Then added self-shadowing to the mixture and some color control just for the fun and looks of it.

In the end i thought it would be nice to take my carpet out to clean. Happy holidays!

A very early release is available http://victamin.googlecode.com/files/CLNUI4J_01.zip. This might or might not work out-of-the-box and it sure needs improvement and more work, but as they say, release early, release often. This package includes the library and basic examples running on Eclipse IDE and processing IDE (untested). It is known that this library does not work directly with Processing.

EDIT! Version 0.2 is now available at: http://victamin.googlecode.com/files/CLNUI4J_02.zip.
You can now find a friendly wrapper and a couple of examples to get you started.

I would love to get some feedback, so if you’re a Kinect owner and you’re into java/processing, give it a  spin and let me know how it works out for you.

Have fun.

Update! The link has been removed as the application was removed from online. I will get a new link ASAP.

]]> http://www.pixelnerve.com/v/2010/11/04/dt/feed/ 1 http://www.pixelnerve.com/v/2010/07/29/msaopencl-for-java-and-processing/ http://www.pixelnerve.com/v/2010/07/29/msaopencl-for-java-and-processing/#comments Thu, 29 Jul 2010 01:57:33 +0000 victormartins http://www.pixelnerve.com/v/?p=1248 Recently I have been doing some work with OpenCL and i found myself messing up with old code and re-writing most of it .  At first it was interesting and quite funny but no more, so,  I thought it was time to make things easier for myself and just make things reusable by creating a wrapper which would wrap most of the boring and time-consuming parts. This would be a wrapper on OpenCL for Java and/or Processing. Well, a well known guy named Mehmet “Memo” Akten has done such a wrapper in C++ for the OpenFrameworks and Cinder libraries. I have ported it  to Java.

There are some problems with reading/writing from/to GL textures. For some reason it crashes on me. I have been working with JavaCL‘s author, so hopefully it will be working soon.

:: Download

Download it, install it and try it.
If you find any problems or if you have suggestions, let me know.

Have fun.

So imagine we have 2 image buffers Image1, Image2. Usually to change data from Image1, you would simply access it and write directly back to the same positioion. Now, when we’re talking about a shader fragment program we can’t simply do that. You may ask now, what’s the solution? Ping-pong it!

Here is what i’m talking about:

//
// Initialization
//
int W = 100;
int H = 100;
ImageArray = new int[2][W*H];
int CurrActiveBuffer = 0; // Current active buffer index
 
 
//
// Mainloop
//
for( int j=0; j<H; j++ )
{
	for( int i=0; i<W; i++ )
	{
		// ERROR! Write to same buffer. Not possible in gpu shader
		//Image1[i+j*W] = Image1[i+j*W] * 2;  // Mul by 2
 
		// Ping-pong version
		int src = CurrActiveBuffer; // Current active buffer (Input)
		int dest = 1-CurrActiveBuffer;  // Back buffer (Output)
		ImageArray[dest][i+j*W] = ImageArray[src][i+j*W] * 2;  // Mul by 2
	}
}
 
// Swap back and front buffers (read becomes write and vice-versa)
CurrActiveBuffer = 1-CurrActiveBuffer;    // CurrActiveBuffer ? 0 : 1;

As you can see we start with buffer 0. That’s where we get out data from (read) and write it to Buffer 1. Once the operation is done, we swap buffers every frame. This way we’ll be able to use last iteration’s data as input for the next iteration.

