It's a real noob question I know, and it's something I'm ashamed i don't understand how to achieve.

Given a sticker/logo .PNG with transparency alpha, how would i then position said sticker onto the object? I've tried grouping polygon faces and applying a material that uses a texture sop connected to base color and that works in as far as it renders with the logo on it but the alpha isn't honoured and i cant position it appropriately. It also has issues with either stretching or repeating etc etc…

Basically any tips and advice on where to go and how to achieve this would be appreciated. I recognise I'm obviously out of my depth with shaders and texturing and that's where I'm falling down.

You could just create a UV grid and place your decal on the grid. Then use the Ray sop to project the grid points on to the surface of the final target object. This way you can just transform the grid to the location you want and it will deform to the surface of the target object.

Just to clarify I wasn't able to get the alphas to work for *any* of the default .pic files such as the butterfly that come with houdini whilst using the principled shader. Instead I had to use the old classic shader to get things working. I'm sure I'm doing something wrong or being dense but anyway that's all that was ‘wrong’. Now I can do what you say easily enough I guess. But how would I render the logo and the underlying material at the same time without them fighting for position - I've put a polyextrude on mine and given it a low value but that feels like cheating.

* ugg…. translating it I now have a light cyan colour where it should be red / okay I've discovered this has something to do with orientation. Must have got flipped around in the process or something.

Try a small negative lift value on the Ray node to bring the decal off the surface. If you lift far enough, you get a shadow as well.

I find that Mantra really needs full black and white images to do alpha work correctly. That cyan may be the result of Mantra using your image colors as luminance instead of just reading the alpha as it should. So make sure to “spoon feed” the Classic shader a true black and white image, such as the baconAlpha shown in this image.