jean-Baptiste Authesserre wrote:
>>
>>            Hi everyone,
>>
>>            I have some problem with OSG Light, and I don't find
>>            answer in the osg archives. My problem is the following :
>>            I don't understand why with the following code my object
>>            isn't uniformly enlighten. (cf. image in attached document)
>>            -The black and white square of the image is centered at
>>            (0, 0, 0) (in world frame with convention (x, y, z))
>>            -The camera is located at (0, 0, -20)
>>            -the light is located at (0,20, -15)
>>
>>        If you didn't change this yourself then +Z will be the up
>>        axis, btw
>>
>>
>>
>>            The code for activating light is the following:
>>
>>            /*****************************
>>            ** light *************************************/
>>
>>
>>               //Creation of light source
>>               osg::Light* light = new osg::Light();
>>               osg::LightSource * lightsource = new osg::LightSource();
>>               lightsource->setLight(light);
>>               // put the light source in the scenegraph
>>               root->addChild(lightsource);
>>
>>               // turn light on
>>               osg::StateSet * stateset = root->getOrCreateStateSet();
>>               lightsource->setStateSetModes(*stateset,
>>            osg::StateAttribute::ON);
>>               light->setAmbient(osg::Vec4d(1.0, 1.0, 1.0, 1.0));
>>               //light->setDiffuse(osg::Vec4d(0.0, 0.0, 0.0, 0.0));
>>               //light->setSpecular(osg::Vec4d(1.0, 1.0, 1.0, 1.0));
>>               light->setPosition(osg::Vec4d(0.0, 20.0, -15.0, 1.0));
>>
>>
>>  /******************************************************************************/
>>
>>            So, I don't understand why the bottom-left corner of my
>>            square is darker than the others corners
>>
>>        I don't see any difference here between left and right bottom
>>        corners, they're equally dark IMHO. Which seems to make sense,
>>        as you've put the light source above and little in front of
>>        the camera, but in the center of the object (the X plane).
>>
>>        Paul
>>
>>            Has anybody an Idea?
>>
>>
>>            Best regards,
>>
>>            Jean-Baptiste.
>>
>>  ------------------------------------------------------------------------
>>
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