Houdini 19.5 Compositing

Compositing tips and tricks

Working with High Dynamic Range images

High Dynamic Range (HDR) images provide much more flexibility for compositors by providing much more color information. However, they also cause some problems in compositing:

  • Using color correction operations, you can easily create colors with negative or super-white components when doing normal color corrections. Negative color components can cause unexpected results when compositing over other images.

  • Alpha can also be drawn outside the 0-1 range. This produces strange results when using compositing operations that depend on alpha to blend (over, inside, and XOR).

  • HDR colors don’t work well with the screen compositing operation, which will cause some odd color shifts.

  • Applying gamma to HDR images, especially low gamma, can cause super-whites to become extremely bright.

  • LUTs have a limited range, usually black-white. Applying a such a LUT can cause unwanted clipping of HDR information

To reduce these problems:

  • Use a limit COP to clamp HDR information where it is not needed.

  • Use color curves for finer control over HDR ranges (Color Curve COP).

  • Convert alpha to 16bit int.




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