In this tutorial, "CG Choice" award winner, Fredi Voss, will teach you how to model and texture a detailed, dead tree trunk, which could be used as a foreground object in a landscape, or even as a stand alone portfolio piece.
This is an intermediate to advanced level tutorial, and not recommended for beginners. The techniques and concepts depicted within are designed to show you how to create the most detailed objects (which would be of a high enough quality to be used in the foreground of a still CG render), and also to demonstrate that several techniques can be combined together to achieve a specific result.
All screenshots were taken from Cinema 4D R11, but it should be possible to apply the hints given here to other releases as well.
Start by creating some splines, but leave some space between them (you will see why later on). You should use "Bezier Splines" here. The angle-limit is normally set to '5 °', but for this project, you need to keep it as long as possible while in the low-poly state.
Now you can start to place the single points of your splines into the third dimension. Select them, and modify their positions. Make sure that the start point of each spline stays on the main spline level. After doing so, your construction should look like this:
Use the splines, in combination with an "n-side" spline, in a "sweep nurb" operation (6 sides on your "n-side" spline should be perfect). The end scale of your "sweep nurb" should be set to around 10 %. You can decide what fits best for your taste, but if you are not sure, just take a look at the structure of tree branches in nature.
You can adjust the individual parameters of the splines to get the form you want. You can also move points, or even add one more branch, but keep in mind that old ,dead, and rotting tree trunks do not have that many branches left. Note: You should also deactivate all of the bottom caps of the smaller branches, as you will not need them later on.
Once you have the general structure looking the way you would like, convert all "sweep nurbs".
Connect all of the converted "sweep nurbs" into one single object. The selection tags created by the caps of each "sweep nurb" can be deleted.
Use the knife tool. In order to be able to merge the single branch segments into one solid form, you need to try to create a good base in your mesh. Note: To make your life easier, you can deactivate the "Visible-Only" option.
Delete the selected polygons as shown here:
Now it's time for you to create polygons. Some of you might think that using the bridge tool would be easier, but the manual production of polys gives you more control over the result. Note: Try to get an organic connection between the trunk and the branches (like in nature). Don't be afraid to create triangles either. In this particular case, they will emphasize the realistic appearance. But remember, no matter what, always keep your mesh clean.
After repeating this procedure at every junction point, you should have something that looks like this:
To get a complete and solid mesh, without separating the polygons or unused points, go into the polygon or point mode, and use the "Select All" and "Optimize" functions. Now you can do a bit more work on the mesh at the bottom cap of the trunk. Note: try to get the impression of a broken piece of wood.
Time for the mighty "hyper nurbs" tool;) A moderate '1-1' setting should do it. In my case this gave me 1877 polygons for the trunk. A '3-3' setting should deliver 24197 polygons, but either way, the result will still look the same.
Use the knife tool again. Switch the "hyper nurbs" setting on or off to get the right interaction. Adding some extra knots will add more realism. Note: Trees in reality are not that smooth. They have a special kind of structure.
Copy and paste the trunk. Now convert the new "nurb" object, and then triangulate it.
Go into the polygon mode. Select and delete random polygons as shown (I switched the trunk underneath to "invisible", to demonstrate the structure more clearly).
Select all of the polygons on the new object, and extrude them.
At this point you should have a very good base for your final object, which is a good time to create a basic light-setup, in order to get a better impression of how your object might work in the final scene.
Now you can start to create textures for your project. I prefer to use image-based textures (most of my image maps are photographs i took on my own for this purpose). You can download the texture files here:
Load the bark image into the color, diffusion ( 50 % strength), and the bump channel. For the sub polygon displacement, use a fusion map consisting of the photograph, and a noise at 500% global size. Note: You can also add a bit of luminance (about 5 %). This will break the ice, and reduce the typical cg-appearance of textures.
Add the texture to the bark. Switch to "Cubic Mapping", and scale it as shown (it is relative to the size of your image map, therefore, i can not give you exact parameters).
A first proof render should deliver something like this:
Create the wood texture by using the map in the color, diffusion, and displacement channels. Similar to the bark, "Cubic Mapping" fits best for this purpose. If you were to use standard "UVW Mapping", it would give you some issues with areas of stretched or squeezed textures. Further more, "Cubic Mapping" gives you more control over the orientation and scale of the image map.
Some more tweaking, and your proof render should look like this:
Now select the bottom area polygons and use "Set Selection". You are going to create some extra texturing...
As a base for the new texture, use the wood texture (that was used for the trunk), and copy and paste it. Now you need to change the displacement map. Use the "centered intensity" mode, for "sub polygon displacement", with a strength of 100%, by 5 meters maximum height. This parameter depends very much on the actual global scale of your mesh, so you might have to change it to a higher or lower setting, in order to get the right effect. Set the parameters of the "hama noise" as shown below.
Now add the new texture to the selection you made before, and scale it as shown.
Create a new render. The base of the trunk now looks less smooth and "polished" than before.
Tweak the bark mesh a bit, by using the "magnet" tool, and working on the edges of the mesh. This will give the impression of the structures that are rotting and falling apart.
Ok, so your little project is almost done:) But something is still missing...
Sometimes, dead trees are covered with a fiber-like substance. I want you to add that here too. Not everybody owns the "Hair Module", so you are going to have to go the old-school way, and use an alpha plane. Use the alpha mask that was provided. Now deform the plane a bit, in order to simulate more volume.
Attach the planes to the model, and scale, flip, and stretch to randomize them. But remember: less is more.
To complete the effect, model some mushrooms, similar to the ones you might find living on rotting wood, and attach them to the dead tree.
Your trunk should now look like this. Note: The whole dead tree scene is 14312 polygons, and the file size is 885 kb. You see, it is not allways necessary to beginn a polygon massacre when you want something detailed in your scene.
I hope you liked my little tutorial.
Cheers, Fredi :)
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