If your issue is not listed here, contact C Tech support at support@ctech.com.
Blank or black screen after opening a file
The viewer requires WebGL, which is supported by all modern browsers. If you see a blank or black screen:
- Make sure your browser is up to date
- Check that hardware acceleration is enabled in your browser settings (search for “hardware acceleration” in your browser’s settings page)
- Try a different browser — Chrome is recommended
Scene loads slowly or rotation is choppy
Large or complex scenes may need more graphics processing power.
- Close other browser tabs to free up memory
- Try a different browser (Chrome typically offers the best performance)
- On a laptop, make sure it is plugged in — battery saver modes can reduce graphics performance
- Reduce the browser window size — a smaller viewport requires less rendering work
Keyboard shortcuts are not working
- Click inside the viewer window first to make sure it has keyboard focus
- Numpad shortcuts (rotation, zoom, inclination) require a physical numeric keypad — they will not work on compact keyboards or laptops without a numpad
- On some laptops, make sure Num Lock is enabled
Scene file will not open or shows an error
- Verify the file has a
.ctwsor.ctmwsextension and was exported from EVS - If the file was downloaded, make sure the download completed fully — partial downloads will not open
- Try opening the file at viewer.ctech.com to rule out issues with the desktop app
Z Scale looks wrong
The Z Scale (vertical exaggeration) is inherited from the EVS settings when the scene was saved. If objects appear too stretched or squished vertically:
- Adjust the Z Scale slider in Scene Properties
- A Z Scale of 1.0 shows true proportions with no exaggeration
Touch gestures are not working on a tablet
- Make sure you are using a supported browser — Chrome is recommended
- Some older tablets may not support multi-touch gestures for zoom and pan
- See Compatibility for supported devices