Java FloatBuffer size error OpenGL

Question

working with LWJGL's implementation of OpenGL, and trying to work with the lighting functions. This requires the creation of FloatBuffers to pass to OpenGL. Relevant code follows:

GL11.glClearColor(0,0,0,0);

float[] ambientLight={(float).3,(float).5,(float).8,1};
FloatBuffer ambientLightB = FloatBuffer.allocate(4);
ambientLightB.put(ambientLight);

float[] diffuseLight={(float).25,(float).25,(float).25,1};
FloatBuffer diffuseLightB = FloatBuffer.allocate(4);
diffuseLightB.put(diffuseLight);

float[] lightPosition={0,0,1,1};
FloatBuffer lightPositionB = FloatBuffer.allocate(4);
lightPositionB.put(lightPosition);

float[] matAmbient={1,1,1,1};
FloatBuffer matAmbientB = FloatBuffer.allocate(4);
matAmbientB.put(matAmbient);

float[] matDiff={1,1,1,1};
FloatBuffer matDiffB = FloatBuffer.allocate(4);
matDiffB.put(matDiff);

GL11.glShadeModel(GL11.GL_SMOOTH);
GL11.glEnable(GL11.GL_DEPTH_TEST);
GL11.glEnable(GL11.GL_CULL_FACE);
GL11.glFrontFace(GL11.GL_CCW);
GL11.glEnable(GL11.GL_LIGHTING);

GL11.glMaterial(GL11.GL_FRONT,GL11.GL_AMBIENT,matAmbientB);
GL11.glMaterial(GL11.GL_FRONT, GL11.GL_DIFFUSE,matDiffB);
GL11.glLight(GL11.GL_LIGHT0,GL11.GL_AMBIENT,ambientLightB);
GL11.glLight(GL11.GL_LIGHT0,GL11.GL_DIFFUSE,diffuseLightB);
GL11.glLight(GL11.GL_LIGHT0,GL11.GL_POSITION,lightPositionB);
GL11.glEnable(GL11.GL_LIGHT0);

The first call I make to glMaterial gives the following error:

Exception in thread "main" java.lang.IllegalArgumentException: Number of remaining buffer elements is 0, must be at least 4. Because at most 4 elements can be returned, a buffer with at least 4 elements is required, regardless of actual returned element count

Not quite sure what I'm doing wrong here, seems to be a problem in the creation of the FloatBuffer.

user207421 · Accepted Answer · 2012-03-03 01:21:10Z

1

Flip() the buffer after the put(), or use FloatBuffer.wrap(), which would also save you some lines of code. Or maybe it needs another 4 slots, so allocate 8 elements.

answered Mar 3, 2012 at 1:21

user207421

312k45 gold badges324 silver badges493 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

sol_var Over a year ago

I don't see any flip() method in the java documentation of the class... Wrap doesn't work, that gives me an error saying I need a direct Buffer... Shouldn't need 8 buffers, the equivalent function call in C takes a size 4 array

sol_var Over a year ago

Flip was in the super class, gave the same direct buffer error

user207421 Over a year ago

@sol_var (1) Buffer.flip() does exist, look again. It is inherited. (2) If you really need a direct buffer, allocate() shouldn't work either, you would have to use allocateDirect(). Something wrong here. (3) There is no C equivalent of FloatBuffer. I think you're going to have to look again at the documentation for the package you're using.

sol_var Over a year ago

EJP, thank you for your information, it was very helpful. Just to clarify, by C equivalent, I meant the equivalent of the function call, not the equivalent of the FloatBuffer. In C the function glMaterialfv would be called instead for the exact same effect, and its third parameter is a pointer to a float array of size four instead of a FloatBuffer of size 4.

sol_var · Accepted Answer · 2012-03-03 14:51:06Z

1

The solution ended up requiring another function call specific to LWJGL (BufferUtils.createFloatBuffer), as well as the flip() method. The following correctly initialized the buffer

float[] matAmbient={1,1,1,1};
FloatBuffer matAmbientB = BufferUtils.createFloatBuffer(4);
matAmbientB.put(matAmbient);
matAmbientB.flip();

answered Mar 3, 2012 at 14:51

sol_var

8671 gold badge9 silver badges9 bronze badges

Comments

Istinra · Accepted Answer · 2012-03-05 10:15:55Z

The idea of using FloatBuffers with LWJGL is so native code can use there buffers directly, in order for this to work correctly they should be used like so,

//Create a directly allocated buffer in bytes (16 = 4 Floats * size of float in bytes)
ByteBuffer bytes = ByteBuffer.allocateDirect(16).order(ByteOrder.nativeOrder());
FloatBuffer fb = bytes.asFloatBuffer();
fb.put(...);
fb.rewind(); //Moves the internal buffer pointer back to the start for the next thing to read from it

The ByteOrder.nativeOrder() will ensure that whether your system uses big or little endian it will be transferred correctly from java to native code. (See http://en.wikipedia.org/wiki/Endianness)

The LWJGL buffer util likely does this for you

Collectives™ on Stack Overflow

Java FloatBuffer size error OpenGL

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related