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I have a problem rendering a sphere with a semi-transparent material on a transparent background. When rendered in preview mode, the result is correct, the invisible parts of the sphere don't show up :

Preview Render

But when I calculate the final render, I only get a totally transparent image.

When the transparency box in the Render Properties is unchecked, it works fine : the problem only occurs when the background transparency is enabled.

For the material, I used a noise texture linked to an emission shader which I added to a transparent one :

Preview Render

Would you have any idea where it comes from ?

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  • $\begingroup$ If you can see your material in the viewport, but not on the rendered image, you are probably experiencing a limitation of the rendered image's viewport. It has a problem displaying semi transparent emissive pixesl with no occlusion. Read: blender.stackexchange.com/questions/57816/… Check your image using the RGB view, not the RGBA view. Chances are your material is correct but the viewer cannot display it. $\endgroup$ – cegaton Jan 21 '17 at 16:51
  • $\begingroup$ Probably related: blender.stackexchange.com/questions/56950/… $\endgroup$ – cegaton Jan 21 '17 at 16:54
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Your problem is that you are adding the shaders instead of mixing them. Therefore, the material is interpreted by Cycles as being 100% transparent, regardless of what else it is.

You can fix this by swapping out your Add Shader for a Mix Shader and plugging in your texture to the Fac value instead of the Strength of the Emission node.

enter image description here

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