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Author Topic: Mate plate (dealing with emissive and alpha)  (Read 2673 times)

Roland Witsch

    Reputation: 3
Mate plate (dealing with emissive and alpha)
« on: August 21, 2012, 08:31:48 pm »
August 21, 2012, 08:31:48 pm
Dear all.

I often use 360° panorama photos as background for my visualizations.
This is highly recommended by customers, who will than get a realistic view from their future balcony without the need to model all the environment around the project itself.

sample1: "http://www.witsch.net/lumion/PanoramaSample_01.jpg"
sample2: "http://www.witsch.net/lumion/PanoramaSample_02.jpg"

In any common render software I can switch materials to only emissive (I want the lighting from the photo). But the as I use an alpha maped PNG to fade the upper part of the photos to the sky, I have some problems in Lumion.

1) The photo is no more transparent but white if I increase emissive
2) The cylinder I use as a projection face is throwing shadows to my scene.

So what I request would be
1) the emissive part of the material should not remove transparancy.
2) a switch for such object to define they should not create shadows

Or has anyone any workarounds for me?

Re: Mate plate (dealing with emissive and alpha)
« Reply #1 on: August 21, 2012, 09:38:55 pm »
August 21, 2012, 09:38:55 pm
Dear Roland, look at this:

http://lumion3d.com/forum/special-offers-and-promotions/custom-backgrounds-in-lumion/
Download * CustomBackground.zip (1180.9 KB)

Read careful all the topic.... :D Maybe this can help you ;)
regards

Roland Witsch

    Reputation: 3
Re: Mate plate (dealing with emissive and alpha)
« Reply #2 on: August 21, 2012, 11:56:20 pm »
August 21, 2012, 11:56:20 pm
Thank you for that tip!
I guess that will help me getting forward ...

Re: Mate plate (dealing with emissive and alpha)
« Reply #3 on: August 22, 2012, 10:32:47 am »
August 22, 2012, 10:32:47 am
Hi Roland, the cylinder should not cast shadows on the inside provided that the polygons face 'inwards' and are single-sided.

I don't know which 3D modelling application you're using, but in most of them there are options to make polygons single-sided. Let us know if we can help.

However, it is not possible to create panorama textures that become increasingly transparent in a smooth/linear fashion. The reason is that Lumion only supports 1-bit alpha channels in textures, so a pixel is either visible (white pixel in the alpha channel) or invisible (black pixel in the alpha channel).

Instead, I would recommend that you replace the entire sky/horizon with an inverted hemisphere object as described in the post that arch_bd wrote about. The custom backgrounds sample scene/models also demonstrate which material settings work best for panorama cylinders/hemispheres.

TIP: If you only need to render still images, you could also consider using the Sky alpha map output option to render a mask, so that you can replace the sky manually in Photoshop. However, this doesn't sound like a viable option in your case, since your sky texture also includes horizon objects such as trees etc.
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