# Lesson goal: 3d graphics the depth

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In the last lesson you saw how to draw spheres using three dimemsional coordinates. In this lesson, we wanted to be sure you understand the z-coordinate, and how it give you the added element of "depth" in your graphics.

Let's again use scene3d() and sphere() to draw, but let's move a single sphere up and down along the z-axis.

Try these two tests:

Test #1: Start by drawing a sphere at (0,0,80) with a radius of 5. Then change the 80 to -80, as in (0,0,-80). What do you notice?

Test #2: Try drawing two spheres, like this:

1. Draw a sphere at (0,0,50) with a radius of 10 in a red color (ff0000).
2. Keeping the code in place for that sphere, draw another sphere at (10,0,30) with a radius of 10, in a green color (00ff00).
What do you see? Do you see the "depth" that 3D graphics offers?

# Now you try. Try running through these two tests, so you can see the depth and perspective given by 3d graphics.

Type your code here:

See your results here:

And remember, you are programming now. You can place lots of spheres using a for-loop like this:

scene3d() c = 0 for z=80,-80,-15 do if c % 2 == 0 then color = "ff0000" else color = "00ff00" end sphere(c*10,0,z,5,color) c=c+1 end Dismiss.

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