NifSkope Editing

This page will attempt to help users who do not have the advanced programs, like 3D Studio MAX, required to edit NIFs directly. Oblivion uses NIF version 20.0.0.5 while current scripts for free programs like Blender will only take you to 20.0.0.4 (As of 6/10/07). Editing an existing NIF in Nifskope is the best way to achieve working results. One goal of this page is to save people the countless hours of trial and error I had to go through to get edited meshes to work.

Modifying an existing NIF

When modifying a NIF, there are two different beasts to cope with. The first is the NiTriStrips, which set the shape of the mesh that the texture goes over, and the other is the collision data, which tells the game which parts of the mesh players can actually move through. I will demonstrate some of things that can be done in tutorial style with a mesh I recented had to modify, icpalacelibrarystairs01.nif, found in the meshes/architecture/imperialcity/interior directory.

Editng mesh properties en mass

This is quite a detailed mesh, weighing in at almost 1.5 MB, but also very useful, since it is completely surrounded by a some a texture. My goal was to reduce it to just the steps part, and take out the railing, so I could stack one upon the other to make one long stairwell.

The first thing we will edit is the NiTriStrips data. If you are very, very lucky, then the unneeded parts will have separate NiTriStrips. In the first case, we are lucky. if you click on the carpet in Nifskope, you will notice the triangles that make it up will be shown, and the appropriate block will [most of the time] be selected in Nifskope. The block we want is the highest block in the hierarchy that deals only with the carpet. For this reason, I will delete block 39, instead of just 44, since all of the texture data for the carpet is of course not needed. In the Block list, simply right click this block and select block -> Remove_Branch. Remove Branch is needed instead of Remove Block whenever the block has children (can be expanded). Given the ease of this kind of edit, the result is really quite gratifying.

The second thing I want to do is remove that rail. I will use the same process, and delete the whole branch at 20, and not 26. Notice how the other blocks' numbers move up to "fill in" the number gap. Another satisfying edit.

I will leave the flat part at the top even though I don't need it, simply because it would take a long time to remove. However, if you wanted to, I will show you how to remove select vertices and collision vertices in the next mesh.

The final thing to do is to remove the collision data. As you can see, the rail is still highly visible as collision, and will be invisible but impassable to the player. There is not way to select parts of the collision data, so it can be tricky. This particular mesh makes it easy for us though. You will find the collision in box 7, bhkCollisionObject. Most, if not all, meshes use this particular block for starting collision. Expand the entire tree until you reach the bottom, hkPackedNiTriStripsData. This block is the guts of the collision, storing all of the vertices and triangle data. Each vertice is a point in space, and if you expand a triangle, you will notice the first entry includes three numbers, which are the numbers of the vertices that are connected. If you expand the vertices and hold your mouse over the name column, the array index of that vertice will pop up- very useful for fine tuning! Note that without a triangle, the collision vertice itself does not create any collision.

Even though there are thousands of vertices and triangles, there is one way you can do it at once. You can delete these at once from the BOTTOM UP. This is done by changing the Num Triangles and Num Vertices respectively and updating the array (right-click on triangles or vertices and select array -> update). You can add to the arrays, but more useful will be deleting stuff. Lots of stuff. We will start with the triangles. Set the Num Triangles number lower by 100 and update the array. Notice how some of the rail disappears. We are lucky because the rail data was generated last. You will have to experiment to find exactly how much you want off, but for this mesh, the number of triangles I needed was 652, which took out all of the rail data. You can look at the last couple of triangles then to find the very last vertices that are used, and delete those, since they only add ot the file size now. The highest number appears to be 866, so I set the Num Vertices array to 867, and update.

The final step is EXTREMELY IMPORTANT!! Using this mesh will make the game crash completely. I narrowed down the problem to the MOPP data, though I don't even know what it does! inconsistencies will cause the game to crash upon viewing this mesh, so you will have to update this MOPP data. In this mesh, the MOPP Data Size is 21497, and I have no idea how it relates to the collision vertices, so I won't even touch it. The easiest thing to do is to take it out completely. To do this, go to the block one level higher, bhkRigidBody, and change the "shape" reference to the block Italic textafterItalic text the bhkMoppBvTreeShape block, which is number 4- bhkPackedNiTriStripsShape. Doing this removes the bhkMoppBvTreeShape block out of the tree and to the bottom, so you can then cleanly remove it. You now have a useful spiral stairs!