[osg-users] [Problem with osgLight]
Paul Melis
paul at science.uva.nl
Wed Jun 18 08:39:48 PDT 2008
Jean-Baptiste Authesserre wrote:
> 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...
You can check the .osg file exported by Blender to see if the normals
are set correctly. There shouldn't be that many for this simple model I
suspect.
Paul
>
> 2008/6/18 Paul Melis <paul at science.uva.nl <mailto: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> <mailto: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>
> <mailto: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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