To spawn on a bitmap:
Use a Position Object operator and set the density to be controlled by texmap...drag in your map and it should work
Gradient ascent/trace won't work with pure blacks/whites. It's basically forming a UV-space vector by examining color value differences in a small sampling of texture points. Imagine your bitmap used as a displacement map on a mesh...the gradient modes are basically trying to find the direction of a slope created by your bitmap. Pure black/white areas have no slope and thus won't return a meaningful vector.
Use a Position Object operator and set the density to be controlled by texmap...drag in your map and it should work
Gradient ascent/trace won't work with pure blacks/whites. It's basically forming a UV-space vector by examining color value differences in a small sampling of texture points. Imagine your bitmap used as a displacement map on a mesh...the gradient modes are basically trying to find the direction of a slope created by your bitmap. Pure black/white areas have no slope and thus won't return a meaningful vector.