For interactive rendering in medical imaging, physically-based volume rendering of a volume of a patient may better assist physicians in diagnosis, prognosis, and/or planning. To provide for more rapid interaction, direct volume rendering is used during interaction. The rendering then transitions to physically-based rendering when there is no interaction. For smoothing the transition and/or preserving cohesive perceptual details, images from the different types of rendering may be blended in the transition and/or during interaction.