Correct an important bug in the vertex shader.
b = 1/a if a!=0, 1 otherwise was incorrectly computed as b = 1.0 / (a+1.0-sign(a)). This, when 0<a<2^-24, suffers from 'round-off error': then a+1.0 = 1.0 (sic!) thus b = 1/0 !.
Correct way: b = 1.0 / ( a - (sign(a)-1.0) )
Correct an important bug in the vertex shader.
b = 1/a if a!=0, 1 otherwise was incorrectly computed as b = 1.0 / (a+1.0-sign(a)). This, when 0<a<2^-24, suffers from 'round-off error': then a+1.0 = 1.0 (sic!) thus b = 1/0 !.
Correct way: b = 1.0 / ( a - (sign(a)-1.0) )