[simonhayles]

Hi there,
I'm developing a program on the Nokia 6230i using jsr184.
I can display an m3g model ok, but I'm having trouble converting 3D coordinates to screen coordinates. Is there any way of giving jsr184 a set of coordinates (x,y,z) for a given camera position & projection and getting 2D (x,y) coordinates for the screen?

[mikbry]

Hi,

I have use a 3D to 2D transformation for my wireframe M3G demo.
You need to understand OpenGL transformation pipeline, it works the same.

Here you get a VertexArray from a Mesh, and at the end you fill a float array vertices2D filled with Transformed 2D points.

BR,

Mik
www.miklabs.com

Here is the code:
float mwidth = canvas.getWidth()/2;
float mheight = canvas.getHeight()/2;
VertexArray va = mesh.getVertexBuffer().getPositions(params);

// ModelView transformation
meshTransform.transform(va, qvertices, true);
float r = params[0];
// SCale vertices
for (int i = 0; i < vertexCount; i++)
{
qvertices[i*4+0] *= r;
qvertices[i*4+1] *= r;
qvertices[i*4+2] *= r;
qvertices[i*4+3] = 1.0f; // Not so usefull...
}
cameraTransform.transform(qvertices);

// Projection transformation
Transform t = new Transform();
camera.getProjection(t);
t.transform(qvertices);

// ClipCoordinates to Windows coordinates loop
for (int i = 0; i < vertexCount; i++)
{
float w = 1.0f/qvertices[i*4+3];
// Perspective division
float x = qvertices[i*4+0]*w;
float y = qvertices[i*4+1]*w;
// We now get Normalized device coordinates

// ViewPort transformation
vertices2d[i*2+0] = (int)(x*mwidth+mwidth);
vertices2d[i*2+1] = (int)(-y*mheight+mheight);
}