# note:   lightFallTC = fragment.texcoord[2]
#         lightProjTC = fragment.texcoord[3]

# calculate point light tc
MOV    R1, lightProjTC;
MOV    R1.z, lightFallTC.x;
MAD    R1.xyz, R1, 2.0, -1.0;

# calculate projected light tc
MOV    R2, lightProjTC;
MOV    R2.z, -1.0;
RCP    R2.w, lightProjTC.w;
MUL    R2.xy, R2, R2.w;
MAD    R2.xy, R2, 2.0, -1.0;

# sample projection cube map
TEX    lightCube, R1, texture[3], CUBE;
TEX    lightProj, R2, texture[3], CUBE;

# calculate attenuation (x = point, y = projected)
DP3    R1.x, R1, R1;
POW    R1.x, R1.x, 0.5.x;
MOV    R1.y, lightFallTC.x;
ADD_SAT R1.xy, 1.0, -R1;
MUL    R1.xy, R1, R1;
MUL    lightCube, lightCube, R1.x;
MUL    lightProj, lightProj, R1.y;

# if w > 1.0, light = projected, else light = point
SLT    R1.x, 1.0, lightProjTC.w;
CMP    atten, -R1.x, lightProj, lightCube;