Modeling And Rigging A Frog
by Erik Ramirez


This tutorial will show you how to construct geometry reference knots for building an animal like a frog, and show the problems that I had to face.

Setting Knots (Rig Creation)

In front view Add>>Armature to create the first link. Go to right view and modify as above and extrude 4 times to create the nek bones and the head. Try to create similar proportions.

Select the second link and [Shift+D key] to duplicate the link and move it to the right side. In front view move it to the right side to create a leg.

Create the leg limb by extruding this bone as above.

Create the fingers by duplicating finger links.

Create the shoulder blade using the same procedure, but now move over the blade area, duplicate the bone to create a clavicle and relocate in to its respective area. Name them Blade_L and Clavicle_L respectively 'Fuse' the clavicle with the blade.

Select the bones shown above and press [Shift+D key] to duplicate the bones. Move them forward.

Align the new bones with the clavicle. Select the arm bone and on the Armature Bones Panel change the parent and select Clavicle_L, then press the connect button to connect it to the clavicle.

Go to pose mode and press M to move the bones to another bone layer. Bak to edit mode [TAB key] and on the Armature Panel [F9] select the next layer where you moved the bones.

Select this bone and press E key to open the specials dialog box and select subdivide.

Now select the frog hand shown above and move it forward.

Move the fingers a little to adjust them.

Create a cube and select the subsurf modifier for it and move it to the frog femur. Select pivot 'bounding box center' and move the vértices to get a primitive shape for wrapping the femur bone. Duplicate the cube to wrap the bottom leg.

Go to pose mode for the armature and parent the cubes to their respective bones. How?. Select objects in this order: Select the femur box and [Shift] select femur bone (pose mode) and [Control+P key] a dialog box displays and select 'parent to bone'. Then select bottom leg box and [Shift] select bottom leg bone and parent. You can see the result in the Frog.blend.

Reverse Engineering

At this moment the knots seem fine, but a frog's living style is frenetic because in evolution the frogs are intermediate between water and ground, then they're excessively dynamic. Hunters and hunted. Their means of defence are their rear limbs as springs always ready to act in danger situations. As the figure shows above, the bak legs don't have enough of a power spring form, the pelvis is quite high, so we must adjust this feature.

Note that as you move the bone pivot positions the boxes adapt to new forms.

Move the bones low enough that the pelvis almost touches the ground for a full crouch.

Subdivide the bone shown and adjust it to get a curved spine. This spine actually acts like spring too, similar to cats when they want to jump high.

The knees perhaps have to be a little high like hoping insects, but these legs are not only for jumping. The form of the boxes doesn't matter now.

The legs have a little problem because they overlap themselves, the Octahedron form helps to see this problem acting as primitive form. The femur and bottom leg are too tight. In top view try to move the knee over a little. I tried to resolve this problem by creating the bone curvature for the femur and bottom leg. The resulting new bones helped me to improve the box forms.

The head seems to be a little big, so let's adjust that.

Modeling the Frog

Continue the last session or open

Frog1.blend Create boxes for other parts of the frog. In top view create a cube and rotate it 45 degrees and adjust the vértices to create the body, add a subsurf modifier to it. Remember to set 'pivot bounding box center' to scale faces and manipulate vertex groups....To get the head, create a cube with a subsurf modifier with levels set to 2 to get the head shape shown above.

When the head form is OK, apply the subsurf modifier to get this form. Apply the subsurf modifier for the body when you are done. You can see the result in Frog2.blend.

Join both meshes, delete some vértices, and then create a bridge to join them into one single mesh. Adjust as needed and attach other shapes like a box for the chest, adjust the head if it is too big. You can see the result in Frog3.blend.

Adjust for frog's head as needed and for smoother results try proportional edit.

Add a UV sphere to main mesh, then add a subsurf modifier. Add some adjustments to the head, that is about half body length.

Add a mouth splitting the mesh and merging some vértices.

Hide the eye sub mesh (H key), and make some adjustments over the ear section (frogs don't have ears, but holes where they can hear).

Add some vértices over the ear area to create a depression.

Adding More Features Finish the model by wrapping more subsurfed boxes to the bones that are left.

