Book 2.4.6, "standard" projection

[whydoubt]

Having worked with geographic projections extensively, I would not say there is such thing as a "standard" projection. There are several popular projections suited for various needs (and plenty more less popular ones). As for the type of projection that matches the mapping equations used in this section, any image using an "equirectangular" projection would work.

[hollasch]

Rectangular is probably sufficient. We just need continental blobs somewhere as we're just looking for something pretty. Actually, there's no need for users to go grab anything, as we include images/earthmap.jpg in the project already.

Might just add a suggestion to play with other rectangular image sources for fun. I'll reword a bit.

[whydoubt]

Mercator is another common rectangular projection, but it is not equirectangular. Same with Gall-Peters, though much less common. You would need to use different formulas to render those correctly.

I do like idea of suggesting trying other sources, as maybe it could give someone more of an appreciation of projections and texture mapping in general.