I’ve encountered two instances that suggest there’s some funny truncating taking place somewhere in either OSPRay or the OSPRay/VTK interface. Essentially, it comes down to the fact that colors are not coming back quite right.
- Set the ospray render node to “scivis”
- Set the background to some arbitrary value (e.g., 230, 240, 250) as a normalized color(e.g., 230 / 255.0, etc.).
- Render an empty scene
- Export the image.
The image should be full of (230, 240, 250)-valued pixels. What you actually get is (229, 239, 249). However if I take my normalized color as:
(r + 0.5) / 255, (g + 0.5) / 255, (b + 0.5) / 255, I get the correct background color out.
- Set the render node to “pathtracer”
- set per simple samples to 1.
- Put some arbitrary simply geometry in front of the camera.
- Shine a light on it and create some insanely high intensity for the camera – the goal is to clearly flood the scene such that we get a white out.
- Export image
- The color saturates, not to (255, 255, 255) but to (254, 254, 254).
This could still be a truncation error (i.e., any value, even a slight epsilon below 1 will end up converting to 254), although that seems highly unlikely with a single sample per pixel and intensity ranked to the sky. I’d hope it would cleanly saturate to 1 and then directly map to 255.