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I am trying to composite a background into a rendered image with alpha channel. i am following this tutorial from Tom. But when i get to the step of pasting in the alpha into a layer mask, I can not get a new blank window to open for the layer mask. When i select the layer mask on the right of my maxwell render and paste, I just get a new regular layer with the alpha channel.

http://www.maxwellrender.com/forum/view ... 90db3036be


Please help explain!

Switch to channels tab, find your layer mask there and paste it. I forgot which key combination it is to paste it directly in the layer mask in the layers palette....

Go to your Channels, get a new Alpha layer (it will be blank), paste your alpha into that. Then Select that alpha, go to your render layer and save selcection (your alpha) and in the drop down menu for channel, choose the italics it will be called your render layer mask. It is one of the options in the Selection/Save selection pull down menu.

Quick answer, but hope you can work it out from that.

Regards,
Bim

Thanks guys. Going to channels and selecting the alpha channel and pasting still pastes the copied alpha into all 4 channels even though I only have the 4th channel selected. Almost there, but still struggling! Any suggestions?

Daniel,

When you go to the chanels tab, make a new channel, highlight it in the list, your window should go black (or white), then paste. That should paste the alpha only into the one channel only.

Select this alpha, (pull down menu Selection/Load Selection...), got to your render layer in the Layers pallete, (should be visible in your window), make sure your render layer is highlighted, then go to pull down menu Selection/Save Selection... save it as a Layer mask.

Kepp trying you're almost there.

Bim

You guys do it the hard way. Just alt-click the blank apha mask space (in the layer list) and paste!

Thanks everyone. In the end, i just could not do the alpha mask box / paste as Bubbaloo or flower suggested. Clicking the alpha box and pasting overwrites the whole RGB image. I also tried to do it in the channels window and created a new channel and selected it / pasted and the RG&B channels also took the paste data, overwriting my render. I could not determine a way to work around that problem.

My crisis was averted at the last minute. In the end, I used Fernando Tella's link to Tom's Photoshop script and that did things nicely and with one click. Now I have it for future composite work. Thanks Tom!!!

And Thank you again for all the experts who take the time to chime in on such an urgent call for help. I only had about 1/2 hour to get this to work and for a moment I thought there was not even enough time to write the forum. Thankfully this forum has such a quick response time!

I owe you all a beer someday.

I agree with Bubbaloo.

Also, Maxwell alpha always leaves a black or white border/stroke around the edges. To remove that, you add a layer under the masked one and you merge the two. Then you go to Layer/Matting/Remove black/white Matte or defringe depending on the circumstances. Leaves you with a perfectly masked layer....

Hope this helped some of you...

Kyriakos Tsouloupas wrote:I agree with Bubbaloo.

Also, Maxwell alpha always leaves a black or white border/stroke around the edges. To remove that, you add a layer under the masked one and you merge the two. Then you go to Layer/Matting/Remove black/white Matte or defringe depending on the circumstances. Leaves you with a perfectly masked layer....

Hope this helped some of you...

This is because PS doesn't do an automatic matte removal like other compositing applications, you have to do it manually. You don't have to first merge it with another layer. After you applied the alpha to the layer, just use Remove black matte.