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Texture Painting with Alpha
I’m fairly new to Cinema 4D and multi channel painting
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10 Replies
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Did you place the image into the alpha channel section of your material? Also make sure you’ve then selected the alpha channel in the layers dialogue. I find PSD files work best for this.
Noah
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Thanks for the speedy response.
I think perhaps I’m getting confused about the logic of the situation. I’ve got a texture UV mapped onto a model, in this case a a complex model like the flower of a rose. I’d like to projection paint an image of the text “test” (or whatever) over the existing texture. The “test” image has yellow text but everything else is masked by alpha. Without interfering with the alpha of the rose texture, I just want the text to be drawn on the projection, so that I don’t get the nasty black background sprayed on as well. I guess the real question is whether the texture plane that you paint on with a projection can accept alpha.
I figured out an alternative way to do this, but it’s clumsy: I’ve pasted my “test” image, black and all, onto the projection, let it apply to the rose, then pasted the alpha channel grayscale into the layer mask for the image. This is fairly effective, but unfortunately since the projection needs to apply between pasting the “test” image and the mask, the results are uneven and pixellated.
Any thoughts?
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This is a good tutorial that helped me get the hang of it:
https://www.c4dcafe.com/ipb/index.php?download=80
Noah
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Thanks. I’ll give this a whirl and see how it goes.
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When you say ‘projection paint’ it makes me think you’re in Bodypaint. In fact I’m sure you are. But I think you might be making it harder than it is. Since you already have your flower, might as well just slate that and not throw another layer on it. If you load the image and its matte into another material and apply to the right of the first, leaving ‘mix textures’ unticked, you get an applique of that image. This is called ‘alpha mapping.’ Rather than go through all the steps involved in Bodypaint, you might as well go to whatever angle you want and use ‘Flat’ as a projection, abetted by ‘Fit to Object’ / ‘Fit to Region’ (and drawing the region). Then use the texture / texture axis tool to scale and position it how you want.
But text on a flower is hard to picture, so I’m not sure I’m reading you. And then there’s that term ‘multichannel painting,’ which again is a very cool BP function but is it really necessary here?
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This definitely seems like an easy way to do something similar to what I wanted. Those basics…!
Still, the flat projection doesn’t really come out very well against an object as complex as this flower, while the projection paint hit all the surfaces right so that at the perfect angle the text on the flower is legible, while even slightly off it is garbled nonsense. This is the effect I was looking for. I still haven’t taken Noah’s tutorial yet, though, so there is almost certainly a way of achieving a better result in the program than what I did.
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Oh, you’re putting text on the flower itself? Wow, that’ll resolve from exactly one angle, the angle you paint from. So painting is the thing, and you do mean bodypaint, eh?
You shouldn’t need to worry about the alpha if you load your text image from a psd with a transparent background. Load it, open it in your texture window, marquee it, copy, select your viewport showing your flower model, and paste it there. I think that’s what you’re getting at, but it’s much like flat mapping. You’ll get ‘shadows’ where the text image didn’t paste, which you could always fill in by painting with a brush.
I’d just be careful with layers in bodypaint. Make sure you’re doing everything to different layers, basically, just like photoshop.
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Yep, that’s what I’m doing!
Thanks for the tip about pasting the texture into the viewport, I hadn’t realized you could just do that. Also I’ll review my psd. My texture had a black background that wasn’t being covered by the alpha channel, but you’re saying a transparent background will be masked? I just removed the black background but when I paste the new psd with a transparent background into my viewport the part that should be transparent turns gray in the projection layer. I guess that the way Bodypaint splits an image into color, alpha, bump etc. channels means that you can’t paste more than one simultaneously into the projection layer?
Hmmm.
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That’s a good question. I’ve wanted to paste an image into multiple channels myself but ended up just doing it multiple times, once into each channel. I activated each channel and pasted into each separately rather than having them all activated at once, because on my first try, with them all on, the paste only happened in the color channel. Luckily the texture stays put, and if you’re marqueeing the whole thing and not moving your camera, the registration on the images won’t be offset.
As for the gray, still not sure about that. When you load an image, I think I just noticed the other day that the layer manager will show you the actual layers of the psd you opened. So you can turn off layers that aren’t used if you want.
The Vital Distraction Bodypaint dvd is a good place to learn all this stuff. They had it at the last place I worked. I need to go there to watch it a second time to get all the tricks down.
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Well thanks for the reference and for the help. It’s been very useful and a lot of fun, too.
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