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[Marvin Fröhlich]

Have you tried setting the light position before the viewing transformation (not in the transformation but so that the transformation occurs after the position of the light is declared)?

The view transformation is always pushed to opengl before all transformgroups are. So this won't work. Even if I have little of time this week, I will try to find some time to have a look at this.

Marvin

[Pandaemonium]

I don't know how to get this to work in Xith, but here is a snippet taken from the Red Book which I think is the overall goal:

Example 5-7 : Light Source That Moves with the Viewpoint

Code:

GLfloat light_position() = { 0.0, 0.0, 0.0, 1.0 };

glViewport(0, 0, (GLint) w, (GLint) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(40.0, (GLfloat) w/(GLfloat) h, 1.0, 100.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glLightfv(GL_LIGHT0, GL_POSITION, light_position);

If the viewpoint is now moved, the light will move along with it, maintaining (0, 0, 0) distance, relative to the eye. In the continuation of Example 5-7, which follows next, the global variables (ex, ey, ez) and (upx, upy, upz) control the position of the viewpoint and up vector. The display() routine that's called from the event loop to redraw the scene might be this:

Code:

static GLdouble ex, ey, ez, upx, upy, upz;

void display(void)
{
    glClear(GL_COLOR_BUFFER_MASK | GL_DEPTH_BUFFER_MASK);
    glPushMatrix();
        gluLookAt (ex, ey, ez, 0.0, 0.0, 0.0, upx, upy, upz);
        glutSolidTorus (0.275, 0.85, 8, 15);
    glPopMatrix();
    glFlush();
}

When the lit torus is redrawn, both the light position and the viewpoint are moved to the same location. As the values passed to gluLookAt() change and the eye moves, the object will never appear dark, because it is always being illuminated from the eye position. Even though you haven't respecified the light position, the light moves because the eye coordinate system has changed.

This method of moving the light can be very useful for simulating the illumination from a miner's hat. Another example would be carrying a candle or lantern. The light position specified by the call to glLightfv(GL_LIGHTi, GL_POSITION, position) would be the x, y, and z distance from the eye position to the illumination source. Then as the eye position moves, the light will remain the same relative distance away.

[Marvin Fröhlich]

I have created a View attached SpotLight testcase (org.xith3d.test.lighting.ViewSpotlightTest). Well, this testcase needs a better shading model like phong shading. But it still demonstrates, what you need.

I will later create a directly supported internal light-view-attachment. But not this week, I suppose.

Marvin

[hawkwind]

nice....thanx...let me play with it.

[Marvin Fröhlich]

Now the integrated solution is online and works. Have a look at the testcase. Yu can also attach a light to a Node in the scenegraph. Have a look at SphereMotionLightingTest for an example.

Marvin