Gradient Perception in Color-Coded Scalar Fields

Color mapping is a commonly used technique for visualizing scalar fields. While there exists advice for choosing effective colormaps, it is unclear if current guidelines apply equally across task types. We study the perception of gradients and evaluate the effectiveness of three colormaps at depicting gradient magnitudes. In a crowd- sourced experiment, we determine the just-noticeable differences (JNDs) at which participants can reliably compare and judge variations in gradient between two scalar fields. We find that participants exhibited lower JNDs with a diverging (cool-warm) or a spectral (rainbow) scheme, as compared with a monotonic-luminance colormap (viridis). The results support a hypothesis that apparent discontinuities in the color ramp may help viewers discern subtle structural differences in gradient. We discuss these findings and highlight future research directions for colormap evaluation.

颜色映射是可视化标量场的一种常用技术。尽管存在关于选择有效颜色映射的建议，但当前指南是否适用于所有任务类型尚不明确。本研究探讨了梯度感知并评估了三种颜色映射在描绘梯度幅度方面的有效性。在一场众包实验中，我们确定了参与者能够可靠地比较和判断两个标量场之间梯度变化的最低可察觉差异（JNDs）。我们发现，与单调亮度颜色映射（viridis）相比，参与者在使用发散（冷-暖）或光谱（彩虹）方案时表现出更低的JNDs。这些结果支持了一个假设，即颜色渐变中的明显不连续性可能有助于观众辨识梯度中的细微结构差异。我们讨论了这些发现，并突出了颜色映射评估的未来研究方向。