Cheating at 3D

[Ernst Blofeld]

I've written some 3D code which I'm in the middle of testing. It now seems obvious that there's little point in doing the full 3D perspective transformation for any object that's not actually really close to the viewer, the model of a Eurofighter that I'm using to test with becomes only 15 pixels wide when the model is set to 500 metres away. Much further than that and it's not really recognisable and things actually start to break down as the polygons become a bit degenerate. At some point the object just becomes a single pixel, and that's not much fun to watch.

So, I'm thinking of cheating for certain objects that are far enough away and just calculating a center point and then drawing them at fixed scale(s) without the perspective transform. I may even precalculate and blit these objects in.

So, I'm looking for opinions here. Is it going to look bad? Does anyone know of any examples where similar things are done? Should I just use a simpler model for far away objects and forget trying to be clever?

[roondar]

I'm not sure if games used pre-calculated objects to blit in these cases, but I am certain that some games change objects that are far away into smaller or bigger 'points'/filled circles.

Example: Elite 2 does this (more so at lower detail levels) - once objects get far enough they change into first a small filled circle and later into just a dot. I'm pretty sure these stages are just blit (either with Blitter or with CPU) and not actually calculated.

[Ernst Blofeld]

Originally Posted by roondar

I'm not sure if games used pre-calculated objects to blit in these cases, but I am certain that some games change objects that are far away into smaller or bigger 'points'/filled circles.

Example: Elite 2 does this (more so at lower detail levels) - once objects get far enough they change into first a small filled circle and later into just a dot. I'm pretty sure these stages are just blit (either with Blitter or with CPU) and not actually calculated.

I've never played it, I think it came out too late for me, but I've just gone and watched a YouTube video comparing the ST and Amiga versions. It certainly made me feel better about my frame rate.

Edit:

Ok, and my calculator tells me that precalculating isn't really an option for space reasons, so it's probably more about how I go about simplifying the models, and whether or not and how I can drop the perspective transform.