How to use btTransform function getOpenGLMatrix?

[dvon]

I can't get btTransform's getOpenGLMatrix function to work. Here's what I thought should work:

var m = new Array(16);
transform.getOpenGLMatrix(m);

I've tried various other things, but can't seem to get anything back from getOpenGLMatrix. I can get my code to work if I use getBasis().getRow()... and getOrigin(), and use that to make a matrix, but that seems like a very roundabout way to do it.

(I can't setOpenGLMatrix to work either, but I assume the issue is probably the same, since both functions expect a pointer to a btScalar array in the original Bullet version.)

[kripken]

The bullet functions can't deal with a native JS object like that, I think that is the problem here. getOpenGLMatrix receives a simple float pointer. You should allocate some memory and pass it that pointer, then read from that memory. This might work but I haven't tested it:

var buffer = Ammo.malloc(16*4);
transform.getOpenGLMatrix(buffer);
var jsBuffer = HEAPF32.subarray(buffer/4, buffer/4 + 16)
Ammo.free(buffer);

[dvon]

malloc and free don't seem to be accessible. Here's something I tried. It runs, but doesn't seem to produce the correct matrix.

var buffer = Ammo.allocate(16, 'float', 1 /* ALLOC_STACK */);
var transform = new Ammo.btTransform();
transform.getOpenGLMatrix(buffer);
var matrix = Ammo.HEAPF32.subarray(buffer / 4, buffer / 4 + 16);

// Ammo.free(buffer);
Ammo.destroy(transform);

[kripken]

@cjcliffe , you were doing something similar to this, I think? Do you remember what worked for you?

[kripken]

Note that in the example above, you need to allocate 16*4 because each float takes 4 bytes.

[computersarecool]

Is there any update to this? I would like to use that function if it is possible.