How to build a beast horn using Maya and detail it in Zbrush
The purpose of this tutorial is to guide you through the process of modeling in Maya. It illustrates some of the modeling techniques used in Maya that some of us might have forgotten about.
Then we are going to export our model to Zbrush for details.
Once the Zbrush phase is done, we are going to export the details as Displacement map and apply it into Maya.
So let’s get started!
download the project files horn_ZB.zip
Modeling in Maya
Create a simple straight line and a circle so it will look something like this
Pick the circle then the line, hit surface – Extrude
You will have a basic cylinder.
The point that I would like to illustrate is the fact you can manipulate the cylinder after it has been created because of the action history.
You’ve got to love that 
Now change the rotation to 360, so we have this nice spiral isoparm — this is what we are looking for.
Right click on the surface — choose Isoparm, and pick any of these spiraled Isoparms.
Choose Edit curve – duplicate surface curves.
Now you can get rid of the cylinder, it served it purpose.
You should have a nice spiraled curve.
Move and scale the circle that we used to create the cylinder and place it so it’s centre is on the first CV of the spiral curve.
TIP: to place it precisely, pick the circle, right click on the curve, and choose control vertices.
Now move the circle while hitting the “V” button or snap to curve
Rotate and adjust so it will look somewhat like this
Pick the circle and the curve and hit delete history to get rid of all the past nodes
Choose Surface, Extrude
In the input channel of the new surface, change the scale to 0.05
Note: You can change the scale to be 0 to have a closed surface but I prefer to do this step towards the end. However, it is up to you.
We need to get this surface ready for Zbrush, so hit Convert – nurbs to poly and open the options window.
Choose Quads (Zbrush only takes quads) and Tessellation methods – control points
Note: You could have done the extrude directly as polygon.
Delete the original surface and rename your new poly to “horn”
Export it as an OBJ file
Note: Zbrush only takes Quads, so keep that in mind every time you export to Zbrush
Open Zbrush and under tools – import, bring your OBJ file horn_ZB.zip
Now you should see the horn in your tools as an icon. Pick and place it in the drawing canvas.
Now before you do anything else, immediately after you placed that OBJ in the canvas,
right click on it and choose edit. Other wise you will be “drawing” more horns.
For more accuracy, hold down the SHIFT button while placing the object on the canvas, so it will rotate on a 90 degree angle.
Now for some housecleaning. I placed my tools and transform menus on the left side of my canvas by clicking on the small circle on the top left of the pull down menu.
Under tools – Geometry, hit divide 5 times
Every time you divide, the poly count will quadruple. In order to see your poly count, move the curser over the OBJ thumbnail in the tool palette.
Now for some sculpting.
First we are going to target the areas that we would like to sculpt. To do so, we are going to mask some areas of the object. You can do this by holding the CTRL button while painting.
You can adjust the brush size by right clicking on the canvas, and it will show you the options for the brush. You can also get the brush options from the top menu.
After a couple of strokes, you should get something like this.
Note: holding the CTRL key while painting will mask; while holding CTRL & ALT will unmask
Then under tools – deformation
Choose inflation and make it 100.
Now we have the base shape.
Unmask all, and let’s get to the fun stuff: “SCULPTING!”
Hold the shift button while you brush on the horn. This will SMOOTH it out for you. Again, adjust the brush size and intensity to your liking, until you get something similar to this.
Use the brush for painting over the horn. To add more deformation to it, experiment with the Zadd, Zsubb, Move, and Smooth brushes
Mine looked something like this.
.
Time for some detaling.
Choose the projection master, and make sure it is for deformation only on one side.
Drop your object.
Now let’s add some scratches to our horn. Once you are done with this side, click on the Projection Master again and pick up your horn.
After a few minutes of painting and sculpting, and using the above tools, you will get something like this. It is now time to export your work.
Again, if you want to know how many polys your object has, just move your cursor on top of the tool menu, and it will give you that information.
The next step is to prepare the model for Maya. When that model goes to Maya, it will be converted to Sub-D or poly smoothed.
So what we need now is the cage model. To do so, we go to Tools – geometry, lower the division to 2, and hit the cage button.
You can delete that first level now by hitting Del lower
Let’s make our UV map. Under tools – textures – AUV tiles, it will make a UV map that has a perfect square for each poly face.
Note: you could have done that step in Maya. Prepare the UV map the way you like it and then when you export your OBJ file it will have the UV done already.
Export the cage OBJ by using Tools – Export. It will save it as OBJ file which has a UV map on it. We will need this in Maya.
Time for displacement and bump maps.
Displacement:
At this level, which is now level 1, of the OBJ cage, go to Tools – Displacement and choose subpix between 2-4. The higher it is, the more accurate your map would be, and the longer it will take to generate. I usually choose 4.
The map size by default, is 1024. I made it 2048 for a more accurate result.
Notice the bar at the top of your screen. It will tell you how long it takes to generate that map.
It will be placed in the alpha tool palate. Highlight it and go to the alpha pull down menu.
Look at the alpha depth factor, mine was 0.9825. We will need that number later in Maya. While we are at it, hit the flip Vertical button.
(That step could be done either in Zbrush, Photoshop or Maya…it’s up to you.)
Hit export, choose tiff format and store it on your HD.
Time for the Bump map.
This is the same thing that we did before, only this time we are doing it at level 3, (it was level 4 before we deleted the lower one.)
Working with Photoshop
Before we start with make sure your Photoshop setting is on ‘No color management’ under
edit > Color setting
set it to Color Management off
Open photoshop and choose Image mode – RGB
The reason we did this, is because maya cannot read Grayscale.
Save your new file and lets call it ‘texture 1′
Image adjustment – Auto contrast
Note: The image we got from Zbrush is gray color. Maya needs a range of black and white to make a proper displacement. I’m not going to get into the details of that , but in a nut shell Maya need a value of Black and White to make a proper Displacement and Zbrush gives a value of gray scale.
Some 3D packages can do it internally. However I could not do it in Maya, so I did it in Photoshop.
Save your new file, and lets call it ‘texture2′
For the bump, convert it to RGB. You do not need to do the auto contrast.
Here is how the Displacment maps I’m going to use look like.
::GFXZoOM |source:highend3d.com::
