OpenSubdiv/examples/simpleCpu/simpleCpuSubdivision.cpp

// CPU Subdivision with OpenSubdiv 
// -------------------------------
// In this example program, we will setup an OpenGL application that uses OSD to
// subdivide an animated mesh. It is intended to be as simple as possible and 
// not necessarily efficient. It is also intended as a learning tool for 
// understanding the OSD internals. Unlike the other OSD examples, the common 
// code infrastructure has been removed for clarity.
//
// ### Program Structure 
//
// This example program is structured as follows:
//
// 1. Setup static mesh topology (OsdHbrMesh)
// 2. Convert the topology into a subdividable mesh (OsdMesh)
// 3. On each frame: 
//      * Animate the coarse mesh points and update the OsdMesh
//      * Subdivide the updated mesh
//      * Draw the subdivided mesh and wire frame
//
// If you are completely new to OSD, you should read the following sections to 
// get a basic understanding of how it works.
//
// ### OSD Architecture Basics
// As a client, you will primarily be interacting with the Osd and Hbr classes, 
// however it's good to be aware of all three layers. The following describes
// these layers from lowest level (Hbr) to highest (Osd):
//
// **Hbr: Halfedge Boundary Representation.**
// This layer represents the mesh topology as meshes, vertices and edges. It is
// the core that provides the structure for subdivision and provides an 
// abstraction for dealing with topology in a type-agnostic way (i.e. everything
// is templated).
//
// **Far: Feature Adaptive Representation.** 
// Far uses hbr to create and cache fast run time data structures for table 
// driven subdivision. Feature-adaptive refinement logic is used to adaptively 
// refine coarse topology only as much as needed. The FarMesh does hold vertex 
// objects but the topology has been baked into FarSubdivisionTables. It also
// provides the underpinnings for generic dispatch of subdivision evaluation, so
// subdivision can be preformed with different mechanisms (GLSL, Cuda, etc.),
// the concrete implementations are specified at the next layer up.
//
// **Osd: Open Subdiv.**
// Osd contains client level code that uses Far to create concrete instances of 
// meshes and compute patch CVs with different back ends for table driven 
// subdivision. Currently, the following are supported in Osd:
//
//  * CPU / C++ with single or multiple threads 
//  * GLSL kernels with transform feedback into VBOs 
//  * OpenCL kernels 
//  * CUDA kernels
//
// The amount of hardware specific computation code is small, ~300 lines of code,
// so it isn't a large effort to support multiple different ones for different 
// clients. In the future, it is conceivable that additional dispatchers will be
// developed to target mobile devices.
//

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// ### Helper Includes

// Vector algebra and common GL machinations that have been isolated for
// clarity of the core OSD code.
//

#include "glhelpers.h"

//
// ### OpenSubdiv Includes

// The vertex and mesh headers provide abstract representations
// of verts and meshes; the
// element array buffer provides an abstract representation of an index buffer; 
// and finally, the cpu dispatcher is how subdivision work is dispatched to the
// CPU.
//

#include <far/meshFactory.h>

#include <osd/vertex.h>
#include <osd/glDrawContext.h>
#include <osd/cpuGLVertexBuffer.h>
#include <osd/cpuComputeController.h>
#include <osd/cpuComputeContext.h>

// 
// ### Global Variables & Declarations
//

// The screen width & height; current frame for animation; and the desired 
// subdivision level.
//
int g_width = 1024,
    g_height = 1024,
    g_frame = 0,
    g_level = 4;

//
// A center point for the view matrix and the object size for framing
//
float g_center[3] = {0.0f, 0.0f, 0.0f},
      g_size = 0.0f;

//
// The OSD state: a mesh, vertex buffer and element array
//
OpenSubdiv::FarMesh<OpenSubdiv::OsdVertex> * g_farmesh = 0;
OpenSubdiv::OsdCpuGLVertexBuffer * g_vertexBuffer = 0;
OpenSubdiv::OsdGLDrawContext * g_drawContext = 0;
OpenSubdiv::OsdCpuComputeContext * g_osdComputeContext = 0;
OpenSubdiv::OsdCpuComputeController * g_osdComputeController = 0;

typedef OpenSubdiv::HbrMesh<OpenSubdiv::OsdVertex>     OsdHbrMesh;
typedef OpenSubdiv::HbrVertex<OpenSubdiv::OsdVertex>   OsdHbrVertex;
typedef OpenSubdiv::HbrFace<OpenSubdiv::OsdVertex>     OsdHbrFace;
typedef OpenSubdiv::HbrHalfedge<OpenSubdiv::OsdVertex> OsdHbrHalfedge;

