I am messing around with the sandcastle demo titled ‘Polyline’, trying to incorporate a time attribute for each vertex. The idea being that each vertex can then be conditionally drawn depending upon the current time, which would passed in as a uniform to the fragment shader. This would allow for the polyline to be drawn over time.
Using the PolylineGeometry ‘colors’ option, I am trying to hijack the alpha variable for each vertex to use a time value. I can then customise the fragment shader source to assign an actual alpha based on the value of the hijacked value. I hope that makes sense. Let me know if I haven’t made much sense. My copied code is here http://pastebin.com/hrcjer4y.
The trouble I am having is the ‘colors’ option seems to limit the alpha value to [0,1], setting the alpha value to zero if the hijacked value was greater than one. I was just wondering where it might be happening within Cesium? I have had a look through but can’t seem to identify where this is happening.
If anyone has any suggestions how this could be differently that would also be really appreciated.