void divide_patch( vec4 p[4][4], int count )
{
if ( count > 0 ) {
vec4 q[4][4], r[4][4], s[4][4], t[4][4];
vec4 a[4][4], b[4][4];
// subdivide curves in u direction, transpose results, divide
// in u direction again (equivalent to subdivision in v)
for ( int k = 0; k < 4; ++k ) {
divide_curve( p[k], a[k], b[k] );
}
transpose( a );
transpose( b );
for ( int k = 0; k < 4; ++k ) {
divide_curve( a[k], q[k], r[k] );
divide_curve( b[k], s[k], t[k] );
}
// recursive division of 4 resulting patches
divide_patch( q, count - 1 );
divide_patch( r, count - 1 );
divide_patch( s, count - 1 );
divide_patch( t, count - 1 );
}
else {
draw_patch( p );
}
}
GLuint LoadTeapotVAO(int &outNumVertices, GLuint positionAttribute, int NumTimesToSubdivide, int PatchesPerSubdivision){
int NumQuadsPerPatch =
(int) std::ceil(std::pow((float) PatchesPerSubdivision, (float)NumTimesToSubdivide ));
int NumTriangles =
( NumTeapotPatches * NumQuadsPerPatch * 4 /* triangles / quad */ );
int NumVertices =
( NumTriangles * 3 /* vertices / triangle */ );
outNumVertices = NumVertices;
cout << "Num of Vertices in teapot "<<NumVertices<<" Number of patches "<<NumTeapotPatches<<endl;
points = new vec4[NumVertices];
for (int zOffset = -1;zOffset<=1;zOffset +=2){
for ( int n = 0; n < NumTeapotPatches; n++ ) {
vec4 patch[4][4];
// Initialize each patch's control point data
for ( int i = 0; i < 4; ++i ) {
for ( int j = 0; j < 4; ++j ) {
vec3& v = vertices[indices[n][i][j]];
patch[i][j] = vec4( v[X], v[Y], v[Z]*zOffset, 1.0 );
}
}
// Subdivide the patch
divide_patch( patch, NumTimesToSubdivide );
}
}
// Create a vertex array object
GLuint vao;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
// Create and initialize a buffer object
GLuint buffer;
glGenBuffers( 1, &buffer );
glBindBuffer( GL_ARRAY_BUFFER, buffer );
glBufferData( GL_ARRAY_BUFFER, sizeof(vec4)*NumVertices, points, GL_STATIC_DRAW );
// set up vertex arrays
glEnableVertexAttribArray( positionAttribute );
glVertexAttribPointer( positionAttribute, 4, GL_FLOAT, GL_FALSE, 0, (const GLvoid *)0);
delete [] points;
outNumVertices = NumVertices;
return vao;
}
void
init( void )
{
for ( int n = 0; n < NumTeapotPatches; n++ ) {
point4 patch[4][4];
// Initialize each patch's control point data
for ( int i = 0; i < 4; ++i ) {
for ( int j = 0; j < 4; ++j ) {
point3& v = vertices[indices[n][i][j]];
patch[i][j] = point4( v[X], v[Y], v[Z], 1.0 );
}
}
// Subdivide the patch
divide_patch( patch, NumTimesToSubdivide );
}
// Create a vertex array object
GLuint vao;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
// Create and initialize a buffer object
GLuint buffer;
glGenBuffers( 1, &buffer );
glBindBuffer( GL_ARRAY_BUFFER, buffer );
glBufferData( GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW );
// Load shaders and use the resulting shader program
GLuint program = InitShader( "vshader_a10.glsl", "fshader_a10.glsl" );
glUseProgram( program );
// set up vertex arrays
GLuint vPosition = glGetAttribLocation( program, "vPosition" );
glEnableVertexAttribArray( vPosition );
glVertexAttribPointer( vPosition, 4, GL_FLOAT, GL_FALSE, 0,
BUFFER_OFFSET(0) );
Projection = glGetUniformLocation( program, "Projection" );
glPolygonMode( GL_FRONT_AND_BACK, GL_LINE );
glClearColor( 1.0, 1.0, 1.0, 1.0 );
}
