I didn't find out I was an aphant until after I'd finished my PhD in robotics. It was a big shock to realize that when all of my peers were saying things like "imagine it moves this way" or "visualize the motion, " they could see something moving in 3D in their heads. I had always just thought about the angles, the equations, and the other analytical properties of the robot or system, not a movie playing in my head. When there are things that seem to necessitate visualization (in physics or otherwise), I turn to my always-on-hand notebook, mini-whiteboard, Boogie board, or whatever else I've got and sketch it. I think one of the reasons that I sketch so much, and learned how to build 3D computer graphics, was to compensate (albeit subconsciously at the time) for my lack of in-head visualization capabilities. 

I personally excel at geometry, I think because it is abstract, but am really bad with mechanical and spatial comprehension.  I comprehend it well when I see it, but I can't just describe it without physically visualizing it.  I've never gone deep into math though.  Not my forte, but I am not sure if that would be any different if I could internally visualize.

I'll preface this by saying that I'm not studying in physics, but in finance. I like to think that I have good spatial reasoning skills but I've never taken any kind of test to confirm it, aside from highschool physics courses.   If I'm doing this for a test about spatial reasoning questions, I tend to approach the question methodically. I'll find specific sections of the test image that are relevant to the answer and try to rotate or move them in accordance to the question. I can't do this in my head, so I tend to move my eyes across the test sheet to help me "visualize" the answer. In other words, I've I'm trying to "visualize" a square, I'll move my eyes across the paper in the shape of a square. I'm not sure of the mechanism behind it, but it seem to help me. A lone square is probably a bad example, but this only really works with 2D shapes. If I'm doing something with 3D shapes, I'll compress them down to 2D and do the same thing. If that's not possible, I would probably draw something in the margins to help me understand how two or more 3D objects interact with each other. Drawing something in the air also seems to help, even though it makes me look like a crazy person. Really, just use all the tool at your disposal, draw something in the margins, in the air, move your hands, etc. Anything that can help you is fair game.  I'm not sure if this will be helpful to you, but it works for me, so it can't hurt to give it a try. 

I have a BS in Physics. Some 5 decades later I now know why I ran out of steam. My mathematics were the limiting factor; I couldn't get the hang of matrix transformations, literally a block. I had a good memory so was good at descriptive and experimental stuff which got me through.   Thankfully I turned down an offer of a PhD in astronomy... .

I did well in math and science in high school except for trig. In college I majored in physics for a couple of years, dropped optics twice, then changed my major to psych and completed a Ph.D..

Yes,can’t do anything with 3D vision,physics was my worst subject in school,could never visualise a thing

I have lived with this condition all my life. Thinking others were making things up, when they said, "Picture this...". I would simply put it in analogy format, this would make it easier to not only comprehend but to others understand where I came from. The sciences were actually my stronger subjects throughout my academic time.  

The best way I’ve been able to overcome this is by finding as many illustrations and artist renditions on topics of the matter at hand. If I’m able to recall facts from the imagery, while not able to recall the imagery itself, it gives me some form of information to use. Sadly what works for some may not work for others, as we’re still discovering things about our brains as time is unfolding around us. Through effort you may discover a completely unique way of doing it that no other brain has thought of before.

Yes. That's what aphantasia is.

I didn't find out I was an aphant until after I'd finished my PhD in robotics. It was a big shock to realize that when all of my peers were saying things like "imagine it moves this way" or "visualize the motion, " they could see something moving in 3D in their heads. I had always just thought about the angles, the equations, and the other analytical properties of the robot or system, not a movie playing in my head. When there are things that seem to necessitate visualization (in physics or otherwise), I turn to my always-on-hand notebook, mini-whiteboard, Boogie board, or whatever else I've got and sketch it. I think one of the reasons that I sketch so much, and learned how to build 3D computer graphics, was to compensate (albeit subconsciously at the time) for my lack of in-head visualization capabilities. 

I personally excel at geometry, I think because it is abstract, but am really bad with mechanical and spatial comprehension.  I comprehend it well when I see it, but I can't just describe it without physically visualizing it.  I've never gone deep into math though.  Not my forte, but I am not sure if that would be any different if I could internally visualize.

I'll preface this by saying that I'm not studying in physics, but in finance. I like to think that I have good spatial reasoning skills but I've never taken any kind of test to confirm it, aside from highschool physics courses.   If I'm doing this for a test about spatial reasoning questions, I tend to approach the question methodically. I'll find specific sections of the test image that are relevant to the answer and try to rotate or move them in accordance to the question. I can't do this in my head, so I tend to move my eyes across the test sheet to help me "visualize" the answer. In other words, I've I'm trying to "visualize" a square, I'll move my eyes across the paper in the shape of a square. I'm not sure of the mechanism behind it, but it seem to help me. A lone square is probably a bad example, but this only really works with 2D shapes. If I'm doing something with 3D shapes, I'll compress them down to 2D and do the same thing. If that's not possible, I would probably draw something in the margins to help me understand how two or more 3D objects interact with each other. Drawing something in the air also seems to help, even though it makes me look like a crazy person. Really, just use all the tool at your disposal, draw something in the margins, in the air, move your hands, etc. Anything that can help you is fair game.  I'm not sure if this will be helpful to you, but it works for me, so it can't hurt to give it a try. 

I have a BS in Physics. Some 5 decades later I now know why I ran out of steam. My mathematics were the limiting factor; I couldn't get the hang of matrix transformations, literally a block. I had a good memory so was good at descriptive and experimental stuff which got me through.   Thankfully I turned down an offer of a PhD in astronomy... .

I did well in math and science in high school except for trig. In college I majored in physics for a couple of years, dropped optics twice, then changed my major to psych and completed a Ph.D..

Yes,can’t do anything with 3D vision,physics was my worst subject in school,could never visualise a thing

I have lived with this condition all my life. Thinking others were making things up, when they said, "Picture this...". I would simply put it in analogy format, this would make it easier to not only comprehend but to others understand where I came from. The sciences were actually my stronger subjects throughout my academic time.  

The best way I’ve been able to overcome this is by finding as many illustrations and artist renditions on topics of the matter at hand. If I’m able to recall facts from the imagery, while not able to recall the imagery itself, it gives me some form of information to use. Sadly what works for some may not work for others, as we’re still discovering things about our brains as time is unfolding around us. Through effort you may discover a completely unique way of doing it that no other brain has thought of before.

Yes. That's what aphantasia is.