Thursday, July 31, 2008

Fun with Particles and Filters (AS3) Part 2

Yesterday I posted my first go around with some particle effects.

Today I have a new example using Blitting, which has improved performance but I am having trouble with the look and feel. I have tested it on two machines and the new version seems to get around double the frames per second and uses one-fifth the CPU usage. However, I am having trouble getting the bitmapdata to alpha out. I used a ColorMatrixFilter but that only seems to gray out the smoke... which ends up look much more polluting. You can view my progress here.

Once I figure out the alpha and clean up my code, I will post in more detail about the Blitting.


Unknown said...

so I am not sure how you are using the color matrix filter, but I have had great success applying it on an enterframe to slow fade out the bitmap.


//set up a alpha fading matrix

alphaMatrix = new ColorMatrixFilter([




0, 0, 0, 1,- 4]);

//the -4 at the end is what you want to mess with to drop the alpha

// then on an enterframe or timer or whatever, I would drop this...

yourBitmapData.applyFilter(yourBitmapData, rect, pt, alphaMatrix)

///Is that what you are doing? maybe it just has to do with orginal gradient you are using as the smoke. anyway, I look forward to your solution. Good Luck

Ickydime said...

Thanks for the comment. Sorry for the delayed response. Been meaning to get back to this.

Yes, I was using the ColorMatrix Filter, but I was using the the second to last item instead of the last item. The second to last item gets multiplied against the source's alpha and I would just decrease the percent on each update. The last item appears to be the alpha offset. So I am guessing we are doing the same thing just in a different way. But I am still fairly new to ColorMatrixFilters and need further experimenting to see what works best.

Ickydime said...

To overcome the Alpha issues I ended up adding the alphaBitmapData parameters to the copyPixels function. Basically when I applied the ColorMatrixFilter with the deceased Alpha it caused the transparent area to become grey. By Adding the Alpha information during copyPixels it seemed to remove the extra grey area, although it also seemed to decrease performance slightly.

Adriaan said...

I'm curious, is this using the movieclips you mentioned in your first post about the particles? I'm still interested in the code you used for this. What's your reason for using the ColorMatrixFilter over, say, a Tweener instance that tweens the alpha to 0?

Ickydime said...

Yeah, it is still using the basic MovieClip for reference. However, the MovieClip is never actually placed on the stage. Instead you use blitting and store the bitmapData. Using this data as a reference you copy the pixels of each particle into a single container. Since they are all in 1 container and each particle can have a different alpha... you can't use Tweener. You need to apply the alpha when you copy the pixels.

Hopefully that clears it up some.

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