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Adding Eyes to Your Character Model

This modeling tutorial is a continuation of the HL2 Custom Character tutorial.

This tutorial covers:
- Preparing a Visual Basic Script to use in XSI to determine positions in the model
- Positioning an eye in the model.
- Determining the position of the center of the eye.
- Adding polygons to the eye holes in the model
- Making clusters of the eye hole polygons
- Adding the eye texture
- UV mapping the eye clusters
- Exporting the model's reference SMD file
- Revising the model's QC file to add "eyeballs"
- Compiling and viewing the model (now with eyes)
- Adjusting the QC file to make the compiled model's eyes appear to move realistically

 

This tutorial may appear to be quite long. However, once you'll worked through it once or twice, you should be able to perform the tasks in just a few minutes. Really!

 
If you worked through the HL2 Custom Character tutorial you ended up with a model with a fairly well textured head.. but no eyes!
In this tutorial, you'll do some work with the model and revise the model's QC file to add eyes which will follow you in a realistic fashion.
 

Prepare the "Position" Script
You'll need to determine the position of the center of the eyeball in XSI and you'll need a script to do that. You don't need to understand scripting to do it.
Copy the script below into a text editor (e.g., Notepad).

' START SCRIPT----------------
'-------------------------------------------------
' Info Position - displays mouse position based on mouse click
' Author: Bruce J. Veazie
' Usage: LMB to get position, RMB to abort.
'
'-------------------------------------------------
info_position

sub info_position

Dim x1,y1,z1,l_button

' Continue looping until we're done
while True
PickPosition "Click position", "Click position", x1, y1, z1, l_button
if l_button = 0 then

exit sub
end if

msgbox "X: "& round(x1, 3) & " Y: "& round(y1,3) & " Z: "& round(z1,3)
wend

end sub
'END SCRIPT------------------------
Save the file as info_positions.vbs in the folder c:\softimage\XSI_4.2_ModTool\Data\XSI_Samples\Scripts\Other.
 

Positioning the Eye
Given the proper information, studiomdl, the SDK Source model compiler, will add working eyes to your model. You don't have to add eyes to the model itself.
However, you need to get that "proper information."
To do that, you'll position an eyeball in the model where you want it and determine it's position to pass on to studiomdl.
Open up XSI and load the scene file you saved at the end of the custom character modeling tutorial.
To make the sphere for the left eye visible, open Explorer and click the l_eye node.
In the main menu, click View->Hide/Unhide Selection to make the sphere for the left eye visible.
Close Explorer. The sphere for the left eye should now be visible, selected and positioned in front of the hole for the model's left eye.
In a Top view, select translate in the Transform panel and select Global and the z axis for translation.
Move the sphere into the model's head until it's just inside the eyelids.
Click the x axis in the translate section of the Transform panel and move the sphere a little to the left.
Change to a Front view.
Click the y axis in the translate section of the Transform panel and move the sphere until it's pretty well centered in the eye hole.
Adjust the position as you like so it appears in a natural position.
 

Determine the Position of the Center of the Eye
To determine the position of the center of the eye, you'll need to load the script you created earlier.
Click on the script editor icon just to the left of the Playback button in the lower left portion of the screen to open the Script Editor.
In the Script Editor, click File->Open..
Select the file info_positions.vbs you saved earlier and leave the Script Editor open.
In a Front view with a wireframe display, zoom in on the sphere.
In the Script Editor, click Run or, with the mouse over the Script Editor, press F5, to run the script.
The mouse point will change to a pen icon. Click the center of the eye sphere.
Write down the X and Y values of the center of the eye.
Click OK to close the message box and right-click to stop the script running.
In a Right view with a wireframe display, run the script and click on the center of the eye sphere to get the z position.
Write down the z value of the center of the eye.
Close the message box, right-click to stop the script and close the Script Editor. You'll use the x, y and z values you've written down later when you edit the model's QC file.
 

