Implementing Matte Paintings

Sorry if there is already a Thread like this,

My question is: I am currently working on a scene that has a Matte “textured on to a billboard” ie a plane.
I have found the obvious
that when i render the scene i see a line appear where my sky meets the matte painting, bare in mind i am also using DOV “depth of view” or defocus.
i have also tried to turn down the alpha.

is there any better ways of doing this without billboards, or a way to key out the lines on the edges of the plane billboards?

all your help will be much appreciated

well after searching over google i have found something, of using a “matte/ difference key” Node , if anyone can explain this, i have little knowledge of nodes?

basically i want to get rid of the part of the matte i am not using…

so, in matching up the left edge of the right pic and the right edge of the left pic, there’s a few issues you have to address.

  1. Lens distortion. The size of the image will be different, so you have to subdivide the plane and move the three verts to align the pixels from one to another
  2. Exposure. If your camera auto-exposes, the exposure will be different between the two shots. So, take a swatch of each from both near the edge and subtract them on a gray scale (convertBW) to get an overall difference and apply that via the brightness/contrast node
  3. Color Balance. I think this is the main issue you are seeing, but it is compounded by the exposure issue, so first Exposure correct. Now the issue is that with digital cameras there’s software that changes the color balance from the sensor, which you have to un-do, as well as different light spectrum caused by the changing angle the sun hits the lens. Pros shoot an extra pic of a color card in the context of the scene for each shot and take the difference between them to do color correction. I doubt you have that So, sample the exposure-correct sky and difference them, and then apply that difference as an add to the second image, so that you color-balance one to the other. You may have to apply the difference as an RGB Curve, if Bob has not committed his new nodes. I was working with him on developing some new nodes to solve this very issue.
  4. Cheat. Use a blend texture to alpha out the edge of each; as they overlay they will blend together.

I will try this cheers for the tips, i am finding it is alot harder to composite 2 image nodes that over lap, make my computer run so slow…but cheers Papasmurf.

Have you turned on premul? If your image containd premultiplied alpha, you need to turn on premul (on the image, texture buttons)

OK i kinda noobed out “what the hell just happened BSOD”, sorry but im gonna need an example of this?

because i dont think i didnt it right

cheers Noobie, i feel weird calling you that since im asking the question lol, i will give it a go

The steps I outlined above are applied to each billboard, not in compositing. If you post two of your pics, it might help see exactly what the issues are.

could u possible make a quick example .blend file? i have tried what you have already suggested other I’m not doing it work, or it doesn’t?

Have you got your billboard material set to shadeless?

If you don’t use DOV is it the same?

havent ried this yet will give it a go cheers Yellow :slight_smile:

is there a way of compositing to put a back ground, with out using planes for placing mattes on?