//
// The coarse mesh positions and normals are saved externally and deformed
// during playback.
//
std::vector<float> g_orgPositions,
                   g_normals;

// 
// Forward declarations. These functions will be described below as they are 
// defined.
//
void idle();
void reshape(int width, int height);
void createOsdContext(int level);
void display();
void updateGeom();
static void calcNormals(OsdHbrMesh * mesh, 
                        std::vector<float> const & pos, 
                        std::vector<float> & result );

//
// ### The main program entry point
//

// register the Osd CPU kernel, 
// call createOsdMesh (see below), init glew and one-time GL state and enter the
// main drawing loop.
//
void initOsd() 
{
    initGL();
    // 
    // Dispatchers are created from a kernel enumeration via the factory pattern,
    // calling register here ensures that the CPU dispatcher will be available
    // for construction when it is requested via the kCPU enumeration inside the
    // function createOsdMesh.
    //
//    OpenSubdiv::OsdCpuKernelDispatcher::Register();
    g_osdComputeController = new OpenSubdiv::OsdCpuComputeController();

    //
    // The following method will populate the g_osdMesh object, which will 
    // contain the precomputed subdivision tables.
    //
    createOsdContext(g_level);

}

//
// ### Construct the OSD Mesh 

// Here is where the real meat of the OSD setup happens. The mesh topology is 
// created and stored for later use. Actual subdivision happens in updateGeom 
// which gets called at the end of this function and on frame change.
//
void
createOsdContext(int level)
{
    // 
    // Setup an OsdHbr mesh based on the desired subdivision scheme
    //
    static OpenSubdiv::HbrCatmarkSubdivision<OpenSubdiv::OsdVertex>  _catmark;
    OsdHbrMesh *hmesh(new OsdHbrMesh(&_catmark));

    //
    // Now that we have a mesh, we need to add verticies and define the topology.
    // Here, we've declared the raw vertex data in-line, for simplicity
    //
    float verts[] = {    0.000000f, -1.414214f, 1.000000f,
                        1.414214f, 0.000000f, 1.000000f,
                        -1.414214f, 0.000000f, 1.000000f,
                        0.000000f, 1.414214f, 1.000000f,
                        -1.414214f, 0.000000f, -1.000000f,
                        0.000000f, 1.414214f, -1.000000f,
                        0.000000f, -1.414214f, -1.000000f,
                        1.414214f, 0.000000f, -1.000000f
                        };

    //
    // The cube faces are also in-lined, here they are specified as quads
    //
    int faces[] = {
                        0,1,3,2,
                        2,3,5,4,
                        4,5,7,6,
                        6,7,1,0,
                        1,7,5,3,
                        6,0,2,4
                        };
    //
    // Record the original vertex positions and add verts to the mesh.
    //
    // OsdVertex is really just a place holder, it doesn't care what the 
    // position of the vertex is, it's just being used here as a means of
    // defining the mesh topology.
    //
    for (unsigned i = 0; i < sizeof(verts)/sizeof(float); i += 3) {
        g_orgPositions.push_back(verts[i+0]);
        g_orgPositions.push_back(verts[i+1]);
        g_orgPositions.push_back(verts[i+2]);
        
        OpenSubdiv::OsdVertex vert;
        hmesh->NewVertex(i/3, vert);
    }

    //
    // Now specify the actual mesh topology by processing the faces array 
    //
    const unsigned VERTS_PER_FACE = 4;
    for (unsigned i = 0; i < sizeof(faces)/sizeof(int); i += VERTS_PER_FACE) {
        //
        // Do some sanity checking. It is a good idea to keep this in your 
        // code for your personal sanity as well.
        //
        // Note that this loop is not changing the HbrMesh, it's purely validating
        // the topology that is about to be created below.
        //
        for (unsigned j = 0; j < VERTS_PER_FACE; j++) {
            OsdHbrVertex * origin      = hmesh->GetVertex(faces[i+j]);
            OsdHbrVertex * destination = hmesh->GetVertex(faces[i+((j+1)%VERTS_PER_FACE)]);
            OsdHbrHalfedge * opposite  = destination->GetEdge(origin);

            if(origin==NULL || destination==NULL) {
                std::cerr << 
                    " An edge was specified that connected a nonexistent vertex"
                    << std::endl;
                exit(1);
            }

            if(origin == destination) {
                std::cerr << 
                    " An edge was specified that connected a vertex to itself" 
                    << std::endl;
                exit(1);
            }

            if(opposite && opposite->GetOpposite() ) {
                std::cerr << 
                    " A non-manifold edge incident to more than 2 faces was found" 
                    << std::endl;
                exit(1);
            }

            if(origin->GetEdge(destination)) {
                std::cerr << 
                    " An edge connecting two vertices was specified more than once."
                    " It's likely that an incident face was flipped" 
                    << std::endl;
                exit(1);
            }
        }
        // 
        // Now, create current face given the number of verts per face and the 
        // face index data.
        //
        /* OsdHbrFace * face = */ hmesh->NewFace(VERTS_PER_FACE, faces+i, 0);

