Saturday 22nd Mar 2014

This is Part 1 of my tree building tutorial. you can access the other parts from the bottom of the page.

Creating the trunk

Firstly you’ll need to get your reference image into 3DS Max. Start by creating a plane, use the pixel dimensions of your image to get the correct ratio. Then map the image to the plane and put it a little way back from the central plane. To avoid accidently selecting the wrong object you should freeze the reference plane, so right click the plane and untick ‘show frozen in grey’. Now freeze the plane and you’ll still be able to see the image.

Start by creating a spline for the trunk. Start at the base of the tree and work your way up the length, adding control verts at the key points. Now create a circle shape and with the trunk spline selected press create -> compound objects -> loft. Under the loft options hit ‘get shape’ and select your circle, the circle will now form the profile of your tree trunk.

01 Modelling the Tree

To make the poly modelling easier we’re going to restrict the amount of Shape Steps around the trunk to be 2. This should result in 12 subdivisions around the trunk. We’re doing this as numbers evenly divisible by 4 are going to make joining branches much easier later on. To keep the polygon count down also set Path Steps to be 1, we can always add loops as we need them.

02 skin steps

Now we’ll taper the trunk along the length. With the trunk selected go to the modify panel and scroll down to the bottom of your loft options. Select the Scale button inside the Deformations roll out, by adding a few extra control points and creating a sloping graph you can control the width of the trunk over the height of the tree.

Note: Don’t let the scale drop entirely to 0 at the end of the trunk, keep it just slightly open. We’ll patch this hole up later on.

Also ensure that you come around to the side view and move some of the spline control verts a little tocreate a sense of sculpture in this direction as well. An entirely flat tree isn’t going to look very natural.

03 Deform the Loft

 Creating the branches

Now start creating the branches in the same manner. But for the branches set the Shape steps to be 1 which should result in 8 subdivisions around the surface of the branch. Again this will make blending everything together much easier

04 Secondary Branches

Also ensure that you untick ‘Cap Start’ and ‘Cap End’ for the branches, we’ll leave them open for now.

Repeat this process till you get all the branches in place

Switch to the top view and rotate the branches around a little so they create much more of a 3D form (you can shift their pivot points to the centre of the trunk to make this easier). Even though all my branches are based on the same circle I’ve managed to make them slightly different widths using the Scale Deformation in the skin parameters.

You’ll notice that I started to deviate a little from my design, this was as a started to rotate branches around the trunk to create a more 3D form.

05 Secondary Branches Layout

Once all your branches are created and placed you’ll want to start blending them into the trunk. Select the trunk, then under the Edit Poly modifier press attach and select a branch. If you capped the branches delete the cap at the base. Now select two edges on the trunk where you want the branch to connect (you might need to create a new edge loop using connect if there’s nothing nearby).

06 Secondary Branches Blending

Chamfer the edges, delete the faces that are created and ensure that the two corner verts are welded as shown below.

07 Secondary Branches Blending

Now with the border edges of both the hole in the trunk and the end of the branch selected, press bridge to connect them together.

08 Secondary Branches Blending

09 Secondary Branches Blending

And that’s pretty much it for each branch, repeat this process until all your branches are connected to the trunk. This video shows the process in more detail.

Creating the secondary branches

Once all the Branches are blended we’ll create the Secondary Branches. I use the Branches tool found in Graphite tools -> Freeform. This allows you to sculpt out a branch created from a series of extrusions from a face. With the tool selected, select a face and draw the shape required. It takes a little practice to use this tool, but with a little patience it’s a great way to create these branches.

10 Secondary Branches Extruding

11 Secondary Branches Extruding

If you end up with too many subdivisions then open up the options for the Branches tool and set the minimum distance to a slightly higher value to prevent the tool from creating too many subdivisions along the length of the new branch.

Keep checking the top view to ensure you’re filling in the volume. These secondary branches should help fill out the 3D form.

12 Secondary Branches Extruding

This video shows the process of creating the secondary branches

 Splitting the ends of branches

Some of the branches look a little fat and need to split at the ends. To achieve this trim off a couple of loops from the end. Then Cap the border edge and end use Cut to split it into two equal quad faces. Now use the Branch tool to draw in a fork shape.

 13 Splitting Branches

14 Splitting Branches

This video shows the process of splitting the ends of the branches

All that remains to be modeled is the top of the tree. I chose to split the trunk in two to create two branches. This video shows the process of splitting and capping the top of the tree

Finding and fixing Triangles and N-Gons

To ensure there’s no Triangles or N-Gons use the ‘By Numeric’ tool found in the Graphite Selection tools. This will select any faces over, under or equal to a certain value. I set the value to 4, selected the ‘more than’ symbol and then hit the arrow to select all faces with over 4 edges. You can now work your way around the model and turn these faces into quads, you’ll also want to find and fix any triangles by choosing the ‘less than’ symbol and the arrow icon to select all the triangular faces.

15 Fixing NGons

16 Fixing NGons

This video shows the process of finding and fixing Triangles and N-Gons

Capping and closing border edges at the ends of the branches

Now it’s time to go hunting for border edges and cap them. To do this switch to ‘Border Edges’ Sub-Objects and then select all. Now deselect the base of the trunk and then zoom to selection to hunt down open branches. For each edge you find, collapse the border edge down and then delete every other edge heading toward this point so that you end up with quads only

17 Capping Border Edges

18 Capping Border Edges

19 Capping Border Edges

20 Capping Border Edges

This video shows the process of capping and closing border edges

Wrapping up

You should now have a rough polygonal tree that looks a little like this:

21 Tree Model

Hopefully now you should understand why we started with 12 subdivisions around the trunk, then 8 for the branches and finally 4 for the secondary branches. By keeping everything in multiples of 4 it’s easy to keep our mesh as quads. This is extremely important in a mesh that’s going to be sent over to Mudbox for sculpting.

It’s also worth noting that I made a couple of errors with this mesh. You can see in the image that the polygons half way up the trunk surrounding that first branch are long and thin. This causes issues in Mudbox as it prefers fairly square polygons, very thin polys can cause some issues. I only noticed the error once I was quite far into the sculpt but you can avoid these issues by adding an extra loop just above and below this branch.

We could unwrap this tree before sending it over to Mudbox. However more than likely we’ll end up making some changes to shape while sculpting. I changed the tree a lot once I was in Mudbox as my 3DS Max mesh was looking a little wobbly and undefined. So it’s safest to unwrap after the sculpting is complete to prevent any UVW stretching. We’ll come back to this once the sculpt is complete.

Before exporting into Mudbox put the tree back at the origin and the reset xform tool. Sculpting off centre can cause issues in Mudbox.

In the next part we’ll bring the mesh into Mudbox and start tightening up the shape and get some detail onto the tree.

Jump to other sections:


Part 1 – Polygon modelling

Part 2 – Mudbox sculpting

Part 3 – UV unwrapping

Part 4 – Texturing in Mudbox

Part 5 – Baking to a low resolution mesh

Part 6 – Adding leaves and finishing up