The Five-Minute Ghost Pumpkin! on Renderosity.com

Hello Again Everyone!

This is time for ghouls, ghosts and things that go bump in the night. So, this week I will give you some ideas for your Halloween images. I will begin with a quick modeling of a pumpkin and then some tips on ghost shaders.

Note: the following techniques are specifically for Alias Maya, but they can also be applied to other applications.

Creating The Pumpkin

For the pumpkin I started out with a sphere. As you can see on the image below, it has 32 sections that will make life easer. To create that "creasy look" I select the CVs as shown on the second frame, and then I scaled it down until I get what you see on the third frame. Next, squash it a little to get the pumpkin proportions, as seen on frame four.

In the next image, you can see I have circled two groups of CVs. Select the CVs inside the blue circle and scale down in the Y axis, so you get something similar to what you see on the first frame on the image below. It looks more like a pumpkin but the top section looks too planar. To solve that, select the vertices outside the blue circle (the outer ones), and scale up in the Y axis. Now that the planar look is resolved, you will have a proper pumpkin shape, like the image in frame three.

The pumpkin is finished but we have to make the stem. For that I used a cylinder with 16 sections. To get that irregular appearance of a real pumpkin stem; I moved the CVs in a row, then I gradually scaled down each CV level to get the final look. As you can see the object is hollow so I selected the edge isoparm and used the "planar" command to cap that hole. Now put everything in position and you are done. You can now delete the history if you want.

Ghost Effects

Now, onto the ghost effect � I based the look on Casper as well as the Final Fantasy Spirits, within phantoms. I think that look is better than just printing the whole figure at partial opacity (setting the opacity layer in Photoshop to something other than 100%). To get the Casper look I used a ramp to control the opacity of the material.

Create a ramp and a sampler info node and open the Connection Editor. Use the sampler information as input (left), and the ramp as output (right). Next connect the facing ratio to the ramp U and V coordinates. Just a reminder; black is fully opaque, while white is fully transparent. I used the setting to make the object opaque at the edges, but the gray stripe at the bottom serves to blur the geometry edge.

For the color I used the �brownian1� texture. You can use pretty much anything you want depending on the look you are after. I stuck to the orange color because it's a pumpkin, but if you were to apply this to a character you could very well use a file texture for the skin. Remember that you decide the final look of your characters and objects, so don't be afraid to go wild when creating your textures.

When you are happy with your shader, you can apply it to your object, and click the render button. The next image shows the result after layering the ghost pumpkin on top of an image.

I like to think that the final render is only half way there because I usually like to post-process my images. To get a better ghost effect, you could use different blending modes until you are satisfied with the result. As you can see, the left pumpkin looks horrible when you put it on top of the background. However, the one on the right looks more ethereal, which is what we are striving for.

This is the end of the five-minute pumpkin � if you create an image using the above tips and tricks, please post a link to your gallery images in the comment section below.

Wishing everyone a happy Halloween! Check back for future seasonal mini-tutorials.

Keep Animating!
Sergio

Animation Alley
is a regular featured column
with Renderosity Staff Writer
Sergio Rosa [nemirc].

October 17, 2005

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Member Opinions:

By: deemarie on 10/21/05
Thanks so much for this great tutorial Sergio. These helpful techniques can also be applied to other items for future reference. I can hardly wait until next month ... for the five minute turkey :]

Dee-Marie

By: drifterlee on 10/21/05
I'm new to 3D modeling. What program are you using? It doesn't say anywhere. Is this Max?

By: nemirc on 10/21/05
What turkey? We salvadoreans don't celebrate the turkey day :p

By: nemirc on 10/22/05
I am using Maya ;) I suppose the techniques described here could also be used in MAX (not familiar with MAX NURBS system). However I DID try to make that shader in MAX once and it yielded the same result :)