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 Drawing IZOLINES of temperature  (Read 1730 times) 0 Members and 1 Guest are viewing this topic.
poonury

Junior Newbie

 « Posted 2012-10-29 20:19:22 »

Hello everybody!

I stuck with my problem.

PROBLEM:
- very slow algorithm
- no idea how to improve it
- any existing algorithm in Java/ JOGL?

HOW I DO:
I use shader to calculate izolines of temperature and i obtain for example this:

http://imageshack.us/photo/my-images/26/izoline.png

now i must to draw in JOGL black lines on color edges. I read all pixels from GL buffer.

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21 `public BufferedImage toImage(GL gl, int w, int h)     {        gl.glReadBuffer(GL.GL_FRONT); // or GL.GL_BACK        ByteBuffer glBB = ByteBuffer.allocate(3 * w * h);         gl.glReadPixels(0, 0, w, h, GL.GL_BGR, GL.GL_BYTE, glBB);        BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);        int[] bd = ((DataBufferInt) bi.getRaster().getDataBuffer()).getData();                for (int y = 0; y < h; y++) {            for (int x = 0; x < w; x++) {                int b = 2 * glBB.get();                int g = 2 * glBB.get();                int r = 2 * glBB.get();                bd[(h - y - 1) * w + x] = (r << 16) | (g << 8) | b | 0xFF000000;            }        }        return bi;    }`

But trying find edge pixel by pixel is soooo long in time. Like this:

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20 `BufferedImage bi = toImage(m_gl, Resources.dCanvasWidth, Resources.dCanvasHeight);            for(int i=0; i< 20; ++i)            {                System.out.println( i );                for(int i1=0; i1< bi.getData().getHeight()-1; ++i1)                {                    int[] buff1;                    int[] buff2;                                        buff1 = bi.getData().getPixel(i, i1, (int[]) null );                    buff2 = bi.getData().getPixel(i, i1, (int[]) null );                                        if( !Arrays.equals(buff1, buff2) )                    {                        m_gl.glDrawPixels(i, i1,GL.GL_RGB, GL.GL_INT, blackPixel);                        m_gl.glFlush();                                           }                                    } `

Can somebody help me solve this problem?
gouessej
 « Reply #1 - Posted 2012-10-29 20:29:55 »

Hi

Maybe you can compute iso-contours in the fragment shader too.

poonury

Junior Newbie

 « Reply #2 - Posted 2012-10-29 20:39:17 »

I tried but i havent neighbour pixels.

When I calculate it without neigbours but by function calculating my color. I tried obtain izo by 10 degrees it doted or all black, or line is to width.
theagentd

« JGO Bitwise Duke »

Medals: 366
Projects: 2
Exp: 8 years

 « Reply #3 - Posted 2012-10-29 20:41:03 »

Do it in two passes and you'll have access to neighboring pixels in the second pass. You can't have each pixel depend on what's being put into neighboring pixels or you'll get a paradox. =S

Myomyomyo.
poonury

Junior Newbie

 « Reply #4 - Posted 2012-10-29 20:45:36 »

Hmm i agree with you but how i can write somthing like that?

 1  2  3  4  5  6  7  8  9 `gl.glVertexAttrib1f(vs_fTempAtribute, (float) t1.getValueInNode( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[0]));gl.glVertex2d(  Resources.mesh.getVertex( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[0] ).m_position.x,                Resources.mesh.getVertex( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[0] ).m_position.y);gl.glVertexAttrib1f(vs_fTempAtribute, (float) t1.getValueInNode( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[1]));gl.glVertex2d(  Resources.mesh.getVertex( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[1] ).m_position.x,                Resources.mesh.getVertex( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[1] ).m_position.y);gl.glVertexAttrib1f(vs_fTempAtribute, (float) t1.getValueInNode( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[2]));gl.glVertex2d(  Resources.mesh.getVertex( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[2] ).m_position.x,               Resources.mesh.getVertex( Resources.mesh.getFace( Resources.mesh.getArea(dAreaCounter).getFaceNr(dFaceCounter) ).m_dwVertex[2] ).m_position.y);`

First i put in shader a temperature and it calculate color. Where put second step? On this same vertices? I do not imagine that
theagentd

« JGO Bitwise Duke »

Medals: 366
Projects: 2
Exp: 8 years

 « Reply #5 - Posted 2012-10-29 21:23:45 »

Render what you're currently doing directly to a texture using a framebuffer object (FBO). That way you'll have the data easily accessible later. Then render (using just a single fullscreen quad) this texture to the screen (back buffer) using a different shader that finds your edges or whatever and adds them to the screen. This is called post-processing a rendered image and is pretty much what you're doing on the CPU right now, am I right?

Myomyomyo.
poonury

Junior Newbie

 « Reply #6 - Posted 2012-10-29 21:34:43 »

In the code is not as easy as in theory ;( I can't imagine how ... I need to sleep mayby tomorrow will be better.
gouessej
 « Reply #7 - Posted 2012-10-29 23:56:42 »

You can use FBObject to implement theagentd's suggestion.

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