Spring Foliage

Ted Boardman tedb@tbmax.com         http://www.tbmax.com


Well, spring is actually coming to the seacoast of New Hampshire. Most of the snow is gone from my back yard and a crocus or two have popped out in a flash of color.

With spring being a time for foliage, we may as well take a look at a quick method I use to create relatively low polygon foliage that looks fine in the distance and from directly above and casts inexpensive shadows.

There is no shortage of options to generate foliage for indoor and outdoor scenes in 3ds max or VIZ, but they always require a compromise. These trees and shrubs are no different, but do offer another alternative that can be used alone or mixed with other mapped or modeled for a wider variation of foliage in your scene. New foliage can be created in a matter of minutes and require no plug-ins. Remember, the keyword here is efficiency and flexibility.

Here are two images showing some typical foliage used in a couple of scenes in which I was copying two watercolor paintings I had seen recently. The tree in the street image on the left and several of the deciduous and fir trees in the stream image on the right of Figure 1 were created in several minutes. As a side note, the street scene was done in 7 hours and the stream scene was done in 5 hours, mostly as exercises in EditablePoly modeling in max 5.

Figure 1: Low polygon deciduous and fir trees used in two scenes.

Generic Deciduous Trees

This tree will initially be made of two objects, the trunk and the foliage. These two objects will then be attached with the option of creating a Multi/Sub-object material from the separate materials for the trunk and the leaves.

I’ll run through the fundamental process for both the modeling and the materials, keeping in mind that efficiency is paramount. If you need realistic trees, then you’re better off with one of the third party packages that will generate them.

I’ll create these examples in VIZ 4 and have Jeff post them on cgarchitect so they may be loaded in either VIZ or max if you want to view them more closely. In max 5 the Editable Poly tools are slightly different, but function the same.

I’ll just walk you through the steps I use to make the trunk and I recommend that you re-create your own examples using any variations that fit your needs.

The trunk starts with a Cylinder primitive 1 foot in Radius, 12 feet in Height, 12 Height Segments, 5 Sides, and Smooth turned off. I then right-click on the Perspective label and enable Edged Faces. I then right-click on the object and choose Convert to Editable Poly. Name this object Trunk

Hit the F2 key to turn on Shade Selected Faces. In the Modify panel, go to Polygon sub-object mode and select a polygon about 2/3 of the way up the trunk. In the Edit Geometry rollout, click the Bevel button, pick on the select polygon and drag a branch with a slight bevel taper. Repeat to make another segment to the branch. At Vertex level move the vertices to make a branch. See Figure 2.

Figure 2: Use sub-object Polygon Bevel and sub-object Vertex mode to create a branch.

Repeat the last process to make two more branches higher up the trunk. In Vertex sub-object mode, move vertices near the base to flare the base out somewhat. You may need to select vertices in one viewport and move in another to see what you are doing. See Figure 3 for the results.

Figure 3: Create two more branches and flare the base of the trunk somewhat.

Exit sub-object mode and, in the Surface Properties rollout, check the Use NURMS Subdivision option. Increase the Iterations to 1. This adds polygons and rounds the tree for a more organic look. See Figure 4.

Figure 4: Use Editable Poly’s built-in NURMS Subdivision with an Iteration of 1 for a more organic trunk.

The trunk is now reasonable looking, but if you right-click on it and look in Properties you will see that it has 86 faces (in my example). Right-click on the trunk and choose Convert to Editable Mesh. Check the faces count again and you will see it is actually 692 faces. This is the number of faces the renderer will see. While that may not seem like a lot, by the time you create a forest it could have a significant effect on your render times.

Select the trunk and, in Modify panel, Modifier List, choose Optimize modifier. In the Parameters rollout enter 12 in the Face Thresh: field. This drops the count to 352 without destroying the form of the trunk. Right-click and Convert to Editable Mesh again. You can reduce more faces by deleting the bottom faces at the base of the trunk, in my case another 22 faces for a total of 330. Your trunk may be different but you get the picture.

The foliage is created with a series of steps in which you first create a canopy, then scatter very simple triangle “leaves” over the surface. It is important to keep in mind how the Scatter compound object functions. You pick an object to use as distribution object which generates a new clone of the mesh over which the actual leaf object is spread. You must both hide the distribution clone and delete the original distribution object to be able to see through the leaves.

