1. Here's why
Freezes and crashes may occur if your Scene is 'too complex' and your hardware isn't powerful enough and/or lacks available System Memory and Virtual Memory.
'Too complex' refers to the following variables:
|A: The number of different models you have added to the Scene.|
|B: The 3D Points number in the top right corner of Build Mode.|
|C: The number and resolution of textures/materials.|
|D: The Movie/Photo Effects you're using, in particular the Sky Light and Hyperlight effects.|
|E: How many Reflection Planes you've added in the Reflection Effect.|
|F: How many Spotlights that are set to Shadows: Dynamic in the Scene.|
|G: How many Spotlights you have selected in the Global Illumination Effect.|
|H: How many large surfaces you have assigned 3D Grass Materials to.|
1.1: To reduce the time it takes to render a Photo or a Clip, you should try to reduce the number of all of the above.
1.2: In addition, please increase the amount of Virtual Memory in Windows:
Knowledge Base article:How do you change the amount of virtual memory in Windows?
1.3: Alternatively, you could consider upgrading your hardware:
Knowledge Base:What kind of computer does Lumion need?
Knowledge Base:Which graphics card do you need?