I don't know that code and I don't much about how efficient cpus
calculate mathematics,
but I state some ideas anyway:
> i did maths so i would have plenty of ideas to make the clouds prettier and
> more
> structured but it gets too expensive even now.
You could try to compile the dynamic cloud files with the gcc's
-ffast-math flag.
> (a=f(x,y,t), r=g=b=sin(t)*df/dx+cos(t)*df/dy+128 to get clouds lit from a
> wandering sun. as nobody knows how shadows are drawn on a torus with a sun,
> this
> should maybe not be done using sin/cos ;)
Don't worry to much about this. Globs live on a topological torus -
geometrically our torus
cannot exist.
Looks like you use a small Taylor polynomials for cos and calculate it using the
Horner scheme. I don't think this can be made faster.
Or could we use some discrete calculation for approximation?
PerlinNoise.cpp:
1.
unsigned PerlinNoise::permutationTable[ NOISE_WRAP_INDEX*2 + 2 ] = { 0 };
We could use a left shift:
unsigned PerlinNoise::permutationTable[ NOISE_WRAP_INDEX<<1 + 2 ] = { 0 };
2.
Instead of:
float val, amp = 1.0, sum = 0.0;
for ( int i = 0;i < oct;i++, amp *= 0.5, tp *= 2.0 ) {
val = Noise3d( f_tp );
if ( hard ) val = fabs( val );
sum += amp * val;
}
return 0.5 + 0.5*( sum * ( ( float ) ( 1 << oct ) / ( float ) ( ( 1
<< ( oct + 1 ) ) - 1 ) ) );
We could try:
float val, sum = 0.0;
for ( int i = 0;i < oct;i++, tp *= 2.0 ) {
val = Noise3d( f_tp );
if ( hard ) val = fabs( val );
sum += val / (float) (1<<i);
}
return 0.5 + 0.5*( sum * ( ( float ) ( 1 << oct ) / ( float ) ( ( 1
<< ( oct + 1 ) ) - 1 ) ) );
But that is probably worse.
Hey why isn't there a thing like float-shift? After all this would
only require to add/subtract 1 from the exponent!
Google tells me there is such a thing:
/**
* While we're on the subject, someone might have use for these as well?
* Float Shift Left and Float Shift Right. Do what you want with this.
*/
void fast_BSL(double &x, register unsigned long shiftAmount) {
*(unsigned long*)&x+=shiftAmount<<23;
}
void fast_BSR(double &x, register unsigned long shiftAmount) {
*(unsigned long*)&x-=shiftAmount<<23;
}
http://mail.flightgear.org/pipermail/simgear-cvslogs/2003-June/000533.html
3.
DynamicClouds.cpp:
vpX += (viewPortX-vpX%64+96)%64-32;
This might be faster using a mask:
vpX += (viewPortX-vpX&63+96)&63-32;
--
Kai Antweiler
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