OTOY Forums

Hi forum,

I have to rerender a part of an animation. To shorten rendertimes, I made a plane in front of the camera and booled a hole in it. The plane got a diffuse material, diffuse channel colored black and matte option switched on. I aspected that the plane will be rendered black and could be saved as an alpha part of the picture, stancing the scene seen in the hole. This technique works the same way in Cinema.
But the plane gets white and even colored by the daylight environment and no alpha is seen or saved. Is there another workaround for that?

dinf wrote:Hi forum,

I have to rerender a part of an animation. To shorten rendertimes, I made a plane in front of the camera and booled a hole in it. The plane got a diffuse material, diffuse channel colored black and matte option switched on. I aspected that the plane will be rendered black and could be saved as an alpha part of the picture, stancing the scene seen in the hole. This technique works the same way in Cinema.
But the plane gets white and even colored by the daylight environment and no alpha is seen or saved. Is there another workaround for that?

i think something is wrong. it must be work if you ajust the color to black and use diffuse material. sound seems like not diffuse material

dinf wrote:Hi forum,

I have to rerender a part of an animation. To shorten rendertimes, I made a plane in front of the camera and booled a hole in it. The plane got a diffuse material, diffuse channel colored black and matte option switched on. I aspected that the plane will be rendered black and could be saved as an alpha part of the picture, stancing the scene seen in the hole. This technique works the same way in Cinema.
But the plane gets white and even colored by the daylight environment and no alpha is seen or saved. Is there another workaround for that?

Dinf

if you mean , like this....see below the screen grab

do what you should usually never do....Reverse the normal's so they face inwards, away from the camera position and give the plane a black colour.

Jaba

aoktar wrote:i think something is wrong. it must be work if you ajust the color to black and use diffuse material. sound seems like not diffuse material

Oh hi Ahmet, didn't see your response Yes it is diffuse material, the only one with matte option. I checked matte, smooth and diffuse channel wich is switched to black.

Hi Jaba, thank you for your help!
I can change the direction of the normals as I want, the plane stays white.
Did you activate 'matte' in the material? Will Octane render black and an alpha map at the place of the plane?

Oh, sorry. I did the wrong kernel settings and switched environment on and alphachannel of. The other way plus premultiplied alpha in the camera tag works. Without premulti I got many hotpixel wich I can't remove with the hotpixel settings. Wich leads to another problem since the alphachannel leaves a black edge at the boole intersection.

But I won't use this technique now. On one hand Cinemas picture viewer seems to be unable to save this alpha (or again I did some wrong settings) and on the other hand the render difference between the blocked image and the whole image is around 2%, so I can also re-render the part as complete pictures.

Nevertheless thank you both!

I have to ask again.

This time I masked out all geometry but some moved objects. The moved ones are in a hugh machine wich covers them partially. So I put on everything that could cover the black colered matte material. And I get this:



The white areas are alpha masked as wished. But the black ones should be masked out, too.
As Jaberwocky mentioned, these are the polygons with normals showing towards the camera. I can't switch them all in direction, they are just too much. And some of them will turn into camera direction again later on due to movement of the camera.

Is this the way it is ment to be or did I do something wrong again? This time alpha channel is checked

Edit: sorry for the bad quality, didn't check changed compression settings. But it is also the same problem in better quality.