Background (may be safely ignored): I am buying (most of) a rowhouse from the 1930s. I am now working with an architect to improve its energy efficiency.
Let us focus on the main room, which can be said to be a long box pointing East-northeast, with two tall SWS-facing windows. I would like to be able to depict where direct light will fall through the windows at a given time on a given day.
This doesn't seem hard to do in Python (or what have you) - just some solid geometry - but I would not want to reinvent the wheel. On the other hand, I've wasted the last 90 minutes of my life with Velux Daylight Visualizer (which a friend pointed out to me), only to conclude that it is not designed to do what I want it to do. So: what sort of software (preferably free) can I use for this sort of thing?
(You can guess the idea - place surfaces that absorb radiant heat (and release it slowly) at places that have direct sun exposure during the winter; I suppose we will try to block some direct sunlight during the summer.)
PS. My apologies if this is the wrong forum for this question. What forum would be better?
EDIT: expressing the azimuth and elevation in terms of the date and solar day is standard (see Duffin-Beckmann for a simple model you can come up with yourself). I would like to see an animation. Not rocket science, but it's unclear to me how to do it using RADIANCE (which at the same time is ridiculous overkill).
UPDATE: I went and did the animation myself in Python/SageMath, using the pysolar library to compute azimuth and elevation, and Three.js for 3D animations that can be turned around. It was a two-day task. Here is a still frame: 