Fill in the Left Eye Hole of the Model
When the eyeballs appear in your compiled model, the probably won't fit the eyelids exactly. To fill in the space between the eyeball and the model's eyelids, you'll create a couple of polygon clusters to texture that will give the eye a more natural look.
To work with the model's eyes, you'll need to hide the eye sphere you've been working with.
Open Explorer, click the l_eye node.
In the main menu, click View->Hide and Unselect. Close the Explorer panel.
In a User view with a wireframe display, zoom in on the hole of the left eye.
Use the orbit tool to position the model so you can clearly see all the vertices around the eye.
Click the Object Select button and drag select the model.
Click the Polygon Select button.
In the Model menu, click Modify->Poly. Mesh->Add/Edit Polygon Tool, or press n.
You're going to add CCW triangles to fill the eye hole with polygons. CCW stands for "counter-clockwise." That is, you'll select vertices from the eyelid going around in a counter-clockwise direction to form new triangle polygons.
Above is what you want for the final product. Note that vertices you want to work with are recessed from the outer parts of the eyelids.
The correct vertices can be difficult to select. Use the orbit and pan tools to check your work. Switch from wireframe to shaded displays to get a feeling
Click on the vertex at the corner of the eye and move the mouse to the next vertex to the left.
Click on that vertex and move the mouse pointer to the vertex below it on the lower eyelid.
Right-click to deselect the Add Poly tool and form the new polygon.
Click the last vertex of the polygon you just created and, going CCW (counter-clockwise), make a triangle next to the first one.
Continue around the inside of the eyelids, forming CCW triangles as shown below.
When done correctly, you'll end up with polygons filling the hole in the left eye.
 

Make a Cluster for the Left Eye
When you filled the hole, select the Poly Select tool (if necessary) and click on polygons filling the left eye.
In the main menu, click Edit->Create Cluster, or press ctrl-L to create a cluster of the left eye polygons.
Open Explorer and right-click on one of the operator node names.
Click Freeze to remove the operators from the stack.
Double-click on the Polygon cluster name and change its name in the Property Box to tex_l_eye. Close the property box and close Explorer.
Click on the Select Polygon button and press ctrl-shift-A to ensure all polygons are deselected.
 

Fill in the Right Eye Hole of the Model
Fill in the hole at the right eye of the model in a fashion similar to the left eye.
The vertices you want to work with are at the inner edge of the hole, just as they were for the left eye.
In a User view with a wireframe, zoom in to the hole in the right eye.
Select the Add/Edit Polygon tool, or press n.
Form CCW triangles from the eyelid vertices as you did with the left eye.
 

Make a Cluster for the Right Eye
Select the polygons you just created for the right eye.
Click Edit->Create Cluster, or press ctrl-L.
Open Explorer and rename the new cluster tex_r_eye.
Close the property box and close Explorer but leave the tex_r_eye cluster selected.
 

Adding a Texture to the Right Eye Cluster
With the tex_r_eye cluster still selected, in the main menu, click Render->Get-Texture->Image and click Yes to create a local material.
In the Material property box, click New->New From File..
Navigate to the sourcesdk_content\hl2\materialsrc\SDK\Models\Humans\Male folder in your Steam logon directory and select the image file eyeball_r.tga.
Close the material dialog box.
 

UV Mapping the Right Eye Cluster
Press alt-7 to open the Texture Editor.
You should be familiar with UV mapping after the last tutorial so remap the points for the right eye cluster to take up the entire texture as shown below.
Close the Texture Editor.
 

Adding a Texture to the Left Eye Cluster
Open Explorer and select the tex_l_eye cluster.
With the tex_l_eye cluster selected, in the main menu, click Render->Get-Texture->Image and click Yes to create a local material.
In the Material property box, click New->New From File..
Navigate to the same directory as you did for the right eye texture and select eyeball_l.tga.
Close the material dialog box.
 

UV Mapping the Left Eye Cluster
Press alt-7 to open the Texture Editor.

Remap the left eye cluster points to fill the entire texture.

Note that the reddest portion of the texture is mapped to the inner corner of the eye.
Close the Texture Editor.
Save your scene file.
 

Exporting the model reference SMD file
In XSI, click ValveSource->Export SMD...
Select Model as the File Type.
Click the "..." button and navigate to the sourcesdk_content\hl2\modelsrc\humans_sdk\Male_sdk folder.
Name the file as sdk_custom_male and click OK.
Click OK in the SMDExport property box.
It may take a moment to save generate the file. Be patient. If your screen turns partially white for a moment, that's okay.
Close XSI.
 

