Returning a given texture coord in 3d space

is there a way of finding out a where in 3d space a point on a texture is?

for example, say i have an object with a texture loaded into texture layer 1. How could i find out the x,y,z coords of every pixel in the texture?

ie
for x= 0 to texturewidth(blah)-1
for y= 0 to texturewidth(blah)-1
.
.
somehow find out the x,y,z of each point
.
.
next
next