I thought it would be better to just post my question/problem using images. I am not able to paint or drag a mask onto the side of a cube, without the mask projecting onto the top of the cube. Please see image to understand what I mean. Thanks.
hide what you don’t want masked, which is easier to do with polygrouping as well.
You can’t mask a single face of a cube. The reason is that masking is effectively done by vertex, not by polygon. If you mask the whole of the side then the vertices at the edges of the face will be masked, along with all the others. Those edge vertices are also on the edges of polygons on the other sides. Those polygons have some vertices masked and some not, so their masking will be 50%.
The best you can do is to divide your cube so that all the polygons are small. That way the edge polygons that are 50% masked will be very close to the face.
HTH,
How exactly would you hide something, actually I found out how, thanks. 
Marcus. thanks for the reply. You said to divide the cube so that all the polygons are small. I divided the cube and the mask still flows over the top. I don’t want to divide it too much before importing as I want my it to remain low poly for a game asset.
OK, so long as you understand the limitations.
The easiest way to mask a single side is to:
- Turn off perspective and position the cube so that it is absolutely square on the canvas. Hold down Shift after starting to rotate the cube and it will snap to position.
- Hold down Ctrl and then click off the model and drag so that a very thin sliver of masking is along one edge of your cube. Rotate the cube and you will find that the whole of the face that is on that edge has been masked.
See the Wiki for information on mesh visibility and creating polygroups:
http://www.pixologic.com/docs/index.php/Group_Visible
Marcus, hi, if you meant drag from the “top” to select the side, then yes that works qite well. Thanks.
spaceboy412, that worked quite well too. It’s debatable which method is better, but they both work quitre well. Thanks.
I think you’re getting the hang of it. 
The Hide/Show Mesh video in the Getting Started>Essentials chapter may also help:
Thanks
I don’t know what is causing these poly’s to be stretched, but I suspect it is coming from either hiding the edge or masking the edge in the previous steps above.
Is there “any” way to fix this at this point as the rest of the model looks great. I just want the stretched area to look rocky like the rest and not stretched?
Your image is missing…
Sorry, It should be there now.
Yes, it’s caused by masking. You could try the Reproject Higher Subdiv button in the Tool>Geometry submenu. Go to the lowest level first, where the polys should be more even.
Thanks Marcus, Yes I tried it and it worked. I can now add the rock texture in that place but the only problem is when I lower the sub-d level to 1 for export my mesh has lost a lot of its initial form/shape and looks like it took a laxative, whereas my mesh was more a cube shape before applying the “Reproject Higher Subdiv” button.
I will have to read what exactly this button does so I can figure out how to keep my mesh at level 1 looking like it did before. I will read up on this , then post an image.
Update:
Interesting. I thought I’d try something for a test. This time I only lowered the Sub-D level to 4 and then applied the “Reproject Higher Subdiv” button. This time I still was able to apply my rock texture to the mesh and it looks good, and when I lower the sub-d level to 1 for export my mesh isn’t as droopy but almost looks like it did before.