Modeling with Soft Bodies

On January 26, 2008, in Tutorials, by Admin
This tutorial will show you how to use soft bodies to create a static model. Here we have
an old style fruit stand. I want to create a realistic looking canopy for it however, I don’t
want to have to try and model the different folds and shapes of a canopy. I’m going to create
a soft body grid and let it do all the work for me.
I’m going to place my 3D cursor in the approximate location I’ll want the grid to start in.
Switch to over head view with 7 on the num pad.
Press space bar, add, mesh and grid.
We’ll go with the default dimensions of 32 x 32 for now.
Next, we’re going to UV map and texture our model first, which will make that process much easier.
From the overhead view, select your model and press F to create a new UV map.
Select all of your faces then press U to bring up the UV Unwrapping options. Select
project from view to create a simple map.
From a UV/Image Editor window, select all of your faces and click Image, Open to load the
texture you would like to use. Adjust the map until your happy with the results.
For more help with textures, refer to my tutorial on Materials.
Here’s a test render so far.
Next, we’re going to define our soft body. From edit mode, select all of your vertices. We’re going
to create a vertex group for our soft body.
Under Vertex Groups in the Links and Materials tab, click the new button to create a new
vertex group.
I decided to name the group, Canopy. You can enter it in this box.
Change the weight to 0.000 and click the Assign button. This will assign all of the vertices
to this group with a weight of 0. A value of zero will cause a vertex to fall when it’s in a soft body.
A value of 1 for a vertex weight will prevent the vertex from moving. Values in between will cause a vertex
to fall for a different distance.
Click the Objects and Physics buttons. Locate the Soft Bodies tab.
With your canopy selected, click the Soft Body button.
Next to the Use Goal button there’s an up and down arrow. Click this and locate the name of your
vertex group. In my case, I named it Canopy.
Switching to a side view, I’m going to move my grid a little closer to it’s final location. I’ll line it up
so that it’s resting on top of my horizontal supports of my fruit stand.
Next, I’m going to select some vertices that I don’t want to move. I’m going to select the ones directly above the
horizontal supports.
Going back to the Links and Materials tab, I’m going to change the weight value to 1 and click
Assign again. This will re-assign the vertices to the same group, only this time with a value of 1.
A value of 1 will cause the vertices not to move when we begin the soft bodies.
Back to Soft Bodies, look for the Soft Bodies Collision tab. With your canopy selected, turn on the
Self Collision button. This will cause the canopy to bounce off of itself when we start
the simulation.
Under the Soft Bodies tab, turn on the Bake Settings button. You can adjust the end frame here.
Were going to bake the simulation. This way will be able to flip through the various frames that are
created without having to run the simulation every time.
The frame selector is shown here, currently showing Frame number 27 as the current frame.
Here’s the first attempt. I’m not real happy with it. It looks like my customers will
hit their heads while looking at the fruit. I’m going to go back and make some adjustments.
Here’s a test render. Yes, definitely too droopy. Let’s tighten it up some.
Under the Soft Bodies tab.. within the Bake Settings.. there’s a button labeled Free Bake.
Click this to clear the simulation so we can make some adjustments.
I’m back in edit mode here. This time, I’m going to select these vertices and give them
a weight value of 1 so they won’t move during the Soft Body simulation. Let’s see how
that looks.
Under the Links and Materials tab, with the weight value set at 1, re-assign these vertices
back to the group with a value of 1 so they won’t move. Click the Assign button.
Baking the Soft Body again and quick test render.That’s better. A little too rigid looking now. Let’s try to find a happy medium. Plus,
I think I’ll trim off the leading edge of my canopy a bit. I’ll cut a few rows of vertices off of
the front.
Let’s give these a weight value of 0 and re-assign them to the vertex group.
Back to the Soft Body tab, I’ll adjust the Mass and Speed settings down a bit. Making
the canopy lighter and slower.
After baking the simulation again, flipping through some of the frames, I find one that I’m
happy with. I’m going to save this as my static model. I’ve also turned on Sub-Surface to give
my model some finer details.
With your canopy selected, open a scripts window. Select Scripts, Export and Wavefront (OBJ).
Enter a name for your object and just click OK for all of the default settings when the options
window opens up.
Now we’re ready to reload our model as a static mesh, free of the soft body simulation.
From the Scripts window, select Scripts, Import and Wavefront (OBJ).
Locate your model.
Click OK for the default options that open up.
You model will load right on top of your existing one. Here I’ve slid my new object over to
the left for the moment.
Here’s a quick test render. My original model to the left, still has the soft body simulation
applied to it. Trying to edit it will free the simulation and cause it to go back to it’s
original shape, a flat grid. My new model to the right, reloaded, will stay in its current shape.
I’ll just need to turn on Smoothing for the new object and re-adjust my texture so it’s 2 sided again.
I moved my original model to a hidden layer for now. I’m going to move the new model back
in place over the fruit stand.
Here’s my new static object. Not too bad. I’ve used this trick to model other things like
flags, banners or clothes.
Good luck with your modeling.
Scott
 

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