Export 2D image with alpha transparency

[RTCool]

@eneroth3

RTCool, did you only model half the house? I would have expected the windows in your example to show the back faces of the other side, not be alpha transparent.

I know, I was thinking that too. I believe it was just a shell with no interior, and perhaps the back faces were set to transparent, but I’m trying to remember the details.

[sWilliams]

Julia, you are correct to notice that transparency is not working the way you are expecting. This problem seems to have started with SU 2017.

Export .PNG Transparent Background Glitch 2017

Hi Dave, Attached is my sketchup file. I go to file export image .png without a background in styles. Then I drop both the exported .png sketchup image and a background image into a program like inDesign or Pages, and place the .png over the photograph. I avoid inserting images into my sketchup files to keep file sizes down for speedy 3D modeling. Perhaps this is an unknown selection or preset I am missing within sketchup 2017, resulting in user error. I’ll update the post if that is the case…

For demonstration I have created a (somewhat goofy) test model with transparent windows on two sides of a building.
transparency test.skp (233.2 KB)

This PNG image was created with SU2017

The alpha channel in the SU2017 PNG is a solid black region.

The PNG of the same model in SU2015 looks like this.

and the alpha channel in the SU2015 PNG looks to be correct.

I have no idea why this functionality was changed for the 2017 and later editions of SU.

[RTCool]

Well, what do you know? SketchUp 2018 vs. SketchUp 8

2018:

SU8:

Edit:
2018 file saved back to 2016 Pro and exported there:

[Aerilius]

It could be due to improvements of SketchUp’s rendering engine and specific to some graphics cards.

By the way, line weights are surprisingly changing over time! Especially with the 2018 line weights regression (high-dpi scale factor 2×, line width 4×).

[eneroth3]

I’ve only tested with PNG. From what I know it’s the only image format in SketchUp that even has alpha transparency.

@sWilliams

Julia, you are correct to notice that transparency is not working the way you are expecting. This problem seems to have started with SU 2017.

Export .PNG Transparent Background Glitch 2017 SketchUp

I think this is it!

If I remember correctly SU 2017 was the one with a completely reworked rendering pipeline (or was that 2018; I’m getting old).

[RTCool]

TIFF supports transparency. TIFF also can support embedded color profiles while, apparently, PNG cannot? Neither output from SU has a profile, but on a Mac a screen capture does.

[john_drivenupthewall]

I get what you mean finally…

Too achieve ‘true’ transparency on a ‘material’ you now have to set it to 0 on the slider or with code…

the old ‘Intrinsic Alchemy’ engine applied it at a higher threshold, which caused confusion when exporting ‘NFR’ images out of SU…

“why does my building have no glass” type reactions were not uncommon…

for renderer exporters, they just flip it to 0 on the fly…

for compositing you need to do the same…

john

[gsharp]

Sorry everyone… got distracted and missed all the follow up… honestly, i did not notice the transparency type… but it seems to be thoroughly investigated in the subsequent posts