tzlaine wrote:...normal maps / bump maps for planet textures, instead of pre-rendered shadows on the textures?
I don't want to have planets that look like the cartoon planets in Spore (I like a more realistic look), and that's the sort of relief you'd need to actually see shadows from surface features.
I'm thinking of this mostly for the barren planets, which already have visible shadows on craters. This wouldn't cast long rotating dramatic shadows, but would just cause craters to have dark and light sides consistent with the sun locaction and the planet's rotation.
I agree that it looks artificial. If you were in a system, on the ecliptic, with the ecliptic lined up horizontally in your view, you'd see the planets all tilted at different angles, not all lined up at 90 degrees to the ecliptic.
The planet would be tilted differently, but the shadows would all be aligned vertically. The shadow angle is my point. I think you, and maybe others, are confusing rotation axial tilt and shadow angle, or at least what I'm talking about when refering to them.
To clarify: Shadow angle is the direction the shadow points. Axial tilt is the difference in angle between the normal to the ecliptic plane and the axis about which the planet rotates. Planets all have different axial tilts, but all have the same shadow angle if in the same ecliptic plane.
See image:
What we have now is the middle. The axis (yellow line) and the shadow (cyan dot arc) angles are both tilted as seen by the viewer, and the axis angle is aligned to the shadow (the yellow line connects the ends of the cyan dot arc). The shadow arc indicates the plane of the ecliptic because the sun is also in the ecliptic plane, so the arc angle of the shadow follows the angle of the ecliptic relative to the viewer's "up" direction. If arc and axis are so-aligned, it means that all the planets physically have 0 degree axis tilt angles (relative to the eclicptic) but are just displayed tilted.
To the left, the axis angle and shadow angle are different. The viewer's camera is aligned to the axis angle, so it appears vertical and the shadow is tilted. If we did this (planet axis is vertical) consistently, then all planets would have different shadow angles. This would probably be universally disliked.
To the right, the axis angle is tilted, and the shadow is vertical. This is the one in which the viewer is standing on the ecliptic plane, looking at the planet, which has a rotation axis tilted with respect to the ecliptic plane. I like this one. It's easy to see the planet axial tilt (different for each planet) relative to the vertical shadow and screen "up" direction.