DataFilterExtension and alpha blending

[richard3d]

I have written a custom LayerExtension that simply outputs a white fragment color (color = vec4(1.0, 1.0, 1.0, 1.0);) in fs:DECKGL_COLOR_FILTER. This extension is added to a layer along with the DataFilterExtension. The filter extension properties are set to fade out dots from a ScatterPlot layer based on a time property. This works until I add my custom extension (the dots are white but do not fade). In this case I want the color from my layer extension (white) but I want the dots to fade based on the DataFilterExtension. The strange part is if I take the color output code and put it in the vertex shader vs:DECKGL_COLOR_FILTER it works as I would expect (white dots that fade over time). However, I am developing an extension that will eventually need to run in the fragment shader so I would like to know what is going on. Thanks in advance!

[richard3d]

After some more digging I discovered the order parameter that can be applied to things like fs:DECKGL_COLOR_FILTER forcing my code to execute after the DataFilterExtension. This then allowed me to modify my final fragment color with the alpha coming from the DataFilterExtension e.g. color = vec4(1.0, 1.0, 1.0, color.a);