Beispiel fuer ein Vertexprogramm
Dieser Beispielcode und der Screenshot entstammen einem kleinen OpenGL
Programm aus dem Cg-Toolkit von Nvidia, welches auch
den hier abgebildeten
Assmblercode zur Programmierung des Vertexshader
nutzt.
Hier der Triceratops mit einer verdrehten
Wirbelsaeule.
Und hier der dafuer verantwortliche Assemblercode
fuer den Vertexshader:
!!VP1.0
# Twist
MOV R0, v[OPOS];
MUL R1.x, R0.x, c[61].x; # frequency
#
calculate sin(angle) and cos(angle)
ADD R1.y, R1.x, -c[62].w; # R1.y = R1.x + PI/2.0
#
reduce to period of 2*PI
MUL R2, R1, c[62].x; # R2 = R1 / 2.0 * PI
EXP R3.y, R2.x; # R2.y = R2.x - floor(R2.x)
MOV R3.x, R3.y;
EXP R3.y, R2.y; # R2.y = R2.x - floor(R2.x)
MAD R2, R3, c[62].y, -c[62].z; # R2 = (R3 * 2.0*PI) - M_PI
# R4.x
= sin(R2.x);
# R4.y
= cos(R2.y);
#
parallel taylor series
MUL R3,
R2, R2;
MAD R4, -R3, c[63].w, c[63].z;
MAD R4, R4, -R3, c[63].y;
MAD R4, R4, -R3, c[63].x;
MUL R4, R4, R2;
#
x y z w
# R:
#
1 0 0 0
#
0 c -s 0
#
0 s c 0
#
0 0 0 1
# c
= cos(a)
# s
= sin(a)
#
calculate rotation around X
MOV R1, R0;
MUL R1.y, R0.y, R4.y;
MAD R1.y, R0.z, -R4.x, R1.y; # ny = y*cos(a) - z*sin(a)
MUL R1.z, R0.y, R4.x;
MAD R1.z, R0.z, R4.y, R1.z; # nz = y*sin(a) + z*cos(a)
DP4 o[HPOS].x, c[0], R1; # object x MVP -> clip
DP4 o[HPOS].y, c[1], R1;
DP4 o[HPOS].z, c[2], R1;
DP4 o[HPOS].w, c[3], R1;
#
rotate normal
MOV R2, v[NRML];
MUL R2.y, v[NRML].y, R4.y;
MAD R2.y, v[NRML].z, -R4.x, R2.y; # ny = y*cos(a) - z*sin(a)
MUL R2.z, v[NRML].y, R4.x;
MAD R2.z, v[NRML].z, R4.y, R2.z; # nz = y*sin(a) + z*cos(a)
# diffuse
lighting
DP3 R1.x, c[4], R2; # normal x MV-1T -> lighting normal
DP3 R1.y, c[5], R2;
DP3 R1.z,
c[6], R2;
DP3 R3, c[32], R1; # light position DOT normal
MUL o[COL0].xyz, R3, c[35]; # col = ldotn * diffuse
MOV o[TEX0], v[TEX0];
END