The Canopy

I started here by creating three Geosphere primitives that I positioned around the trunk to simulate a canopy of leave. I then convert one of the Geospheres to EditableMesh and Attach the others to it, for a single object. See Figure 5.

Figure 5: Create Geospheres and attach them together as a single mesh to use as a canopy for the tree.

To create less of a regular “lollypop” form, I apply a Noise modifier with 5’0” in each Strength field and 40 in the Scale field. Note that for Noise to affect objects, the object must have sufficient vertices and the Scale number must usually be lowered from the default 100. See Figure 6.

Figure 6: Attached Geospheres with Noise modifier to “randomize” the canopy.

At this point I usually convert the canopy to EditableMesh, but that is optional. The shape and size of the canopy is, of course, dependant on the type of tree you are trying to represent. Sometimes I will use several separate objects clustered around the branches that may or not be somewhat flat, or I might use a tall conical object to start.

The Leaf

Here I’ll start with a single leaf that will have a material applied. The leaf is created from an Ngon shape with 3 sides and a radius of 8 inches.

Note: The most important point here is that the shape is created near the base of the tree. There is a relationship between the pivot point of the leaf and the surface that it will be scattered on. If the pivot points are too far from each other an offset from the surface can develop and the leaves will be far from the canopy.

Select the shape, right-click on it to convert it to EditableMesh. This creates a single face surface with no thickness.

The Leaf Material

In the Material Editor, change a Sample Window from Standard to Double-Sided material type. See Figure 7. You can “Keep the Old Material as Sub-Material”.

Figure 7: A Double-Sided material applies two materials to a surface based on the Face Normals.

Note: this is not the same as a 2-sided material. Double-Sided materials contain two materials, one applied to the side of a face with the Face Normal and another that is applied to the backside of the face. This allows much more flexibility in how the leaves look. The effect must be rendered to be seen as only the first material will show in the viewports.

Set the Diffuse color to a light green in the first material and an orange in the second material Diffuse color. This will enable you to see the effect and you will make more adjustments later. Assign this material to the leaf object you have just created.

Scattering the Leaf on the Canopy

Select the triangular leaf object at the base of the trunk. In the Create, Geometry menu, drop below Standard Primitives to Compound Objects. Click the Scatter button.

In the Pick Distribution Object rollout, click the button of the same name. In a viewport, pick on the canopy object. The color of the canopy will appear to change, but that is just the new distribution object being created. There is also one leaf applied to the new object.

In the Scatter Objects rollout, enter 1000 in the Duplicates field and you will see 1000 of your triangular faces randomly scattered over the surface. It is actually the pivot point of the leaf that is on the surface.

In the Display rollout, check the Hide Distribution Object option. In a viewport, select the Geosphere canopy and delete it, you no longer need it. You will, however, still be able to adjust the number of leaves scattered.

Render the scene. If you have a ground plane and a shadow casting light you will see something similar to Figure 8. The tree appears as you would suspect, triangles randomly surrounding a trunk. You will fix that.

Figure 8: The tree so far with a ground plane and shadow casting light. The leaves are clearly triangles and not very convincing, yet.

In the Scatter Object rollout, enter 10 in the Vertex Chaos field. This randomly moves the vertices of each triangle to make a more irregular pattern. See Figure 9. There are also controls in the Transform rollout that will increase the randomness of the placement and size of triangles.

Figure 9: Increasing the Vertex Chaos setting will make the leaves more random in size. You also have controls in the Transform rollout for this purpose.

Adjusting the Material

The severely triangular nature of the scatter leaves won’t convince even the most forgiving client. You will next apply a very strong bump map to each material to detract from the visibility of the edges of the triangles.

In the Material Editor, enter 300 in the Bump Amount field and apply a Noise map to the Bump slot of the first material in the Double-Sided material. In the Noise Parameters rollout, set the Size of the map to 3. Enter 0.8 in the High Threshold and 0.2 in the Low Threshold fields for a more contrasting Noise map. Using the Material/Map Browser you can now drag and drop this map into the Bump map slot of the second material in the Double-Sided material. Use the Instance option. Also, remember to set the second material’s Bump Amount to 300.

Render the scene and the leaves will have a much more random chaotic look. See Figure 10.

Figure 10: Applying a very strong Bump map to both the Double-Sided material levels will detract from the noticeable edges of the triangular leaves.

