Flamingo nXt

easy rendering for Rhino in Windows



When I render an image with a reflective ground plane, but having alpha enabled under the control panel/ environment tab so that the exported image has the transparent background I lose the relfection of the model, but maintain the surrounding shadows on the ground plane caused by the model?

Can somebody tell me what I am doing wrong ?


Thank you.

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The Alpha groundplane will only capture shadow.  The reflection will not be captured.


As a wrok around i would use photoshop and mirror the image and layer it behind the oreigianl rendering.  With a gradient mask it will look like a reflection.



Thanks Scott

I will give it a try in GIMP.


I found a more effective way as I could not get the mirror to work as the reflection originated along an oblique angle.

I made two renderings with the same viewpoint and setting. One with alpha enabled on the reflective ground plane, and one without.

Then in nXtImageEditor I saved the alpha channel mask from the one having the alpha data.

In Gimp I applied the alpha channel as a transparency mask to the reflection image. I tweaked the mask a little with the airbrush to ensure the whole reflection was visible.  

Max - Thanks for asking the question, you saved me a lot of time and frustration.  I am just learning and I want a reflection of the machine I am rendering in a 3/4 view. Because I can't do this easily in Photoshop, I was really looking forward to producing a nice reflection in Rhino/ Flamingo.

Hi Martha


I have found an even quicker approach :-)

Just one rendering with the reflective ground plane of your choice, and alpha disabled.

Save it as a .nXtImage and a .png 

Then in nXtImageEditor export the material mask to a .png

In GIMP open the  rendered image.png

Add a layer mask which is the greyscale image of itself

then add the exported material mask to a new layer

in material mask flood all the materials to a single colour, white, and background to black.

use this to get a "by colour selection of all the material"

then while editing the layer mask flood the associated material area with white (selection remains active through layers, just select the right one, and hide others)

then use airbrush to brighten the shadow and reflection areas to a smooth transition to black

then apply the mask, and delete all other layers.

then export to png. 


On this subject my problem is the reverse in a sense:

Is there a way to exclude the ground plane from the scene via alpha channel but keep its material emitted properties? What I'm trying to do is to have the textures of the ground plane reflected onto the object but I don't want the ground plane itself in the image.  If I turn on the alpha option in the ground plane dialog and save the image with background alpha channel I only get a greyscale map of the tiles reflected onto the object but not the tiles.  I've attached the output of a very simple scene to show what I'm after.

The closest I got is to render twice (with and without and do the composition is PS. 

Still not perfect because the ground plane still shows a little ...

Is there a better way?

Thanks in advance


I do this by setting the Environment background to a Color.  Then in the Advanced Background Dialog I set the Reflected Background to an HDRI.  This allows the scene to be reflected into the object without a groundplane.



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