Grey line around parts?

[maf1909]

I've been trying to use keyshot to create images we can layer on our website to change the color of products, and I'm having trouble with getting a line of grey pixels around the parts, which I assume has something to do with how the part edge is blending into the alpha layer or something.  Essentially I need to render each part of a product individually, then stack all the images of that part along with all the images of any other parts of the same product.

The images below are a test I tried using two cubes.  They're flush, as the screenshot shows, so there's no gap between them.  However, if I render the two separately and stack them in photoshop, I get a grey line between them (layered.png), which doesn't look good if I were to have two different color cubes. 

Is there a way to do what I want without having a ton of extra work in photoshop or something?  Each product we do has 58 different colors in 2 finishes, so it'd be a huge amount of work to have to tweak each image in photoshop.  I'm probably trying to simplify something that isn't nearly this simple, but hopefully someone can enlighten me 

[Rex]

You are absolutely correct that this has to do with the blending of the edge with the alpha channel.

There are basically three solutions:

1. Use a background image to fill in the areas of semi-transparent pixels.
2. Render at a higher resolution and reduce the size of the image so the areas of semi-transparent pixels are no longer noticeable.
3. Create an action in Photoshop that duplicates the layer enough times to turn the semi-transparent pixels opaque and apply that action to every image.

Hope that helps!

[philw]

A 1-pixel de-fringe is all that I generally need in Photoshop to make it not noticeable (depending on size of image). When I'm animating and compositing in After Effects I just run a 1 pixel choke as a filter effect on the frames and that sorts it out too rather than having to doctor each frame in Photoshop.

You could run a scripted Photoshop action on the folder of images to achieve? As Rex says, maybe start at higher res than you need and a combination of the de-fringe and reduction in size should sort you out...

[maf1909]

what I ended up doing was rendering all layers to photoshop, because that gave me a full RGB layer of all the parts, and then I ran an action in photoshop that would duplicate that RGB layer, trim it to match the outline of each of the other layers, then export from there to PNG.  That, while cumbersome, worked pretty good.  Granted, I only had 2 parts, so a product with a dozen parts is going to be a major pain, but if that's what it takes to work, that's what I'll do.