Matt/Shadow Composite

In this tutorial we are going to take a look at the Mental Ray Matt/Shadow/Reflection shader. This shader is extremely useful for creating things like endless walls for Studio shots, or for compositing things directly into a photo or video.

What does it actually do? Well it keys out everything except for Shadows and Reflections! no need to worry about those horizon lines ending before your vision anymore, no need to worry about modeling a surface to sit your 3D model on when you wish to composite it into a real photo etc.

You can download the start file for this tutorial along with an image which we will use to composite a 3D model directly into here:http://tutorials.diclementi.com/start_files/mattshadow2_start.zip

When you unzip and open the file in 3D Studio you will find a Light, a Plane, and a sphere sitting on the plane which we will composite into the picture.

I have set up a camera already but in the future you will have to place the plane correctly so that the shadows on the plane look level with the ground in the photo. I have also taken the liberty of setting up the custom size of the render for the render output settings. On the common tab in your Output size you will match the length and width to the same dimensions of the image you are compositing onto. In this case 576pixels by 431 pixels is the image size, so it is also the length and width of the render output.

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Ok now that we covered the basics we can get to work! To begin Open up your Material Editor (M) and your Environment Setup window (8).

We will be transferring textures between the two dialogue windows.

In the environment map channel box.

Click the none button and add a Bitmap, then search for the image you downloaded with the tutorial files.

Then Drag the image you just added over to a new material slot in the Material Editor to change the settings.

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Make sure to change the texture to an Eniron texture, and change the dropdown to Screen.

Then right click on the large button that says Bitmap above it, and select Copy from the menu.

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Then find an empty slot in the Material Editor near your Background image, and click on the Standard button.

Select Matt/Shadow/Reflection from the list under Mental Ray to change the Standard texture to the Matt/Shadow texture.

In the Camera Mapped Background channel box, right click and select Paste (Copy) to add the image on the clipboard to the new Matt/Shadow texture.

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The two slots for the Background and the Matt/Shadow/Reflection texture should now preview to show almost the same thing.

The Image should show up in your Camera's viewport. If it does not simply press Alt+B and change the setting to Use Environment Background.

Now, Assign the Matt/Shadow/Reflection texture from the Material Editor to the Plane in the scene.

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That's it! Just Hit render and marvel at your 3D sphere composited into the Image.

Adjust things like light and shadow via the Light settings in the Modify Tab, texture the sphere the way you like etc.

I hope you enjoyed this one, it works the same way if you load in video or animated backgrounds as well!

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