I have modeled a leopard frog with the mirror modifier and unwrapped it, and am attempting to paint the diffuse texture in the 3D viewport. When using the draw brush, painting works fine. When using the fill brush without a gradient, it works as expected.
My problem occurs when I try to use the radial gradient option on the fill brush to paint the spots of the frog. The results are mostly crap. For example, I'll paint the top of the body, and it paints a spot on the bottom as well. Or I'll paint on the side of the body and the spot shows up on the belly instead. Sometimes, the brush won't even work and I have to fiddle with re-unwrapping and making a new image to paint on to get it to work again. I feel confident the problem is not my UV map; I have islands for the legs, body, inner mouth, hands, etc. No vertices are overlapping in the UV editor. When I texture paint from the UV window, I get no unexpected results. For some reason the fill brush just completely craps out on me when I use a radial gradient in the viewport.
I should add that I've tried toggling Occlude, Cull and Normal options in the toolbar to no effect.