Now let’s put this in OpenGL language. I will be using a FrameBufferObject (FBO) and 2 textures here. The framebuffer will be holding to both textures as 2 Color Attachments. So let’s get coding:

//
// Initialization
//
int W = 100;
int H = 100;
int FboID;
int TexID[2];
int CurrActiveBuffer = 0;  // Current active buffer index
 
// Create the frambuffer
glGenFramebuffersEXT( 1, &FboID );
glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, FboID );
 
// Create 2 textures for input/output.
glGenTextures( 2, TexID );
 
for( int i=0; i<2; i++ )
{
	glBindTexture( GL_TEXTURE_2D, TexID[i] );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
        // RGBA8 buffer
	glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, W, H, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL );
	if( _hasMipmapping )  glGenerateMipmapEXT( GL_TEXTURE_2D );
}
 
// Now attach textures to FBO
int src = CurrActiveBuffer;
int dest = 1-CurrActiveBuffer;
glFramebufferTexture2DEXT( GL_FRAMEBUFFER_EXT, 
                           GL_COLOR_ATTACHMENT0_EXT, 
                           GL_TEXTURE_2D, TexID[src], 0 );
glFramebufferTexture2DEXT( GL_FRAMEBUFFER_EXT, 
                           GL_COLOR_ATTACHMENT1_EXT, 
                           GL_TEXTURE_2D, TexID[dest], 0 );
);
 
 
 
//
// Mainloop
//
int src = CurrActiveBuffer;
int dest = 1-CurrActiveBuffer;
 
FBO.Bind();
 
glDrawBuffer( dest );
 
glBindTexture( GL_TEXTURE_2D, TexID[src] );
ShaderProgram.SetTextureUniform( 0 );
RenderScene();
 
FBO.Unbind();
 
 
// Swap back and front buffers (read becomes write and vice-versa)
CurrActiveBuffer = 1-CurrActiveBuffer;    // CurrActiveBuffer ? 0 : 1;

Why would you want to ping-pong? Well for instance imagine you are doing a water effect in the gpu. You’ll need to access data from your previous buffer right? Using the CPU that would be trivial as you have the last frame’s memory buffer allocated somewhere which you can read/write access directly. That doesn’t really work on the gpu side that way (but we’re getting closer with CL, CUDA, DC)

Have fun.

There is no executable this time, as i don’t know if i can spread the music, still, nobody can stop me  (for the moment) from giving you a video. So here it is, Float.

Next step was to optimize the cube generation by lowering from a 24 vertex cube to 14 vertex triangle strip. Things got better, but nothing close to my expectations. I was not satisfied, i mean, i had alot of cubes on screen (100K which was not that much) and that was it, nothing else. We’re talking about 20fps or so, for 100.000 cubes (around 1.2 million triangles per frame). Later on i added vertex normals to the geometry shader and started to work on some lighting/shadowing, but i ended up going back on the rendering side of the job. Meanwhile, i was speaking with a friend of mine about this idea and we were discussing ways to compute lighting but i couldn’t stop thinking about my real problem. So it came to me.

Previously, i have done some experiments with opengl hardware instancing, but never got  to do much about it .  What better time than now, so i grabbed the project and took it for a spin. After a few hours i had the same amount of cubes on screen with a much much better framerate. Quickly implemented some eye-candy (coloring, texturing, vertex lighting), some tweaking here and there and as i was listening to Mr. Peter Broderick (hi, i love you man) added some audio analysis to the feature list.
Last but not least, a kind of “Brownian Motion” was used to generate points in space, increased the cube count to 512*512 and watched it flow ( at 20fps ).

In conclusion, Hardware instancing was much easier to implement  and performance seems much better at first sight. Above is a video of 262.144 audio-reactive cubes with GPU animation and basic lighting at around 20fps. For my video card i think that is very good. On a sidenote, i have not given up on the geometry shaders. I am not sure what will be my next step regarding the subject (back to geometry shaders?) but for now this is it. Hardware Instancing kicked Geometry Shaders in the ass.

Download: http://victamin.googlecode.com/files/JavaCL_1_4b.zip

Have fun!

To achieve this i’ve picked Vertex Texture Fetch. It allows you to access texture data on the vertex shader. Pass a texture to the vertex shader and offset the surface vertices by the pixel’s intensity. To improve the looks, bump-mapping with multiple lights have been used. Everything presented here is generated on the GPU, even the objects. Runs nicely on a Nvidia 8200M. Lots of  space for improvement.

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