What does sub-pixel accuracy and per-vertex lightning mean ? I see those many places.

I''m not sure but i think it is like this:

Sub-Pixel lighting is when you use lightmaps to light up your objects, which mean that you use a second texture for blending which includes light data.

And i''m sure of per-vertex lightning is when the lighting calculation is done for the vertices only and then interpolated over the face. (this is how it''s done by OGL and D3D)

Another way would be to calculate it for all pixels of the face instead of the vertices, which is only done in ray-traycing progs.

The problem is that a pixel isn''t a maths point, cause a pixel has a size while a point hasn''t.
So we are using an approximation.

If you render the pixel @ say twice the res, you might notice that the 4 pixels that were one in the first pic have not the same color as previously.

Full scene anti aliasing use thise technic to average a pixel color.

sub pixel accuracy :
In fact this mean that you''re pixel isn''t rendered as one pixel but in more than one internaly. The final pixel is more ''realistic'' and true mathematically.

per vertex lighting :

In fact color values due to lighting are computed only at the vertices not on the whole surface.
If the surface looks good it''s because we are using a system called ''gouraud shading'' that use the vertex colors values and the distance between those differents vertices to compute the right surface color at that point.
Try FLAT shading to see how it works when the average vertices color are put on the wall surface.

Hope it helps.


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