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I've been working on a Blender model (using Blender 2.79, but I've also tested in 2.91.2 and got the same result) with the goal of producing a realistic shadow image for an airplane from any angle. I'm using Cycles render engine, have imported my airplane model, and have a ground plane marked as a shadow catcher. I'm also using a Sun lamp with size 0 because I want crisp shadow edges. My lamp and camera need to be at the exact same location to generate the kind of shadow image I'm looking for.

My issue is that when I try to generate a shadow from a low elevation/grazing angle (around 30 degrees) I expect to see a long, stretched-out shadow on my shadow catcher. However, in reality I only see the shadow in places directly blocked by the airplane, meaning if I layer the outline of the airplane over the shadow image they are identical.

Does anyone know of settings I can change to get more realistic looking shadows?

Thank you so much for any help!

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    $\begingroup$ I do not understand the scene exactly. If the camera and the sun are at the same angle, and the sun is set up so that the shadow will be perfectly crisp, no shadow will be visible. This is entirely realistic, except that the camera leaves no shadow on the airplane. PS: The location of sun lamps has absolutely no effect on their lighting. $\endgroup$
    – TheLabCat
    Mar 1, 2021 at 5:00
  • $\begingroup$ The question is fairly well explained but screenshots would go a long way for people like me. $\endgroup$
    – Allen Simpson
    Mar 1, 2021 at 6:27
  • $\begingroup$ @ZargulTheWizard, I'm looking for something like a long, afternoon shadow to stretch out behind the image of the airplane. I do see what you're saying about how a shadow with perfectly crisp edges is going to be directly behind the object and not visible. Since the airplane is raised above the ground, I expected to be able to see the shadow stretched out behind it under the wings in the background? Or see the shadow extending out behind the wheels on the ground? Or is that still something I won't see unless the camera and lamp are at different angles? $\endgroup$
    – karis
    Mar 1, 2021 at 16:12
  • $\begingroup$ Well, I’m not sure, since I haven’t quite got the full scene in my head. 😋 but just to run over the physics of sun lamps: no matter what position a sunlamp is in, it will be treated as if it is an infinitely large flat light surface an infinite distance away. Only the angle of the sun lamp will be taken into account. If you can, share your blend file or a simplified version of it for reference. $\endgroup$
    – TheLabCat
    Mar 1, 2021 at 16:21
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    $\begingroup$ @ZargulTheWizard, your comment about the camera and sun being at the same angle sparked some thoughts so we changed the configuration of the file and solved the issue! Thank you so much! $\endgroup$
    – karis
    Mar 2, 2021 at 17:28

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Answering the question from ZargulTheWizard's comments - since the sun lamp and camera were in the same location, no shadow with perfectly crisp edges would be visible to the camera. To get the shadow images from the specific angle like I wanted, I left the lamp at the specific angle to create the shadow and then moved the camera directly overhead (0, 0, height) the object to capture the "stretched out" shadow effect.

Again thank you so much everyone for your help!

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