depthBias property
World-space offset toward the camera used for coplanar surface details. Positive values keep an overlay in front of its supporting surface without modifying its node transform. Zero and negative values leave the draw position unchanged. A fixed world offset provides fewer depth-buffer units as camera distance grows, so distant coplanar surfaces may need a larger value.
Implementation
// TODO(depth-bias-distance): add a distance or slope-scaled mode for decals
// that must remain separated across a large depth range.
double depthBias = 0.0;