Processing 1.0 - Processing Discourse - choosing the PGraphics we'd like to draw on

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choosing the PGraphics we'd like to draw on (Read 5708 times)

antiplastik

choosing the PGraphics we'd like to draw on
Jun 30^th, 2008, 1:24am

PhiLho wrote on Jun 29^th, 2008, 2:56pm:

It would be nice to have an instruction telling Processing that any further graphic command will go in a given buffer, but I don't know if such command exists yet.

So we could do something like this :
Code:

PGraphics buffer = createGraphics(width, height, P3D);
buffer.beginDraw();

nextDrawingInstructionsWillDrawOn(buffer);
 fill(200);
 rect(10, 10, width-20, height-20);

nextDrawingInstructionsWillDrawOnMainScreen();
 fill(250, 150, 0);
 rect(10, 10, width-20, height-20);

buffer.endDraw();

instead of specifying the buffer everytime there's a drawing instruction :

Code:

buffer.background(255);
buffer.fill(200);
buffer.stroke(250, 150, 0);
buffer.rect(10, 10, width-20, height-20);
buffer...

which gets really annoying when there's more than 20 instructions...

What do you think? Any pros/cons that comes to your mind?

davbol

Re: choosing the PGraphics we'd like to draw on
Reply #1 - Jun 30^th, 2008, 4:49pm

your "buffer." syntax is the "right" way to do it.

but, since the papplet calls just redirect to the pgraphics (and potentially the recorder)...

this is probably considered a "hack" approach, so not officially sanctioned, but you can often get away with swapping in/out the "g" reference like so:

Quote:

PGraphics originalG;
PGraphics bufferG;

void setup() {
size(400,400,JAVA2D);
originalG = g;
bufferG = createGraphics(200,200,JAVA2D);
}

void useBufferG() {
g.endDraw();
g = bufferG;
g.beginDraw();
}

void useOriginalG() {
g.endDraw();
g = originalG;
g.beginDraw();
}

void draw() {
// main screen red background, green line
useOriginalG();
background(255,0,0);
stroke(0,255,0);
strokeWeight(3);
line(10,10,390,390);
// offscreen blue background, yellow line
useBufferG();
background(0,0,255);
stroke(255,255,0);
strokeWeight(3);
line(10,10,190,190);
// blit the offscreen to center of main screen
useOriginalG();
image(bufferG,100,100);
}

(you might also be able to just use the recorder mechanism -- if you don't mind that drawing also occurs on the main graphics)

antiplastik God Member Offline Posts: 699 France	Re: choosing the PGraphics we'd like to draw on Reply #2 - Jun 30^th, 2008, 5:57pm wow, that trick is very helpful. thank you very much for this explanation. ps: you should add it to the hacks section ;-)

mhuyck YaBB Newbies Offline Posts: 45 MA	Re: choosing the PGraphics we'd like to draw on Reply #3 - Jun 30^th, 2008, 6:06pm Clever! I like it.

Cedric

Re: choosing the PGraphics we'd like to draw on
Reply #4 - Jun 30^th, 2008, 7:55pm

I guess i have to admit that i dont get what is going on there...Maybe im a bit confused by 2 different images and showing the one above the other.
How would it look like if I want to choose between saving an image to a file or show it onscreen?

--------edit:

Seems that the unlekkers Tilesaver is more what ive been looking for, but i still encounter some problems. Ive somebody used it before and knows whats wrong i appreciate help

http://processing.org/discourse/yabb_beta/YaBB.cgi?board=LibraryProblems;action=display;num=1214850610;start=0

twitter.com/CedricKiefer

Al_11

Re: choosing the PGraphics we'd like to draw on
Reply #5 - Dec 26^th, 2009, 3:10pm

// blit the offscreen to center of main screen
useOriginalG();
image(bufferG,100,100);
...
In P3D mode it works very well, but when I use "bufferG = createGraphics(1180,700,OPENGL);" It gives NullPointerException for the string "image(bufferG,1180,800);". Do you how to use it with OPENGL? Where can I read about that?

antiplastik God Member Offline Posts: 699 France	Re: choosing the PGraphics we'd like to draw on Reply #6 - Dec 26^th, 2009, 3:54pm Here is what the reference says : Quote: It's not possible to use createGraphics() with OPENGL, because it doesn't allow offscreen use.

Al_11 Junior Member Offline Posts: 75	Re: choosing the PGraphics we'd like to draw on Reply #7 - Dec 26^th, 2009, 4:03pm Do I need to use OPENGL offscreen buffer in this case?

PhiLho

Re: choosing the PGraphics we'd like to draw on
Reply #8 - Dec 27^th, 2009, 3:34am

Your question makes no sense, the quoted reference seems quite clear: "OPENGL [...] doesn't allow offscreen use"
OpenGL is managed by the GPU, the graphics card, acting on the video buffer, ie. directly on-screen. It cannot act off-screen. Either you draw something more or less flat in another mode and use that as an OpenGL texture, or use P3D if you need 3D off-screen, as it creates 3D with CPU, so anywhere you want.

frankBerg YaBB Newbies Offline Posts: 27	Re: choosing the PGraphics we'd like to draw on Reply #9 - Dec 27^th, 2009, 4:22am for off-screen rendering with OpenGL have a look at the glgraphics library

Al_11 Junior Member Offline Posts: 75	Re: choosing the PGraphics we'd like to draw on Reply #10 - Dec 27^th, 2009, 8:52am Thank you all for the explanation - I understood where to start from.

PhiLho

Re: choosing the PGraphics we'd like to draw on
Reply #11 - Dec 28^th, 2009, 4:43am

For reference, after frankBerg's message, I searched opengl offscreen rendering with Google and found some hints...
Some advices are to make a hidden window: so OpenGL do the usual rendering in video buffer but it doesn't show on screen.
I also saw a reference to pBuffers (pixel buffers), faking a window memory, if I understood correctly.
So, there are tricks for off-screen OpenGL rendering. They just don't come out of the box in Processing!

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