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3d studio maxIntermediate Tutorials

Modeling - Trees


Tree Modeling

Techniques and Principles

1.2206 2006 Matthew D'Onofrio Page 1 of 12

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Modeling Trees

Tree Modeling Techniques and Principles

The era of sprites and cylinders-for-trunks has passed and the need forrealistic trees is has become a necessity. Graphics technology has reachedfruition and it's time for the artist to take center stage. This tutorial is here

to bring you, the artist, up to speed by providing a simplified process fromstart to finish.

Setting up the scene

To place a background bitmap, startby selecting the front viewport. Usingthe the main tool bar navigate toViews >> Viewport Background...

The Viewport Background dialogshould appear. At the bottom of thewindow check the boxes for MatchBitmap, Display Background, and Lock Zoom/Pan. Click [ Files... ] andnavigate to your reference image, if you have one. Select the image fileand click [ Open ]. Click [ OK ] toclose the window.

You should now be able to see the

reference image as the backgroundin the front viewport.

By default 3dsmax displaysbackground bitmaps at a very lowresolution. This makes it very difficult to see the background bitmap clearly


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when zooming in.

To fix this first navigate toCustomize >> Preferences from themain tool bar.

In the Preference Settings dialogselect the Viewports tab and click on[ Configure Driver... ] in the DisplayDrivers dialog.

A slightly different dialog will appeardepending on whether 3dsmax is usingOpenGL or DirectX as the primarydisplay driver. If you see a different

window than the one in this tutorial,don't worry. The instructions work the

same for both drivers.

In the Configure Dialog underBackground Texture Size check the

box next to Match Bitmap as Closeas Possible. And under Texel Lookupcheck the box for Linear. Click [ OK ]to close the dialog box once youhave done this.

The reference image placed as abackground bitmap should nowappear much smoother. This makesit easier to distinguish detail when

zooming in closely in the viewport.


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Introduction to splines

Select the create tab in the command panel. Click on the shapes buttonand choose Splines from the drop down menu.

Click the [ Line ] button in the Object Type roll-out. There are two sections that can be see in theCreation Method roll-out: Initial Type and DragType.

The function of a spline is determined by itsInitial Type and Drag Type setting. The firstvertex used when creating a new spline willalways draw a line. Each consecutive vertex'dropped' by clicking once with the left mousebutton will result in the Initial Type. If the theInitial Type is Corner it will draw a straight line;if the type is Smooth then it will draw a smoothline. Drag Type takes effect when you left clickand drag while placing a new vertex. A Drag TypeofCorner will draw a straight line; a type of

Smooth will draw a smooth line, similar to aNURBS CV Curve; a type ofBezier will draw abezier line with a visible manipulator. Thismanipulator can be altered from the the spline'svertex sub-object.

Roughing out the limbs

For modeling trees I recommend using either

Corner/Corner or Corner/Bezier. For the ganglylooking tree seen here I used a combination ofboth.

Begin by building the trunk. If the tree isexceptionally tall or has an odd shape try using


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two or more splines to make up its length and give variation to thecomplete extrusion. Create each branch as a new spline offset from the

trunk or parent branch.

Once you have finished building the rough skeleton of the tree beginshifting the branches and moving vertices in the perspective viewport. It isimportant to reposition the vertices of your branches so they flowrealistically and have depth.

Refining and redefining the limbs

Use this technique to smooth out limbs andbranches if they appear to be too jagged.

Select a spline and navigate to its vertexsub-object in the modifier stack. In theGeometry roll-out click the [ Refine ]button. Click anywhere on the splinebetween two vertices to add a new vertexthat can be moved and repositioned better

continuity.

Detail can be removed in a similar mannerby selecting a vertex and clicking the[ Delete ] button.

Preparing the geometry

To create the surface we will need to first

create the outline of the shape. This outlinewill be extruded along the path marked bythe previously drawn splines.

Make the outline by creating a cylinder anddeleting all the polygons beneath the cap.


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To correct the pivot select the cap object and openthe [ Hierarchy ]tab in the Command Panel.

Realign the pivot by first clicking [ Affect PivotOnly ] and then [ Center to Object ]. Do this forthree cylinder caps with segments of 4, 6, and 7.

Begin cloning the cylinder caps and aligning themat their starting vertex at the base of each spline. Iused caps of seven segments for the trunk, six forthe limbs, and four for the branches.

Extruding the geometry

Select a polygon at the base of a spline. Todemonstrate, I will use the trunk spline.

