Function tesselate_sphere

compute/example/opengl_sphere.cpp:41–112

tesselates a sphere with radius, phi_slices, and theta_slices. returns a shared opencl/opengl buffer containing the vertex data.

// tesselates a sphere with radius, phi_slices, and theta_slices. returns
// a shared opencl/opengl buffer containing the vertex data.
compute::opengl_buffer tesselate_sphere(float radius,
                                        size_t phi_slices,
                                        size_t theta_slices,
                                        compute::command_queue &queue)
{
    using compute::dim;

    const compute::context &context = queue.get_context();

    const size_t vertex_count = phi_slices * theta_slices;

    // create opengl buffer
    GLuint vbo;
    vtkgl::GenBuffersARB(1, &vbo);
    vtkgl::BindBufferARB(vtkgl::ARRAY_BUFFER, vbo);
    vtkgl::BufferDataARB(vtkgl::ARRAY_BUFFER,
                         sizeof(float) * 4 * vertex_count,
                         NULL,
                         vtkgl::STREAM_DRAW);
    vtkgl::BindBufferARB(vtkgl::ARRAY_BUFFER, 0);

    // create shared opengl/opencl buffer
    compute::opengl_buffer vertex_buffer(context, vbo);

    // tesselate_sphere kernel source
    const char source[] = BOOST_COMPUTE_STRINGIZE_SOURCE(
        __kernel void tesselate_sphere(float radius,
                                       uint phi_slices,
                                       uint theta_slices,
                                       __global float4 *vertex_buffer)
        {
            const uint phi_i = get_global_id(0);
            const uint theta_i = get_global_id(1);

            const float phi = phi_i * 2.f * M_PI_F / phi_slices;
            const float theta = theta_i * 2.f * M_PI_F / theta_slices;

            float4 v;
            v.x = radius * cos(theta) * cos(phi);
            v.y = radius * cos(theta) * sin(phi);
            v.z = radius * sin(theta);
            v.w = 1.f;

            vertex_buffer[phi_i*phi_slices+theta_i] = v;
        }
    );

    // build tesselate_sphere program
    compute::program program =
        compute::program::create_with_source(source, context);
    program.build();

    // setup tesselate_sphere kernel
    compute::kernel kernel(program, "tesselate_sphere");
    kernel.set_arg<compute::float_>(0, radius);
    kernel.set_arg<compute::uint_>(1, phi_slices);
    kernel.set_arg<compute::uint_>(2, theta_slices);
    kernel.set_arg(3, vertex_buffer);