I have a scene, and I need to be able to overlay the scene with translucent polygons (which can be done easily using pygame.gfxdraw.filled_polygon which supports drawing with alpha), but the catch is that the amount of translucency has to fade over a distance (so for example, if the alpha value is 255 at one end of the polygon, then it is 0 at the other end and it blends from 255 to 0 through the polygon). I've implemented drawing shapes with gradients by drawing the gradient and then drawing a mask on top, but I've never come across a situation like this, so I have no clue what to do. I need a solution that can run in real time. Does anyone have any ideas?
It is possible that you have already thought of this and have decided against it, but it would obviously run far better in real time if the polygons were pre-drawn. Presuming there aren't very many different types of polygons, you could even resize them however you need and you would be saving CPU.
Also, assuming that all of the polygons are regular, you could just have several different equilateral triangles with gradients going in various directions on them to produce the necessary shapes.
Another thing you could do is define the polygon you are drawing, than draw an image of a gradient saved on your computer inside that shape.
The final thing you could do is to build your program (or certain, CPU intensive parts of your program) in C or C++. Being compiled and automatically optimized during compiling, these languages are significantly faster than python and better suited to what you are trying to do.
Gradient alpha polygon with pygame