I am working on a render of Saturn as part of a scale model of the solar system, and have run into a problem with the transparency of the rings. I am using an alpha-mapped png image which seems to work fine, except for the break in Saturn's horizon, where it is crossed by the rings. (See image) It looks like refraction, which I certainly don't want in this case. How would I get rid of that?

Ring Material Node Layout Crappy Render

Or, since this is a scale model where 1BU = 10,000km, could this be a precision error miscalculating the re-transmission angle? The scene is lit with a Sun model, 143,350 BU away...

EDIT: Upon further research, this aberration is directly linked to the distance from the origin. I built a test scene to try to reproduce the problem, and was successful. The test rig is an emission plane over a striped sphere that is intersected by a fully transparent horizontal plane just above the equator. The brick floor is just a backdrop, and is not as severely distorted. enter image description here

At the origin, the render is clean: enter image description here

Moving the whole rig over to x = 5000, the distortion is clearly visible: enter image description here

And at x = 100,000, it becomes extreme! enter image description here

My guess is that this is a precision error from trying to calculate the exact angle of re-transmission through the clear plane with such high-magnitude inputs.

I tried just scaling everything down, but the distortion remains the same size relative to the geometry. Is this simply a practical limitation of the software that I should learn to live with, or might there be some way to get around it?


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.