Once you have finished adjusting the leaf count and placement, it is a good idea to convert the leaves to an Editable Mesh object to reduce the overhead of the Scatter operation.

Create and assign a new material for the tree trunk. Here, I’ve used a simple Noise map in the Diffuse color and the Bump slot.

Finally Attach the leaf canopy and the trunk into a single tree with a descriptive name. Choose the default Match Material ID’s to Material option.

In the Material Editor, activate an empty Sample Window and use the eyedropper button to pick the material from the new tree object. It will become a Multi/Sub-object material automatically.

The tree is by no means finished; you must experiment with materials to get the best illusion of leaves for your needs. Try experimenting with Falloff maps in the Diffuse color slot and adjusting the Specular highlights, for example, to create a more convincing look in your scene. Right-clicking on the tree and going to Properties reveals a total of 1330 faces for this tree, a very good start for a tree that casts shadows and can be viewed from above.

Generic Fir Tree

The general principles used in creating a fir tree for use in your scenes are similar to the deciduous trees, simple geometry and random materials.

The trunk can be a simple cone with 5 sides, 1 height segment, and 20 feet high, for example. A single bough is a flat plane 4 feet in length and 8 feet in width that has been converted to Editable mesh and has the outer end corners welded to the end center vertices to form 4 triangular faces. The center vertices have been moved toward the outer end. See Figure 11.

Figure 11: Start with a Plane 4 feet by 8 feet, convert to Editable Mesh and use Target weld to weld the outer end corners to the end center vertices. Move the center 3 vertices to about 2/3 of the way to the end of the plane.

Use the Align tool to align the left center of the plane with the right center of the trunk.

Go to Hierarchy panel, Affect Pivot Only, and use the Align tool to align the Pivot of the bough to the center of the base of the trunk. See Figure 12.

Figure 12: Align the Plane to the center edge of the trunk and the Planes Pivot to the center of the trunk base.

Raise the 3 center vertices of the Plane similar to Figure 13. I used 2 ½ feet for the vertex close to the trunk and 1 foot for the two outer vertices.

Figure 13: Raise the center vertices of the plane to create a bough that “hangs” off the trunk and touches the ground.

In the Top viewport, hold the Shift key and rotate the plane 36 degrees in the Z-axis. Create 9 copies of the bough to surround the base of the tree. See Figure 14. Use the Attach function to attach all the planes into a single object and apply the leaf material from the previous exercise. Assign the Trunk material to the trunk.

Figure 14: Rotate the plane 36 degrees in the Z-axis and make 9 copies. Attach all the planes into a single object.

With the new bough object selected in the Top viewport, go to Tools, Array. Enter 2’0” in the Z-axis Incremental Move field. Enter 18 in the Z-axis Rotate field. Enter 80 in the X and Y Scale and 90 in the Z Scale fields. The rest of the default are fine for this example. See Figure 15.

Figure 15: Use the powerful Array tool to copy, rotate, and scale in one action for a cone shaped array of boughs.

Attach all the boughs and the trunk into a single tree and you have a reasonable fir tree of only 420 faces. See Figure 16. You will, of course want to adjust the materials for a more convincing coloration and bump pattern, but this exercise should give you a start.

Figure 16: A deciduous tree with 1330 faces and a fir tree with 420 faces can efficiently fill the background areas of your scene with foliage.

You could try applying a Noise modifier to the fir tree to randomize it further.

Summary
Again, the sole purpose of this column is to get you started on creating trees that can be used as filler in a scene. The advantages are that they are very low polygon, they cast shadows, and can be viewed from above. The disadvantage is that they look like crap when viewed close up.

Adjusting the materials will give you a wide variety of looks and, with a little practice you can create new trees in a matter of minutes. Try creating hedges and shrubs with this same technique, just leave out the trunks.

These trees can be mixed in a scene with other, more complex trees, again as filler to make a fuller forest landscape.

Use the Scatter tool to randomly place these trees over a landscape surface, as well. The Proxy option of Scatter will allow you to have complex forests that are fast in the viewports as they show as simple pyramids and only as trees at render time.

The leaves of the deciduous tree could be mapped with a leaf image with opacity, but my experiments have shown this not to be cost effective as the time required to calculate multiple levels of opacity can be slow and the look is just not much better. Go for one of the commercial third party options if these simple trees don’t meet you needs.

Good luck and have fun.

Ted