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#ActualSimonForsman

Posted 19 October 2012 - 05:49 AM

There's a lot of discussion about splitting up the canvas into groups, and then let each thread draw the group. It gave me a whole lot of questions.

1. Wouldn't splitting up the Canvas into areas for threads to render on cause something that resembles tearing?

2. In Java, I do not know of a Java method that allows splitting bitmaps while it is being drawn. What is the logic for that? Test to see if the bitmap Rect area is over the threshold, and then stop drawing that area, while letting the other thread draw the undrawn area?

3. rip-off mentioned that I may be passing a gradually completing Canvas into methods. The possibility that this might be my bottleneck is actually quite high (as I haven't considered it before), as I have passed the same reference to the Canvas object through a lot of methods. Are there other alternatives to efficiently draw tons of bitmaps (of powers of 2, in my case) onto a Canvas?


1,2 you can access a bitmaps data array in Java (atleast on Android) and copy the parts of the array you want to the buffer you're blitting to.

3. yes, this is quite possible, unless you are blitting tons of bitmaps or using some really ineffective blitting method sending the canvas to the GPU will be the slow part. The Canvas in Java seems to be singlebuffered so you should blit to a software buffer (BufferedImage should work) and then blit that buffer to the canvas. (which means you only do a single blit to the canvas). Also, if you have layers or sections of layers that rarely change you can blit those to their own buffered images at launch + when they change and then blit those images to the main bufferedimage each frame.

#2SimonForsman

Posted 19 October 2012 - 05:34 AM

There's a lot of discussion about splitting up the canvas into groups, and then let each thread draw the group. It gave me a whole lot of questions.

1. Wouldn't splitting up the Canvas into areas for threads to render on cause something that resembles tearing?

2. In Java, I do not know of a Java method that allows splitting bitmaps while it is being drawn. What is the logic for that? Test to see if the bitmap Rect area is over the threshold, and then stop drawing that area, while letting the other thread draw the undrawn area?

3. rip-off mentioned that I may be passing a gradually completing Canvas into methods. The possibility that this might be my bottleneck is actually quite high (as I haven't considered it before), as I have passed the same reference to the Canvas object through a lot of methods. Are there other alternatives to efficiently draw tons of bitmaps (of powers of 2, in my case) onto a Canvas?


1,2 you can access a bitmaps data array in Java (atleast on Android) and copy the parts of the array you want to the buffer you're blitting to.

3. yes, this is quite possible, unless you are blitting tons of bitmaps or using some really ineffective blitting method sending the canvas to the GPU will be the slow part. The Canvas in Java seems to be singlebuffered so you should create a separate image (volatileImage should be a good choice) and blit to that and then once all the blitting is done you copy that image to the canvas.

#1SimonForsman

Posted 19 October 2012 - 05:23 AM

There's a lot of discussion about splitting up the canvas into groups, and then let each thread draw the group. It gave me a whole lot of questions.

1. Wouldn't splitting up the Canvas into areas for threads to render on cause something that resembles tearing?

2. In Java, I do not know of a Java method that allows splitting bitmaps while it is being drawn. What is the logic for that? Test to see if the bitmap Rect area is over the threshold, and then stop drawing that area, while letting the other thread draw the undrawn area?

3. rip-off mentioned that I may be passing a gradually completing Canvas into methods. The possibility that this might be my bottleneck is actually quite high (as I haven't considered it before), as I have passed the same reference to the Canvas object through a lot of methods. Are there other alternatives to efficiently draw tons of bitmaps (of powers of 2, in my case) onto a Canvas?


1,2 you can access a bitmaps data array in Java (atleast on Android) and copy the parts of the array you want to the buffer you're blitting to.

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