Hamid - 1 year ago 61
Android Question

# Implement page curl on android?

I was surfing the net looking for a nice effect for turning pages on Android and there just doesn't seem to be one. Since I'm learning the platform it seemed like a nice thing to be able to do is this.

I managed to find a page here: http://wdnuon.blogspot.com/2010/05/implementing-ibooks-page-curling-using.html

``````- (void)deform
{
Vertex2f  vi;   // Current input vertex
Vertex3f  v1;   // First stage of the deformation
Vertex3f *vo;   // Pointer to the finished vertex
CGFloat R, r, beta;
for (ushort ii = 0; ii < numVertices_; ii++)
{
// Get the current input vertex.
vi    = inputMesh_[ii];
// Radius of the circle circumscribed by vertex (vi.x, vi.y) around A on the x-y plane
R     = sqrt(vi.x * vi.x + pow(vi.y - A, 2));
// Now get the radius of the cone cross section intersected by our vertex in 3D space.
r     = R * sin(theta);
// Angle subtended by arc |ST| on the cone cross section.
beta  = asin(vi.x / R) / sin(theta);

// *** MAGIC!!! ***
v1.x  = r * sin(beta);
v1.y  = R + A - r * (1 - cos(beta)) * sin(theta);
v1.z  = r * (1 - cos(beta)) * cos(theta);
// Apply a basic rotation transform around the y axis to rotate the curled page.

// These two steps could be combined through simple substitution, but are left
// separate to keep the math simple for debugging and illustrative purposes.
vo    = &outputMesh_[ii];
vo->x = (v1.x * cos(rho) - v1.z * sin(rho));
vo->y =  v1.y;
vo->z = (v1.x * sin(rho) + v1.z * cos(rho));
}
}
``````

that gives an example (above) code for iPhone but I have no idea how I would go about implementing this on android. Could any of the Math gods out there please help me out with how I would go about implementing this in Android Java.

Is it possible using the native draw APIs, would I have to use openGL? Could I mimik the behaviour somehow?

Any help would be appreciated. Thanks.

****************EDIT**********************************************

I found a Bitmap Mesh example in the Android API demos: http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/graphics/BitmapMesh.html

Maybe someone could help me out on an equation to simply fold the top right corner inward diagnally across the page to create a similar effect that I can later apply shadows to to gie it more depth?