Draw Vector in viewpoint lookat direction

[Chrissy2009]

Hi,

I want to draw a line from one object in a special direction for a given amount.

The amount (or the length) is from a slider and that works fine!

But the direction of the line should be the viewpoint lookat direction.

So for example my viewpoint is behind of a ball and now I want to draw a line to see how the ball will roll.

I use:

current = balls[0].get(viz.POSITION)
vector = balls[0].get(viz.LOOK)
future = vizmat.MoveAlongVector(current, vector, slider.get()*2)
hit = viz.intersect(current, future)
viz.startlayer(viz.LINE_LOOP)
viz.vertexcolor(viz.RED)
viz.linewidth(3)
viz.vertex(current)
viz.vertex(future)
rod = viz.endlayer()

But this doesn't work. :-(

Can anybody help me?

And additionally it would be very great if the vector will be changed depending on a change of the viewpoint. If I turn the viewpoint left or right, the vector will be drawn in the corresponding direction.

[Gladsomebeast]

Set the parent of the rod to the ball so that it appears on the ball. Now it is at the origin of the world.

You can do the calculation again and set the position of the second vertex every time the view moves if you like.

[Gladsomebeast]

Actually, don't set the parent of the rod to the ball. That won't fix things. I was wrong.