The scene above contains balloons that are flying past a window and filling the room with color. This tutorial will show you how to create this caustic balloon effect using a Gobo light filter connected to a spot_light pointing through the window. We will also cover the shading steps used for the balloons. Thanks to Slava Sych for this tutorial.
Lighting
Create a camera and point it towards the window as per the image above. Create a skydome_light and connect a physical_sky to its color attribute. The settings for the Skydome light used in this example are as follows: The settings for the physical_sky used in this example are as follows: Skydome lighting. The window glass is hidden and shadows are disabled for the balloons.Skydome Light
Physical Sky
Spot Light
The settings for the spot_light used in this example are as follows:
Gobo Filter
Connect a gobo filter to the spot_light. The settings for the Noise shader used in this example are as follows: To further adjust the effect you could try inserting a color_correct shader before the noise shader. In this case, the saturation was adjusted to 1.6. Final results for the spot_lightNoise Shader
Final setup for Gobo filter
Shading
Assign a standard_surface to the balloon objects and rename it to BalloonMat. The settings for the Balloon material used in this example are as follows: Create a layerRGBA shader and connect it to the base_color, subsurface_color and subsurface_radius of the BalloonMat. The settings for the color_jitter shader used in this example are as follows: The settings for the Utility shader used in this example are as follows:Balloon Material
LayerRGBA->aiBalloonMat
ColorJitter
Utility