Recently-developed models of decision behavior have provided richer accounts of the cognitive processes underlying choice by examining performance on tasks where responses can fall along a continuum, such as identifying the color or orientation of a stimulus. While these have laudably expanded models beyond simple binary and multi-alternative choice paradigms, critical concerns remain about the models' lack of completeness, poor computational tractability, or inability to capture important characteristics of choice responses. Specifically, no model is yet able to predict a truly continuous distribution of responses that exhibit multimodality, where responses have more than one central tendency. This property appears frequently in real data where there is conflict between decision information favoring responses at different locations, such as a predecision cue that indicates a different response than the stimulus. These patterns of data are informative to psychological theory, making it critical to develop a better account of continuous response tasks. In this theoretical note, we use a geometric approach developed by Kvam (2019) to provide a solution to this issue and to reconcile the different existing models under a common framework. The resulting geometric diffusion model (GDM) yields a truly continuous joint distribution of responses and response times, produces multimodal distributions of responses, and offers much greater computational efficiency than models producing discrete approximations of continuous responses. We demonstrate that this model can be extended to account for behavior when alternatives are not arranged in a circle, including a case where responses can fall along a 2-dimensional plane such as identifying the location of an item on a computer screen.