On 7/11/2023 4:08 PM, Trevor Orr via Discuss wrote:

Why?  What went wrong?

I believe that without --render it should give you the same image that
you would have gotten from an F5 preview in the UI.  Do those look OK?

If there are transparent patches in your preview results, it suggests
that you need to set "convexity" somewhere in your model.  See this FAQ
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/FAQ#Why_are_some_parts_(e.g._holes)_of_the_model_not_rendered_correctly?.

I have not seen the convexity parameter before, I will play around with
that and see if that fixes my preview issues

On July 11, 2023 6:43:27 PM Jordan Brown openscad@jordan.maileater.net wrote:

On Wed, Jul 12, 2023 at 01:43:11AM +0000, Jordan Brown wrote:

Or the camera position is inside some "subtracted" object.

Try
difference () {
cylinder (d=30, h=40, center=true);
translate ([0,-100,0]) cube (100);
}

(in my example, it looks as if the subtract didn't work. It's the
easiest example I could think of where F5-preview and F6-render differ
significantly. But other failure modes also exist. If you're dragging
the controls, it is reasonably easy to find a viewpoint where you can
see what you are doing, but that's no good if you're animating some
mechanism for a video).

Roger. 

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