Revising the model's QC file to add "eyeballs"
In an ASCII text editor, open the file sdk_custom_male.qc file you created in the tutorial Creating a Custom HL2 Character Using XSI. You should find it, along with the sdk_custom_male.smd file, in the folder sourcesdk_content\hl2\modelsrc\humans_sdk\Male_sdk.
  Note: The coordinates used in XSI are rotated 90 degrees CCW about the X axis from the coordinate system used by the Source engine. The coordinates for the center of the eye in XSI ( x:1.042, y:67.624, z:2.57) translate to (x:1.042, y:-2.57, z:67.624) in the Source engine.

Edit the $attachment "eyes" line in the file as follows to set the attachment point for the eyes:

//------- $attachment edit
$attachment "eyes" "ValveBiped.Bip01_Head1" 0 -2.57 67.624 absolute
//------- $attachment end-edit

The x value is zero (0, zed) because it's the average position of the eyes.

Revise the $model section of the qc file, adding two "eyeball" lines to read as follows:

 

//------- $model edit
$model sdk_custom_male "sdk_custom_male.smd"{
eyeball righteye "ValveBiped.Bip01_Head1" -1.042 -2.57 67.624 "eyeball_r" 1 4 "pupil_r" 0.63
eyeball lefteye "ValveBiped.Bip01_Head1" 1.042 -2.57 67.624 "eyeball_l" 1 -4 "pupil_l" 0.63
$include "../bodyrules_xsi.qci"
}
//-------$model end-edit
Notice that the x coordinate for the right eye is negative (being on the opposite side of the centerline of the model from the left eye).
Notice, also, that the y and z coordinates have been swapped to reflect the orientation of the axes in the Source engine.
Save the file as sdk_custom_male.qc in the sourcesdk_content\hl2\modelsrc\humans_sdk\Male_sdk folder.
Keep the text editor open. You'll probably need to adjust the position of the eyes by editing the file.
 

Compiling the Model and Adjusting the Eyes
Drag-and-drop the sdk_custom_male.qc file onto your studiomdl desktop shortcut.
A command prompt window will open up and studiomdl will compile the file. It may take a minute to compile. Wait for the command prompt window to close.
Open the Half-Life Model Viewer (HLMV) from your Source SDK launcher.
In the HLMV, click File->Load Model.. and naviagate to the models\sdk\Humans folder and double-click on sdk_custom_male.mdl.
Ideally, the eyes should look straight at you and follow you as you rotate the model.
As shown above, the eyes are too high in the sockets, indicating the z value of the eyeball location should be decreased.
If the eyes in your model appear to be too low, the z value should be increased, instead.
Edit the qc file and change the value 67.624 to 67.5 in both the "eyeball" lines. If you need to increase that value, change the value by a small increment to 67.7 or so.
Save the qc file and recompile the model by dragging-and-dropping the edited file onto your studiomdl desktop shortcut.
View the change in the HLMV. If you still have it open, click File->Refresh or press F5.
That's more natural looking.
If you desire, make small adjustments in the z value in the qc file, recompile and view your model until you're satisfied.
When the vertical alignment appears to be satisfactory, rotate the model to the right and left.
As shown above, the eyes rotate too far to the model's left side when it's rotated to its right, indicating that the y value needs to decreased.
Edit the qc file to change the y values to -2.71 (remember, decreasing a negative value makes it more negative).
By playing around, adjusting the values and recompiling, I arrived at values of x: 1.042, y: -2.71, and z: 67.5 for a fairly natural movement of the eyes.
 

You now have a HL2 model which you can customize.
By using the Male_06 model as a base for your sdk_custom_male model, it comes with all the animations that Valve has already figured out. You can add additional custom animations by following the steps in the tutorial Create a Custom Sequence for the SDK Model.
Things you may want to try now are: create a cluster of the upper body polygons and apply a custom shirt or tunic texture or add more polygons to the shoulders and arms for a more realistic upper body.
Learn more about weightmapping to make adjustments in the arm and leg vertices for more realistic movement.
Experiment with your custom model and have fun!

 


updated 22-Sept-2005