Apply a subsurf modifier to this mesh and adjust it to get 3 faces, Extrude them to form the base of the fingers..

Now to create the fingers, go to front view [1 numeric pad] and [Space Bar] Add>>Mesh>>Circle>>6 vertice circle to get a hexagon shape. Add a subsurf modifier to it and scale it a bit to get a finger cross section.

Relocate this shape by positioning the cursor ([Shift+S key] Cursor>>Selection) over the pivot shown above. Select the circle we created and in object mode [Shift+S key] Selection>>Cursor to snap the circle over finger.

With the PIVOT options set to 'Bounding box center' go to Top view and extrude the hexagon forward to create a frog finger, for the knots extrude, position and scale a little, then you must get bak to the original width and finally create a umbrella shape. To close the umbrella, with the latter vértices still selected, [Shift+S] Cursor>>Selection and press E key, then Esc key and W key>> merge>> at cursor or at center or collapse. To get the rear knot you can duplic ate this knot and merge some vértices.

Make the needed adjustments to get this shape for the finger. The tip may be a suction device to stik on walls or something like that. You can see the result in Frog4.blend.

Make several copies of this finger and adapt them to create others.

Make a similar mesh for the rear hand. Actually the frogs have different rear hands that serve as flippers, umbrellas, etc, so in this case I preferred to make my frog reflect that fact, perhaps it is a mutant frog that lives in a bathroom hanging over the walls and ceilings like spiderman. Still, attach each finger to the next mesh to get a single mesh.

Mirroring Limbs

Now, in Front view create a plane mesh at the center. Join each box limb one by one with the plane, select any box and select the plane (object mode) and [Contro l+J key] to join the meshes, select a plane mesh vertex and press L key to select linked vertexes, press P to separate. Next, the next mesh to plane mesh.until complete for all meshes except the body mesh.

This procedure is for moving the center mesh (actually the mesh pivot in object mode) to the center. You can achieve this by [Space Bar]>>transform>>Center Cursor, and [Control+A key]>>Apply scale and rotation, but in the next step we going to mirror these features and we need assure that all meshes have similar relative UCS (Universal Coordinate System).

So when you are done, you can add a mirror modifier to each mesh to get the symmetric part. Select the arm mesh and detach some of the palm mesh in the forehand area. Do the same for the rear hand. You can see the result in Frog5.blend and Frog6.blend. In the Frog6.blend I started to give names to the bones.

Advance Editing

Open Frog7.blend. This file contains the entire armature of the frog. If you take a look you can see why the mirrored bone objects have mirrored editing and how this setting can help a lot in avoiding and correcting errors.

Now, start to apply a mirror modifier to each limb mesh and when the mirrors have been applied, select each mesh again and detach each linked mesh. You can see the result in Frog8.blend.

Oops!!. It seems that the rear hand is actually -the ankle!!?....-If you did all the exercises, select rear hand bone and in edit mode W key to subdivide. Now we have an ankle and a rear hand. Finish by parenting the meshes with their respective bones. You can see the result in Frog9.blend.

Changing Pose

Go to Object Mode for the armature and duplicate it. Move the duplicate to another layer. Select the original armature and on Draw panel [F7] select Wire option.

Go and Select the duplicated armature and enter pose mode. Rotate the femur in Top view and rotate the bottom leg to get this pose. Save your file with another number or name.

[Shift] select the layer where original armature is.

Go to edit mode and select the following bones and move them to where the duplicated bones are. Select the duplicate armature and in pose mode select the bottom leg and [Shift+S key]>>Cursor>>Selection to locate the cursor over knee.

Select the original armature and select the knee pivot in edit mode and [Shift+S key]>>Selection Cursor. The legs will occupy the new position, go to Object mode and un-hide the other layers to see the meshes updated.

You can see the result in Frog10.blend.

When you are happy with the actual pose, you can start to join all the meshes as you wish. You can add extra limbs or more heads to get our era touch. Sometimes I need extra arms too. But, being serious, this model has potential to create other living forms and geometry references by evolving into new structures. A weird method perhaps to create simple geometry but, rather easy?

This model is not finished but it has enough information for you to experiment and improve on your own.