This isn’t explicitly a feature request - I was thinking about a way to render raindrops, or other fast-moving particles (such as bullets), and it occurred to me that it would be neat to have a type of billboard that’s only oriented towards the camera along one of the particle-quad’s axes.
Imagine, for example, a fast-moving raindrop, modelled as a quad with a texture on it that shows a greyish, blurry streak, oriented vertically. When the camera is looking forward (horizontal to the ground), a regular billboard will do.
But imagine pointing the camera directly upwards into a rainy sky - from the camera’s perspective, the streaks have all different orientations, pointing directly upwards.
I guess the rules would be this:
- Orient the quad so that it’s longest axis is parallel to the particle’s movement;
- Rotate the quad about its long axis (only) until it faces the camera (or more specifically, so that the camera is on the plane defined by the quad’s surface normal and its long axis).
It might look a little weird when particles are coming directly at the camera, I suppose.
Has anyone heard of this technique?