/**
* Updates the plane model transform matrix and extents.
*/
private void updatePlaneParameters(float[] planeMatrix, float extentX, float extentZ,
FloatBuffer boundary)
{
Array.Copy(planeMatrix, 0, mModelMatrix, 0, 16);
if (boundary == null)
{
mVertexBuffer.Limit(0);
mIndexBuffer.Limit(0);
return;
}
// Generate a new set of vertices and a corresponding triangle strip index set so that
// the plane boundary polygon has a fading edge. This is done by making a copy of the
// boundary polygon vertices and scaling it down around center to push it inwards. Then
// the index buffer is setup accordingly.
boundary.Rewind();
int boundaryVertices = boundary.Limit() / 2;
int numVertices;
int numIndices;
numVertices = boundaryVertices * VERTS_PER_BOUNDARY_VERT;
// drawn as GL_TRIANGLE_STRIP with 3n-2 triangles (n-2 for fill, 2n for perimeter).
numIndices = boundaryVertices * INDICES_PER_BOUNDARY_VERT;
if (mVertexBuffer.Capacity() < numVertices * COORDS_PER_VERTEX)
{
int size = mVertexBuffer.Capacity();
while (size < numVertices * COORDS_PER_VERTEX)
{
size *= 2;
}
mVertexBuffer = ByteBuffer.AllocateDirect(BYTES_PER_FLOAT * size)
.Order(ByteOrder.NativeOrder()).AsFloatBuffer();
}
mVertexBuffer.Rewind();
mVertexBuffer.Limit(numVertices * COORDS_PER_VERTEX);
if (mIndexBuffer.Capacity() < numIndices)
{
int size = mIndexBuffer.Capacity();
while (size < numIndices)
{
size *= 2;
}
mIndexBuffer = ByteBuffer.AllocateDirect(BYTES_PER_SHORT * size)
.Order(ByteOrder.NativeOrder()).AsShortBuffer();
}
mIndexBuffer.Rewind();
mIndexBuffer.Limit(numIndices);
// Note: when either dimension of the bounding box is smaller than 2*FADE_RADIUS_M we
// generate a bunch of 0-area triangles. These don't get rendered though so it works
// out ok.
float xScale = Math.Max((extentX - 2 * FADE_RADIUS_M) / extentX, 0.0f);
float zScale = Math.Max((extentZ - 2 * FADE_RADIUS_M) / extentZ, 0.0f);
while (boundary.HasRemaining)
{
float x = boundary.Get();
float z = boundary.Get();
mVertexBuffer.Put(x);
mVertexBuffer.Put(z);
mVertexBuffer.Put(0.0f);
mVertexBuffer.Put(x * xScale);
mVertexBuffer.Put(z * zScale);
mVertexBuffer.Put(1.0f);
}
// step 1, perimeter
mIndexBuffer.Put((short)((boundaryVertices - 1) * 2));
for (int i = 0; i < boundaryVertices; ++i)
{
mIndexBuffer.Put((short)(i * 2));
mIndexBuffer.Put((short)(i * 2 + 1));
}
mIndexBuffer.Put((short)1);
// This leaves us on the interior edge of the perimeter between the inset vertices
// for boundary verts n-1 and 0.
// step 2, interior:
for (int i = 1; i < boundaryVertices / 2; ++i)
{
mIndexBuffer.Put((short)((boundaryVertices - 1 - i) * 2 + 1));
mIndexBuffer.Put((short)(i * 2 + 1));
}
if (boundaryVertices % 2 != 0)
{
mIndexBuffer.Put((short)((boundaryVertices / 2) * 2 + 1));
}
}