        //
        // If you had ptex data, you would set it here, for example
        //
        /* face->SetPtexIndex(ptexIndex) */

    }

    //
    // Apply some tags to drive the subdivision algorithm. Here we set the 
    // default boundary interpolation mode along with a corner sharpness. See 
    // the API and the renderman spec for the full list of available operations.
    //
    hmesh->SetInterpolateBoundaryMethod( OsdHbrMesh::k_InterpolateBoundaryEdgeOnly );
    
    OsdHbrVertex * v = hmesh->GetVertex(0);
    v->SetSharpness(2.7f);

    //
    // Finalize the mesh object. The Finish() call is a signal to the internals 
    // that optimizations can be made on the mesh data. 
    //
    hmesh->Finish();

    //
    // Setup some raw vectors of data. Remember that the actual point values were
    // not stored in the OsdVertex, so we keep track of them here instead
    //
    g_normals.resize(g_orgPositions.size(),0.0f);
    calcNormals( hmesh, g_orgPositions, g_normals );

    // 
    // At this point, we no longer need the topological structure of the mesh, 
    // so we bake it down into subdivision tables by converting the HBR mesh 
    // into an OSD mesh. Note that this is just storing the initial subdivision
    // tables, which will be used later during the actual subdivision process.
    //
    // Again, no vertex positions are being stored here, the point data will be 
    // sent to the mesh in updateGeom().
    //
    OpenSubdiv::FarMeshFactory<OpenSubdiv::OsdVertex> meshFactory(hmesh, level);

    g_farmesh = meshFactory.Create();

    g_osdComputeContext = OpenSubdiv::OsdCpuComputeContext::Create(g_farmesh);

    delete hmesh;

    // 
    // Initialize draw context and vertex buffer
    //
    g_vertexBuffer = 
        OpenSubdiv::OsdCpuGLVertexBuffer::Create(6,  /* 3 floats for position, 
                                                            +
                                                            3 floats for normal*/
                                                 g_farmesh->GetNumVertices());

    g_drawContext =
        OpenSubdiv::OsdGLDrawContext::Create(g_farmesh->GetPatchTables(), false);
    g_drawContext->UpdateVertexTexture(g_vertexBuffer);

    // 
    // Setup camera positioning based on object bounds. This really has nothing
    // to do with OSD.
    //
    computeCenterAndSize(g_orgPositions, g_center, &g_size);

    //
    // Finally, make an explicit call to updateGeom() to force creation of the 
    // initial buffer objects for the first draw call.
    //
    updateGeom();

    //
    // The OsdVertexBuffer provides GL identifiers which can be bound in the 
    // standard way. Here we setup a single VAO and enable points and normals 
    // as attributes on the vertex buffer and set the index buffer.
    //
    GLuint vao;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);
    glBindBuffer(GL_ARRAY_BUFFER, g_vertexBuffer->BindVBO());
    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof (GLfloat) * 6, 0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof (GLfloat) * 6, (float*)12);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_drawContext->patchIndexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

//
// ### Update Geometry and Subdivide

// This is where the magic happens. Given the initial subdivision table stored 
// in the OsdMesh, on every frame we can now send coarse point position updates 
// and recompute the subdivided surface based on the coarse animation.
//
void
updateGeom() 
{
    int nverts = (int)g_orgPositions.size() / 3;

    std::vector<float> vertex;
    vertex.reserve(nverts*6);

    const float *p = &g_orgPositions[0];
    const float *n = &g_normals[0];

    //
    // Apply a simple deformer to the coarse mesh. We save the deformed points 
    // and normals into a separate buffer to avoid accumulation of error. This 
    // loop really has nothing to do with OSD.
    // 
    float r = sin(g_frame*0.001f);
    for (int i = 0; i < nverts; ++i) {
        //float move = 0.05f*cosf(p[0]*20+g_frame*0.01f);
        float ct = cos(p[2] * r);
        float st = sin(p[2] * r);
        
        vertex.push_back(p[0]*ct + p[1]*st);
        vertex.push_back(-p[0]*st + p[1]*ct);
        vertex.push_back(p[2]);

