Why can't I rub the spotlight texture on my sphere after pressing the Z button?

[system]

Hi all:)
I have just started learning zbrush and currently I m trying to texture eyeballs by using the spotlight feature.
I have looked into a number of tutorials on how to use the function.

I cannot paint my texture onto the eyeball after switching from light box to paint function by pressing Z.
It just show me the followings but I could not rub the texture onto my eyeball.

small_orange_diamondWould anyone please help me? Thanks!!

Attachments

[marcus_civis]

Make sure that in the Brush palette, Samples sub-palette, the Spotlight Projection button is on. Also, try with RGB Intensity set to 100. I’m assuming you don’t have a texture map applied to the model in the Tool>Texture Map sub-palette.

[Doug_Jones]

12k points isn’t enough, it’s probably not enough for one eyeball, subdivision will be necessary.(more points to hold the information)
Cheers