Here's a Blender video on creating a gradient, and halfway through (at 3 minutes) it shows sharp lines. I could follow it with the Texture Coordinate, Mapping, and Separate XYZ nodes, but when it got to the color ramp node, I couldn't follow (translate to Poser Cycles), but maybe you can.

https://www.youtube.com/watch?v=ViqfL0LOwUM

---

W11,Intel i9-14900KF @ 3.20GHz, 64.0 GB RAM, 64-bit, GeForce GTX 4070 Ti SUPER, 16GB. 

Old lady hobbyist.

All visual art or fiction is "playing with dolls."