        //
        // To be completely accurate, we should deform the normals here too, but
        // the original undeformed normals are sufficient for this example 
        //
        vertex.push_back(n[0]);
        vertex.push_back(n[1]);
        vertex.push_back(n[2]);
 
        p += 3;
        n += 3;
    }

    //
    // Send the animated coarse positions and normals to the vertex buffer.
    //
    //std::cout << vertex.size() << " - " << nverts << std::endl;
    g_vertexBuffer->UpdateData(&vertex[0], 0, nverts);

    //
    // Dispatch subdivision work based on the coarse vertex buffer. At this 
    // point, the assigned dispatcher will queue up work, potentially in many
    // worker threads. If the subdivided data is required for further processing
    // a call to Synchronize() will allow you to block until the worker threads
    // complete.
    //
    g_osdComputeController->Refine(g_osdComputeContext,
                                   g_farmesh->GetKernelBatches(),
                                   g_vertexBuffer);

    //
    // The call to Synchronize() is not actually necessary, it's being used
    // here only for illustration. 
    //
    // g_osdComputeController->Synchronize();
}

//
// ### Calculate Face Normals

// A helper function to calculate face normals. It is included here to illustrate
// how to inspect the coarse mesh, give an HbrMesh pointer.
//
static void
calcNormals(OsdHbrMesh * mesh, 
            std::vector<float> const & pos,
            std::vector<float> & result ) 
{
    //
    // Get the number of vertices and faces. Notice the naming convention is 
    // different between coarse Vertices and Faces. This may change in the 
    // future (it an artifact of the original renderman code).
    //
    int nverts = mesh->GetNumVertices();
    int nfaces = mesh->GetNumCoarseFaces();

    for (int i = 0; i < nfaces; ++i) {

        OsdHbrFace * f = mesh->GetFace(i);

        float const * p0 = &pos[f->GetVertex(0)->GetID()*3],
                    * p1 = &pos[f->GetVertex(1)->GetID()*3],
                    * p2 = &pos[f->GetVertex(2)->GetID()*3];

        float n[3];
        cross( n, p0, p1, p2 );

        for (int j = 0; j < f->GetNumVertices(); j++) {
            int idx = f->GetVertex(j)->GetID() * 3;
            result[idx  ] += n[0];
            result[idx+1] += n[1];
            result[idx+2] += n[2];
        }
    }
    for (int i = 0; i < nverts; ++i)
        normalize(&result[i*3]);
}


//
// ### Draw the Mesh 

// Display handles all drawing per frame. We first call the setupForDisplay 
// helper method to setup some uninteresting GL state and then bind the mesh
// using the buffers provided by our OSD objects
//
void
display() 
{
    setupForDisplay(g_width, g_height, g_size, g_center);

    //
    // Bind the GL vertex and index buffers
    //
    glBindBuffer(GL_ARRAY_BUFFER, g_vertexBuffer->BindVBO());

    OpenSubdiv::OsdDrawContext::PatchArrayVector const & patches = g_drawContext->patchArrays;
    for (int i=0; i<(int)patches.size(); ++i) {
        OpenSubdiv::OsdDrawContext::PatchArray const & patch = patches[i];

        //
        // Bind the solid shaded program and draw elements based on the buffer contents
        //
        bindProgram(g_quadFillProgram);

        glDrawElements(GL_LINES_ADJACENCY, patch.GetNumIndices(),
                       GL_UNSIGNED_INT, NULL);

        //
        // Draw the wire frame over the solid shaded mesh
        //
        bindProgram(g_quadLineProgram);
        glUniform4f(glGetUniformLocation(g_quadLineProgram, "fragColor"), 
                    0, 0, 0.5, 1);
        glDrawElements(GL_LINES_ADJACENCY, patch.GetNumIndices(),
                       GL_UNSIGNED_INT, NULL);
    }

    //
    // This isn't strictly necessary, but unbind the GL state
    //
    glUseProgram(0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    //glDisableClientState(GL_VERTEX_ARRAY);

    //
    // Draw the HUD/status text
    //
    //glColor3f(1, 1, 1);
    drawString(10, 10, "LEVEL = %d", g_level);
    drawString(10, 30, "# of Vertices = %d", g_farmesh->GetNumVertices());
    drawString(10, 50, "KERNEL = CPU");
    drawString(10, 70, "SUBDIVISION = %s", "CATMARK");

    //
    // Finish the current frame
    //
    glFinish();
}