Mental Ray Material
Quickly creates shadow for a big site.
This is a really extreme case, but if you work with urban designers this may happen. This is for a big print not for an animation purpose.
If you need to do:
- Render out shadow with alpha for an entire city scene.
- Render size is really big like 5,000pix or higher .
- Clean shadow edge.
- Can’t spend a lot of time.
Using a Render Elements / Shadows, is an easy and quick way to get only shadows from a scene but it is not good for big sized renders because the edges won’t be smooth and clean. If it turns on anti-aliasing, a render time is slow. Also using a matte shadow material for the entire scene, you will get a blank image because the material can receive shadow but no cast shadow. However, we can use a blend shader to resolve this problem.
Step 1 – Make a Blend material
- Material 1 – Arch & Design
- Material 2 – Matte/Shadow/Reflection: Make sure Receive Shadows is turned on and Receive Indirect Illumination options are turned off.
- Mask – Transparency: Input color is white and Transparency color is black.
Step 2 (Render Setup) – Turn on Material Override and drag the material to an empty slot (use instance) then render the scene. I used tiff file format for this.
Step 3 – Render preview is black but if click Display Alpha Channel you will see shadow.
When you bring the image to Photoshop you will see a black image again. The shadow information is under the Channels.
Step 4 – Go to Channels tab and select Alpha 1 (shadow). Select all and copy then paste under the layers tab.
Step 5 – Invert the color then change to a multiply blending mode. You should have nice clean shadow.
Download Material Shadow Element