compositing question

Support Compositing and Post Processing
1

Hi guys,I’m trying to do a scene where there are seven big asteroids (like Andrew Price tutorial) an earth and moon plus a big star field texture. My computer will blow up if I have more than 1 asteroid on screen My question is, through compositing, is it possible to render all these separately and add them in after? It’s for animation if that makes any difference. Also, would they all still be effected by each others shadows and such?I’m a complete noob at compositing, but I would love for the asteroids to be leaving a tail behind, or some sort of debree trail. How would the best way to go about this also? I’m using cycles.Many thanks.Tyko

2

The answer is, “yes.” Although you must really have a small computer if it blows-up on “one asteroid,” or perhaps you are unknowingly doing something wrong.

Anyhow: to deal with this problem properly, if using compositing, you’ll need to keep a few very key things in mind:

  • You should use the MultiLayer OpenEXR file format, which captures complete digital datasets with each “channel” of information broken-out separately. This also puts each frame into a separate file so that, if it crashes, you can resume where you left off.
  • You will need to capture RGB, Alpha, and Z-depth (“distance from camera”).
  • You will need to be sure that the images contain nothing where there is nothing … no “world colors,” “ambient lights,” and so-on. You should measure the black-areas to be sure that both RGB and Alpha really are “zeros.”
  • Use scenes, or separate files. You want to be sure that the cameras and lights are the same for each shot.
  • You will use nodes such as AlphaOver and Z-combine to tell Blender how to merge the overlapping areas during the compositing step.
  • “Try it first with one frame,” and with selected frames, to be sure that you’ve got it right before you render everything-else.

Also, if it’s an asteroid field, take a little lesson from Walt Disney and 101 Dalmatians, which was the first known use of a Xerox machine in an animation project. Maybe you can render a few asteroids, bulls-eye centered at (0,0,0) on the screen, shooting a few seconds on either side of the total length-of-time required. Then, using the compositor, you can offset and scale that one image, with a starting-frame offset so that the rocks aren’t synchronized. The result might be a perfectly-satisfactory field-of-rocks with much less actual computing-time required. (It’s called “faking the shot,” and that’s a good​ thing.)

3

Thanks for the steps :stuck_out_tongue:

Ok I wouldn’t say ‘blow up’ but it gets a little choppy :slight_smile: I have an asteroid and an 8k texture for the environment background. I still need to get six more roids in, the earth and the moon :frowning: