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Combustion 4 Everyone Part 3: G-buffer Builder

Adding depth information to 2D layers By Stephen Schleicher

RPF and RLA data rocks.  It allows you to manipulate a 3D image in a post application to create motion blur, Depth of Field, fog and much more.  But what happens if you forget to render your 3D files with RPF data included?  Before you had to go back and re-render.  With Autodesks combustion 4, you can paint the data in.

Autodesk Media and Entertainments 3dsmax has the ability to save depth information in the RPF format that can be read and used in combustion 4.  Unfortunately, you have to tell 3dsmax to render the RPF data into the file in order for it to be used.  With the new G-buffer Builder feature in combustions latest release, you can build custom RPF files for 2D or 3D images.  Personally, I think the G-buffer Builder is designed with the hard core 3D animator in mind, but in this simple example, you can see how powerful this feature is to even the everyday user. 

Step 1:  In the workspace import a 2D file.  In this example, I created an image in Adobe Photoshop.  This is a flattened image, there are no layers involved.  If you have downloaded the FREE demo version of Autodesk combustion 4, you can play along.

Click for larger image

Step 2:  In this exercise, we will impart Z-buffer (depth) information to the image.  To do this you can use combustion 4s Paint operator to create a gray scale interpretation of the image on another layer.

In the above example, the areas/children that are colored Black are going to be furthest from the combustion 4 virtual camera, while those colored White are closest to the camera.  Shades of gray represent values in between.  In other words, the front row of children is closest, the middle row is next, and the back row is furthest away.

Step 3: Make sure the original color image is selected in the Workspace and apply the G-buffer Builder operator (Operators>3D Post>G-Buffer Builder).

Click for larger image

In the G-Buffer Builder Controls Panel, click on the Z-Buffer button and select the gray scale image you just created.  This tells combustion to interpret the gray scale data as Z-depth information, and apply this information to the color layer.

You are not required to have the grayscale image in the workspace.  When you click on the Z-Buffer button, you can navigate to any directory on your hard drive or network to target a file. This means you can have someone working on creating the buffer files on another system and integrate it into your work without tying up a single machine.

Step 4:  Since we are only dealing with three rows of children, change the Near and Far Z amounts to simplify the controls.  Increase the Near Z to -10 and increase the Far Z to -100.

Step 5:  To the color layer, apply the 3D Depth of Field operator (Operator>3D Post>3D Depth of Field).  In the Controls Panel, change the Size amount to 10, and the Blur Type to Gaussian.  If you drag the Near Focused Plane slider, you will see the children appear to go in and out of focus based on how far they are from the viewer.

When the Near Focused Plane is equal to -10, the front row is in perfect focus.  As the value decreases (becomes more negative), the critical focus plane with shift to the second row, and finally to the third row before going out of focus again.

The Near Focused Plane value can be animated over time to create a realistic rack focus effect. 

This example is just sampling of what can be achieved with the G-Buffer Builder.  When you begin to experiment with creating your own Normal maps, you can take a flat 2D layer and turn it into a believable 3D object for your composition.

Click for much larger image

As soon as I conclude our look at the new features in combustion 4, well revisit the G-buffer Builder and Ill demonstrate more of the cool things you can do to greatly improve your compositions.

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Stephen Schleicher is a well known writer, visual effects artist and media guru! You can see more of Stephen at
www.majorspoilers.com and www.stephenschleicher.com
Related Keywords:combustion, autodesk, discreet, g-buffer, z depth, schleicher, c4, 2d, 3d, rpf, rla

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