Exporting to Topogun
If you wish to keep working without retopologizing you can do it, but the mesh distribution becomes uncomfortable to work with, and soon you will find you want your sculpting to flow in one direction while the mesh flows in another. I have chosen Topogun to retopologize, but you can use any other software, like ZBrush or 3ds Max (Fig.11).
In order to export the mesh to Topogun we will first decimate it to reduce the polygon count. You can download the Decimation Master plugin directly from Pixologic's web site.
Save your tool before Decimation (If you wish to keep the decimated model save it in a different file).
- From the ZPlugin menu, click on Decimation Master and choose Pre-process Current. Wait for the calculations to be over.
- Choose a decimation percentage of about 10%.
- Click Decimate Current.
- From the Tool menu choose Export and save the model as OBJ.
If you are not familiar with Topogun, it is software which has been specifically developed for retopology. It is much faster than any other similar software because it only has the necessary tools for the job and handles heavy models well. You can download a demo at www.topogun.com to give it a try (Fig.12).
The objective is to create a low poly mesh that will provide a good sculpting base, which means good edge flow and a denser mesh in the places where you will need to add finer detail (face and hands, for example).
One of the big advantages of Topogun is that the geometry you create sticks to the surface of your reference model.
- Open Topogun.
- Choose Load Reference from the File menu.
- Pick the OBJ we have exported from ZBrush.
To navigate, the commands are similar to Maya. Press Alt and drag one of the three mouse buttons to Orbit, Pan and Zoom.
We will be using two modes: Create and Edit. You can alternate between the two modes by pressing the right mouse button. Notice how the cursor changes between an arrow (Edit) and a cross hair (Create).
While in Create mode click on the surface to start creating a vertex on the surface. As you keep clicking you will create vertexes connected by edges. If three or four vertexes get connected by edges in a triangle or quad shape, a polygon is automatically created. When you want to close a shape or indicate that you want to share a vertex, press the Ctrl key while clicking on the vertex (you will notice that the vertex turns red).
If you want to move the vertexes around, just change to Edit mode and move them as it sticks to the surface. To add a vertex at an existing edge, press Shift while clicking at the edge.
As the character is symmetrical, we will only retopologize half of the model.
While creating the vertexes at the center of the body (which is the mirror plane), select those vertexes in Edit mode and from the Modify menu choose ZeroX. This will place the vertexes at the zero X coordinate. It is the only way to guarantee that the vertexes are placed correctly at the center (Fig.13). I have created a keyboard shortcut for this function as it is used a lot (Edit > Keyboard Shortcuts).
- Create the polygons following the anatomical landmarks.
- Make sure to use the ZeroX function to keep the vertexes aligned at the center.
Check Fig.13 to see how the polygons respect the muscle structures. Also avoid creating triangles as quads will divide a lot better and create a more comfortable surface to work with.