Java: FloatBuffer to OpenGL - wrap() vs. allocate() vs. BufferUtils.createBuffer()

Question

Datasource:

float[] v = { ... };

Working example:

FloatBuffer buf = BufferUtils.createFloatBuffer(v.length);
buf.put(v);
buf.flip(); // or buf.rewind()

The buffer can now be uploaded to opengl and works fine:

...
glBufferData(..., buf, ...);
...

Why do the following examples of the buffer creation not also work?

Not working 1:

FloatBuffer buf = FloatBuffer.wrap(v);

Not working 2:

FloatBuffer buf = FloatBuffer.allocate(v.length);
buf.put(v);
buf.flip(); // or buf.rewind()

Edit:

After browsing the API code, I found out:

In case of the working example memAddress(buf) returns a valid address, but in the other cases it returns just 0.

Additional infos:

This might also be platform dependent. I have used FloatBuffer.wrap() on Android without any problems. — Reto Koradi
– Reto Koradi, Commented Jun 23, 2015 at 3:03

Tuxxy_Thang · Accepted Answer · 2015-06-22 08:18:10Z

1

BufferUtils returns a direct buffer whereas the others might not.

You can check the directness of the wrap and allocate methods using isDirect() method. Wrappers are non direct.

answered Jun 22, 2015 at 8:18

Tuxxy_Thang

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2 Comments

You are right. Take a look to my edit in the question above.

nice, been a long time since I dabbled in there