Is there a way to make a radial mask (spotlight) using filters or blends?

Solar2D Advanced Graphics
#1

Think of a find-in-the-dark-using-spotlight puzzle. There is an image, on top an opaque black rectangle, and on top a radial spotlight that allows to see through the black rectangle.

One way to achieve this effect is with graphics.newMask(). But that requires preparing a file. Is there another way to do this using the new filters/blends/snapshots/something else ?

What if the spotlight must have a gradient alpha?

#2

Totally possible. I accomplished this by using porter/duff blend modes. You can take a look at the source code I posted here: http://forums.coronalabs.com/topic/41510-2-demos-for-the-contest/ I used images because I had some performance issues when using 10-20 spotlights but you could use circles with the generator.radialGradient fill effect.

Basically you are looking for this code:

--inside swcaster/engine.lua snapshotMask     = display.newSnapshot(engine, width, height) local r = display.newRect(snapshotMask.group, 0, 0, width, height) r:setFillColor(0, 1) --and then swcaster/light.lua function \_createMask()         local m = display.newImageRect("img/lightMask.png", 256, 256) -- this image is inserted in the mask snapshot group         m.blendMode = "dstOut"         return m end  

Hope it helps.

Ivan.

#3

Thank you, Ivan!

#4

Totally possible. I accomplished this by using porter/duff blend modes. You can take a look at the source code I posted here: http://forums.coronalabs.com/topic/41510-2-demos-for-the-contest/ I used images because I had some performance issues when using 10-20 spotlights but you could use circles with the generator.radialGradient fill effect.

Basically you are looking for this code:

--inside swcaster/engine.lua snapshotMask     = display.newSnapshot(engine, width, height) local r = display.newRect(snapshotMask.group, 0, 0, width, height) r:setFillColor(0, 1) --and then swcaster/light.lua function \_createMask()         local m = display.newImageRect("img/lightMask.png", 256, 256) -- this image is inserted in the mask snapshot group         m.blendMode = "dstOut"         return m end  

Hope it helps.

Ivan.

#5

Thank you, Ivan!

#6

Thank you, Ivan. I have been trying for ages to figure out a way to mask a display object using another one dynamically created. Was trying all sorts of ridiculous methods of using display.save and applying the resulting files as masks. This works so much better!

#7

Thank you, Ivan. I have been trying for ages to figure out a way to mask a display object using another one dynamically created. Was trying all sorts of ridiculous methods of using display.save and applying the resulting files as masks. This works so much better!