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alpha channel not working

Posted: Thu Dec 24, 2015 2:22 pm
by Manser
I am using Skindigo with Indigo Renderer 3.8.26 for Mac OSX 10.9.5.

Apologies in advance if this is a pedestrian question, but I cannot find the answer anywhere in the manual or this forum.

I want to render an alpha channel. I go to Settings/Advanced/Foreground Alpha and check the box.
I hit render - and it renders the full scene. No alpha.

I try selecting only geometry I want the alpha for, hit render. No alpha.

I try deleting the entire rest of the model, leaving ONLY the geometry I need the alpha for, hit render. No alpha.

I seem to remember older versions of this software would render black/white alpha channel very easily. I understand the new version of this software will render the object over a checkerboard background as shown in the manual, but I can't figure out why I'm not getting that.

Again, I keep getting the full rendered scene even though "foreground alpha" is checked.

Thanks in advance.

Re: alpha channel not working

Posted: Sun Dec 27, 2015 12:54 pm
by Oscar J
Could you perhaps post a pic of your scene?

Re: alpha channel not working

Posted: Mon Dec 28, 2015 1:36 am
by contegufo

In Skindigo, Render setting, Advanced, checkbox Foreground Alpha, APPLY.
In Indigo gui appear in the image with the bottom squared.

Re: alpha channel not working

Posted: Mon Dec 28, 2015 3:45 am
by thesquirell
Soooo, just fill that layer inside photoshop over a black background, and create your own. The main thing is that you have your backgroundless image, so you can create whatever you want. And you don't even have to wait for it to sample it to some higher number, since you'll be filling your layer with solid white/black. :D

Re: alpha channel not working

Posted: Tue Dec 29, 2015 2:04 pm
by Manser
Thank you all for your replies.

I am attaching an image of my shot as suggested by Oscar J

thesquirrel - soooo, I don't have any available layers in photoshop. It's one flat .png. That's why I'm here. ;) Indigo is not rendering a separate alpha channel as it should when foreground alpha is checked.

contegufo - that's exactly what I am doing! But I am not getting the image with the checkerboard like yours. As I mentioned, I keep getting the fully rendered scene.

This is the .png from my renders with the foreground alpha selected. I am trying to get an alpha channel for the walkers only. As you can see, it renders the whole scene. I've tried selecting only the walkers. I've tried deleting the background image entirely. It still renders the entire scene, even when everything but the walkers is deleted! You can see the Sketchup blue sky to the left and right of background. At the very least, that should be a checkerboard.

It's like Indigo is not clearing a cache between renders, it keeps rendering the same model, regardless if the model or render settings have changed.


Re: alpha channel not working

Posted: Tue Dec 29, 2015 7:37 pm
by bubs
OK, it would seem to me there's more than one issue here. Firstly the alpha of the walkers will never work with an image behind it within sketchup, because that image is applied to actual geometry, and so will render as an object... The only things indigo will ignore are true background items, ie sketchup sun and sky or an environment map background.
Your second problem is the one of indigo still rendering things you have deleted (trying to solve the original problem). This is a bit more perplexing... Do you by any chance have everything grouped or as a component? There are ongoing issues within skindigo of changes made to grouped or component items' textures not applying if they.have been previously exported to indigo (I suspect something wrong with the quick export that was implemented but have never had this confirmed). Although I have to say I do not recall it happening with anything other than textures... Anyway, if you DO have everything grouped or as a component, try exploding and (if necessary) regrouping, this is the only work around I have found to sort the texture issue and something similar might be at play here... Best of luck!

Re: alpha channel not working

Posted: Tue Dec 29, 2015 11:16 pm
by Pibuz
BTW, Indigo never rendered a separate alpha channel. It simply renders the GEOMETRY (with textures, materials and so on) and makes the sky transparent. So, you can put your favourite background in PS, creating a new level and puttin it backwards.

Re: alpha channel not working

Posted: Wed Dec 30, 2015 12:03 am
by Oscar J
Pibuz: actually it did. Foreground alpha wasn't introduced until 3.6.

Re: alpha channel not working

Posted: Wed Dec 30, 2015 3:42 am
by Pibuz
Oh're right!
I forgot...sorry guys!

Re: alpha channel not working

Posted: Wed Dec 30, 2015 11:13 am
by Manser
Thank you Pibuz and Oscar J for your replies.

We have success!!! Pibuz, yes, the walkers are all components. I just grabbed them off the web. By exploding them, and deleting the background image and the ground plane, I was able to get Indigo to render an alpha.

I understand what you mean about how Indigo will always render an "in model" background image, and my problem was that Indigo continues to render it even if I deleted it. But once I exploded the components, that did the trick and it re-loaded the model properly.

Yipes - never would have thought of that. thank you!

Before upgrading to 3.8, I was using a version prior to 3.6 and the alpha rendering was handled quite differently.

Thank you guys for your help. cheers.

Re: alpha channel not working

Posted: Wed Dec 30, 2015 12:00 pm
by Oscar J
Glad it's working now. :) Cool scene btw, looking forward to seeing more of that. :wink: