Written By: Chris
Spline cage modeling is a process that requires the use of 2d shapes, or splines, in order to build a cage that can later be surfaced. This tutorial will show you how to use splines in order to create a shark. Spline modeling take a while to get use to, but is a very valuable skill to have when using organic modeling.
1. Obtain some reference photos
Start by getting some reference photos of your shark. You can usually find some good one online, the key is to find an exact side profile, and if you can, a front profile, of the shark. From looking at my reference image, I created a plane in the left view about the size of the shark. Then I added the image to the plane as a texture. This is going to be used as a reference for obtaining the outline of the shark.
2. Outline the shark using line.
Go to the create panel and choose shapes > splines > line. From the left view, trace the outline of your shark, trying to use as little clicks as possible. Don’t worry if it’s not perfect, you can fix that next. Close the spline by clicking on the first vertex created. Select the line, and under the modifier panel, choose vertices. Select all the vertices in your outline and right-click and choose the option smooth. This will auto smooth the curves between the vertices. Adjust the outline by selecting individual vertices and moving them until you get a desired shape.
3. Setting up the cage.
We are only going to build a cage for one side of the shark and later use symmetry to complete the other half.. This is the hard part. Splines are fairly picky when it comes to how they work. In order to build a spline cage, each spline needs to be attached in order to make a cross-section. This will make more sense soon. Hold shift and the move your spline and make a clone of your outline. Choose attach and click on the other spline to attach them together. Now these shapes are treated as one object. Scale in the new spline so that it is slightly smaller than the original outline. Select the newest spline (you will have to make sure attach is deselected and that you are now under sub-object mode of your spline, remember now it is on object) and make a shift copy of that and scale that down.
4. Using Cross Section and Surface.
Under the modifier panel for your spline, select the option cross section. Start at first outline created and click, then click the second outline create, then the third and then right click. The cross section tool should have built out a cage. The cross section tool works best when the splines are identical. Under the modifier drop down list, select surface. This will add a surface to your cage. If your surface is flipped, choose the flip normals option to flip it to the correct side.
Increasing the patch topology will increase the amount of curve to yoru surface. The number represents how many smaller line between the two vertices make up the curve. Keep this number no grater than 8.
Notice how certain parts of the shark are not surfaced, this is because splines wont have a surface unless the cage is 3 sided or four-sided. This may be better explained in a picture. The green dots are 4 vertices that are connected by 4 lines, They will have a surface. Now look at the blue dots, they do not have lines connecting them and will not surface as there are more than four vertices. In order to create a line, you need to use the create line option under the modifier panel of the spline. Close holes in the cage my creating lines to complete the cage. In order to do this, you need to click from one vertex to another vertex, and right click when done. Think of it as connect the dots. Continue to do this until you have completed the cage. Try to keep the cage as clean as possible, avoiding intersecting lines, and if possible, keep your surfaces four sided as opposed to 3 sided.
To make this process easier, turn on show end result so you can see if the cage surfaces properly . Also, turn on the snap to vertex option by right clicking on snaps toggle button at the top toolbar.
If you cannot select any one the splines, it is because it is not attached as one object, so select attach and click on all your outlines to make sure they are attached.
5. Adjusting the Vertices.
Once you have completed your cage with a surface, you can go back and tweak the vertices by moving them around until you get a shape you like. You will need to adjust the areas around the fins and the tail to create a less boxy shape. Use reference photos to try to get the best accuracy. Go to the modifier panel and select symmetry from the drop down to create the other side of the shark. Make sure you are mirroring the correct axis and adjust the mirror to match the seam. Make any further adjustments to your model and tweaking the vertices to avoid seeing a harsh seem.
If you wish to later add textures and a rig for your shark Once you have tweaked the object, its time to graduate from the spline cage, right click on the object and convert it to an editable poly.