Needed feature : Flat Background image mapping for rendering

[OctaneFX]

I love Octane but I can't see a feature I really need : it'll be great to be able to import an image as a flat background image (without distortion) equaling the render size, and working in complement with the spherical Environment texture. So we'll be able to render the background image with objects receiving reflections of the spherical Environment texture.
Is it a feature in your plans ?

[DayVids]

For right now you can use a single flat image in the BG and scale it to repeat until matches your desired image, and it can function as an HDRI for lighting, but you can use emitters out of camera to create whatever lighting you need or to highlight certain things.

I had to do this for a mailer banner that I will be posting soon.

[OctaneFX]

Thank you for your help, but in my case, I don't want to use the background image as a HDRI image (I don't want reflections of the background image on the objects). I don't want to tile the image because the method is impracticable for my animation purpose.
In your example, if you rescale the image to the screen you have a visible tiling image effect on high reflective objects like metal (it's doesn't match). You also have a perspective distortion of your image and if you rotate the object in the viewport or change the FOV you lose all your settings
I only want a STATIC scaled renderable image in the background that fit the screen size and that doesn't interact with the scene parameters. If only Octane could import background image animation like MentalRay does, it'll be awesome !

[Lutze]

This is usualy (and better) done in post in almost every 3d app I know. Just render out your beauty-pass, render out an alpha-pass (in the case of Octane: all black model done with mateial settings and a pure white background) and comp your BG image over. This way you have absolute control over the final result.

Lutze

[OctaneFX]

Thank you very much Lutze, but do you know if we can render an alpha pass in the pre Beta of Octane ? I don't find the functionality when saving a .png file. I only know that the final 1.0 will support alpha chanel.
I don't think that it works with a pure background as a texture environment because the white is reflected on the geometry. See example bellow :

[colorlabs]

He described how to make an alpha pass in his post - just set all the materials in your scene to pure black diffuse, and use a pure white HDR texture (e.g. floattexture turned way up). I've never done it but a lot of people seem to do it this way.

[Lutze]

Yes, you have to render it twice as an alpha pass is not yet implemented in Octane. Therefor you have to build your own alpha pass by rendering the scene a second time with all materials set to pure black and the background to pure white. The lighting in your original beauty-pass has nothing to do with it whatsoever.

Lutze

[OctaneFX]

Thanks all for the tricks.
The disaventage of the technique is that you have to render twice, so it's right for stills but it's impracticable for animation.