If you haven't done so already, collapse the cap into an Editable Poly. Todo so, right click on the cap object in the viewport and navigate to ConvertTo: >> Convert to Editable Poly.

Now that the cap is an Editable Poly, navigate to its polygon sub-object.Select all the the polygons of the cap and, in the Edit Polygons roll-out,activate the Extrude AlongSpline dialog( ). Click onthe [ Pick Spline ] button andselect the spline that is baseof the trunk. Apply values toyour extrusion that create aconvincing average for itsshape.

Continue by cloning caps andmaking extrusions for each ofthe remaining splines untilthe whole tree has a surface.


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Multi-part extrusions

For this tree I split the lengthof the trunk into threesplines. One major spline thatspanned the thickest portionof the trunk, a second whereit begins to taper off, and athird completing the length tothe tip. The reason for this isbecause the taper of mosttrees is not uniform. In thiscase, the settings in theextrusion dialog could notaccurately define the shape of theentire trunk.

Use this method to complete anextrusion if part of the tree iscomposed of more than one spline.

To add to an extrusion select the capof the already extruded surface andextrude it again along a new spline byactivating the Extrude Along Splinedialogand picking the next spline inthe sequence.

The final portion of the trunk wasextruded from the cap of the previousspline and optimized by hand at the

wider length to four segments andtapered to three at the tip.


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Smoothing and reducing

With the rough geometry inplace the next step is toremove any unnecessarydetail and smooth out themesh.

In this image to the right Iextruded a very ugly lookingtrunk. Regardless of whatsettings I chose in the dialogthe the cap simply would notextrude smoothly. When thisoccurs choose values thatbring the extrusion as closeas possible to the desired shape in mind. Once the area is blocked outbegin to manually repositioned the vertices and edges until the shapeflows realistically.

There will undoubtedly be

some areas whereunnecessary detail will cropup. This occurs mostcommonly around locationswhere the mesh twists,contorts, or tapers.

The quickest way to optimizethe excess detail is to grabvertices in rings and collapse

them by increasing the weldthreshold. If this welds non-uniformly then it is stillpossible to collapse by hand by selecting two adjacent vertices and clickingthe [ Collapse ]button in the Edit Geometry roll-out.


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Increasing detail as needed

In some instances the resulting mesh may have less detail than desired.The following technique can be used to counter this problem.

In this branch the shape of theextrusion around the bend could usesome improvement. To do so, firstselect the edge you wish to add detailto. In the Edit Geometry roll-out clickthe [ Connect ] button to add a newedge loop to the selection. Oncecreated, the new edges can easily bemoved to add a smother bend to thebranch.

Intersecting branches

When modeling low-poly treesgenerally it's a good idea not to modelthe intersecting joints of branches.This in turn reduces polygon count andeffectively boosts moral among tree


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modelers suffering from sore hands. Keeping the branches as separateelements also makes mapping and repositioning them much easier.

Intersecting branches can be modeled either by physically intersecting thepolygons or snapping the edges to the geometry of the parent limb.

Working with divided branches

The best way to create seamlessintersections for divided branches is byusing snap tools.

To do so, use vertex and edge snap tosnap the vertices of the child branch tothe edges of the parent trunk.

Aligning the edges in this way by handwill yield a smoother transition than ifthe branches were to simply intersect.This also eliminates the need to

perform messy boolean operations.

Smoothing branch transitions

Making a branch actually look like it'sgrowing out of another isn't as obviousas it may seem. Some branches justlook like they're sticking out no matterhow much you move them around.

If this is the case then there probablyisn't enough vertex detail at the baseof the child branch to make it flowsmoothly with its parent. Take this


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limb for example. Simply by adding a vertex to the problem edge andsnapping it to the vertex above smooths out the branch transition perfectly.

Correcting edges

Sometimes 3dsmax's handling ofhidden edges results in a problematicedge. Although the connection of thevertex is fine, the edge is flipped thewrong way around. This can make areally nasty looking polygon thatdoesn't flow with the shape of itsparent.

To fix this error first select the twovertices to connect as the new edge.In the [ Edit Geometry ] roll-out, clickthe [ Connect ] button to connect thetwo vertices and create the new edge.

Once the edge is in place a small bit oftweaking to smooth out the area willgive the branch a much more organiclook


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Conclusion

With all of the techniques demonstrated inthis tutorial you should now be able toeasily construct most any tree regardlessof shape or curvature. I purposefully chosean odd and decrepit tree for instruction toillustrate this very point. Even with all itstwists and turns it was hardly a challenge.

With that said, good luck and happy treemodeling!


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