[osg-users] how do I make the light always hit the front of the camera?

newli...@gmail.com newlife958 at gmail.com
Tue Mar 9 16:23:30 PST 2021

Hi, Robert .
First of all, thank you for your interest and answer.

I'm rendering using osg::Light and osg::LightSource with a spotlight 
pointing down.

The exact position is set using light->setPosition()

The direction of the light is set with the code below.

     osg::vec3d world =world + osg::Vec3d(0.0, 0.0, -0.6)

However, if the camera's heading is rotated in the current implementation, 
the light currently being rendered in front is stopped at the position and 
only the camera rotates.

I want to rotate the position of the light along with the heading of the 
However, if you adjust the Direction value to rotate the position of the 
light, the rendered position will be distorted without rotating as desired.

So, I tried various things using the code below, but I didn't get the 
desired result.

osg::PositionAttitudeTransform *_pat = new osg::PositionAttitudeTransform();
osg::Quat ori =  osg::Quat(osg::DegreesToRadians(0.0), osg::Vec3(0, 1, 0)) *
osg::Vec3(1, 0, 0)) *
osg::Vec3(0, 0, 1));

Is there a good way to adjust the position of the light like a camera?

2021년 3월 9일 화요일 오후 5시 12분 42초 UTC+9에 robert.... at gmail.com님이 작성:

> Hi ?
> You don't say how you are rendering your present lights so providing 
> guidance on how to adjust it isn't possible, you'll need to provide more 
> information about your render system and what it relies upon for 
> controlling the position and direction of the light.
> Also it's hard to understand what you mean.  Rotating something by 360 
> degrees takes it full circle and back to where it was originally - so this 
> bit makes no sense whatsoever.
> The light in the scene looks to be a spot light pointing downwards, 
> pointing that back towards the camera would be a 90 degree rotation, but 
> pointing a spotlight at the camera would be pretty odd.  Could you mean 
> something completely different from what you are saying?
> Robert.

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