Dear unsure,
Follow the below steps:
1. Enter the RMAT command
2. In "Materials" dialog box select the material from list
3. Click on Modify button
4. In "Modify Material" dialog box activate the "Reflection" option
5. Set the Reflection Value on a high value near to 1
6. Activate the "Mirror" check box
7. Activate the "Roughness" option
8. Set the Roughness Value on a high value
9. Click OK
10. Click OK
Farzad
