原文：http://www.saltgames.com/2011/stage-3d-shader-cheatsheet/
Operations
available to shaders:
available to shaders:
-
mov t
a - Copy the contents of a into t. -
add
t a b - Add a and b,
put result in t. -
sub
t a b – Subtract b from a,
put result in t. -
mul
t a b – Multiple a and b,
put result in t.
When working component-wise this operation doesn’t always do as I’d expect. Specifically performing the operation:
mul
vt0.xy va0.xy vc0.xy
Gives a different result from performing the two operations:
mul
vt0.x va0.x vc0.x
mul vt0.y va0.y vc0.y
Whereas they would give the same result if it were an add operation
in both instances instead of mul.
I’ve yet to work out exactly what the mul operation
does with multiple components. -
div
t a b – Divide a by b,
put result in t.
The same behaviour as outlined above for the mul operation
applies to div too. -
rcp
t a – Divide 1 by a,
put result in t. -
min
t a b – Copy whichever of a or b is
smaller into t. -
max
t a b – Copy whichever of a or b is
larger into t. -
frc
t a – Copy just the fractional part of a into t.
e.g. if a has
the value 5.86 then 0.86 is placed in t. -
sqt
t a - Find the square root of a,
put result in t. -
rsq
t a – Find 1 divided by the square root of a,
put result in t. -
pow
t a b – Raise a to
the power of b,
put result in t. -
log
t a – Find the binary
logarithm of a,
put result in t. -
exp
t a – Raise 2 to the power of a,
put result in t. -
nrm
t a – Normalise the
vector given in a (keep
same direction, but make it length 1), put result in t. -
sin
t a – Find the sine of a,
put result in t. -
cos
t a – Find the cosine of a,
put result in t. -
crs
t a b – Find the cross
product of the vectors a and b,
put result in t. -
dp3
t a b – Find the dot
product of the three-dimensional vectors a and b,
put result in t. -
dp4
t a b – Find the dot
product of the four-dimensional vectors a and b,
put result int. -
abs
t a – Find the absolute
value of a, put result in t. -
neg
t a – Multiply a by -1, put result in t. -
sat
t a – Clamp a between
1 and 0, put result in t.
e.g. if a is
-4.6, 0 will be placed in t.
If a is
0.6, 0.6 will be placed in t.
If a is
8.2, 1 will be placed in t. -
m33
t a b – Perform a 3×3 matrix multiply on a and b,
put result in t. -
m44
t a b – Perform a 4×4 matrix multiply on a and b,
put result in t. -
m34
t a b – Perform a 3×4 matrix multiply on