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picking.cpp
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picking.cpp
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#include "vgl.h"
#include <cstring> // for memcpy
#include <vector>
//
// Constants
//
const unsigned int kBufferWidth = 800;
const unsigned int kBufferHeight = 600;
//
// Buffer
//
typedef unsigned short BufType;
const GLenum kBufInternalFormat = GL_RGB16;
const GLenum kBufFormat = GL_RGB;
const GLenum kBufType = GL_UNSIGNED_SHORT;
const BufType kTypeShift = sizeof(BufType) * 8 - 2;
const BufType kIDShift = 0;
#define PickColor glColor3us
//
// PickingRenderer class
//
class PickingRenderer : public vgl::Renderer
{
public:
PickingRenderer();
virtual ~PickingRenderer();
virtual void setup();
virtual void render();
bool objectAt(unsigned int x, unsigned int y, unsigned int& type, unsigned int& id);
void nextDrawingMode();
private:
void renderPickImage();
void renderVisualImage();
void drawMode(GLenum polygonMode);
void cube(const vgl::Vec3f& color);
void pickableCube(BufType itemType);
private:
GLuint _fbo; // The framebuffer object we draw the pick info to.
GLuint _pickBuffer; // The renderbuffer object for the pick data (false coloured with object IDs).
GLuint _pickDepth; // The renderbuffer object for the depth data while picking.
GLuint _pbo; // Pixel buffer for reading the pick data back into CPU memory.
unsigned int _mode; // The user-selected drawing mode.
std::vector<BufType> _pickData; // The local copy of the pick data.
};
//
// PickingViewer class
//
class PickingViewer : public vgl::Viewer
{
public:
// Extra actions
enum {
ACTION_PICK_FACE = 100, // Selected a face.
ACTION_PICK_EDGE, // Selected an edge.
ACTION_PICK_VERTEX, // Selected a vertex.
ACTION_NEXT_MODE // Switch to the next drawing mode.
};
public:
PickingViewer();
virtual ~PickingViewer();
protected:
virtual int actionForMousePress(int button, int state, int x, int y);
virtual int actionForKeyPress(unsigned int key, int x, int y);
virtual void actionHandler(int action);
protected:
unsigned int _selectedFace;
unsigned int _selectedEdge;
unsigned int _selectedVertex;
};
//
// PickingRenderer methods
//
PickingRenderer::PickingRenderer() :
_fbo(0),
_pickBuffer(0),
_pickDepth(0),
_pbo(0),
_mode(0),
_pickData()
{
}
PickingRenderer::~PickingRenderer()
{
if (_fbo)
glDeleteFramebuffers(1, &_fbo);
if (_pickBuffer)
glDeleteRenderbuffers(1, &_pickBuffer);
if (_pickDepth)
glDeleteRenderbuffers(1, &_pickDepth);
if (_pbo)
glDeleteBuffers(1, &_pbo);
}
void PickingRenderer::setup()
{
glEnable(GL_DEPTH_TEST);
GLint vp[4];
glGetIntegerv(GL_VIEWPORT, vp);
unsigned int width = vp[2];
unsigned int height = vp[3];
// Set up the pick buffer.
glGenRenderbuffers(1, &_pickBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _pickBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, kBufInternalFormat, width, height);
// Set up the depth buffer.
glGenRenderbuffers(1, &_pickDepth);
glBindRenderbuffer(GL_RENDERBUFFER, _pickDepth);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
// Set up the FBO.
glGenFramebuffers(1, &_fbo);
glBindFramebuffer(GL_FRAMEBUFFER, _fbo);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _pickBuffer);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _pickDepth);
// Set up the PBO for reading back the pick data from the FBO.
glGenBuffers(1, &_pbo);
glBindBuffer(GL_PIXEL_PACK_BUFFER, _pbo);
glBufferData(GL_PIXEL_PACK_BUFFER, sizeof(BufType) * 3 * width * height, NULL, GL_DYNAMIC_READ);
// Check that everything is OK.
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (status != GL_FRAMEBUFFER_COMPLETE) {
fprintf(stderr, "Framebuffer incomplete. Aborting.\n");
exit(-1);
}
}
void PickingRenderer::render()
{
GLint vp[4];
glGetIntegerv(GL_VIEWPORT, vp);
unsigned int width = vp[2];
unsigned int height = vp[3];
unsigned int newBufSize = width * height * 3;
if (newBufSize != _pickData.size()) {
_pickData.resize(newBufSize);
glBindRenderbuffer(GL_RENDERBUFFER, _pickBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, kBufInternalFormat, width, height);
glBindRenderbuffer(GL_RENDERBUFFER, _pickDepth);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
glBindBuffer(GL_PIXEL_PACK_BUFFER, _pbo);
glBufferData(GL_PIXEL_PACK_BUFFER, sizeof(BufType) * 3 * width * height, NULL, GL_DYNAMIC_READ);
}
// Render the selectable data
glBindFramebuffer(GL_FRAMEBUFFER, _pickBuffer);
renderPickImage();
// Start reading the selectable data back asynchronously
glBindBuffer(GL_PIXEL_PACK_BUFFER, _pbo);
glReadPixels(0, 0, width, height, kBufFormat, kBufType, (void*)0);
// Render the visual data
glBindFramebuffer(GL_FRAMEBUFFER, 0);
if (_mode == 0)
renderVisualImage();
else
renderPickImage();
// Map the selectable data so we can use it.
float* buf = (float*)glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);
if (buf) {
memcpy(_pickData.data(), buf, sizeof(BufType) * 3 * width * height);
glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
}
glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
}
bool PickingRenderer::objectAt(unsigned int x, unsigned int y, unsigned int& type, unsigned int& id)
{
GLint vp[4];
glGetIntegerv(GL_VIEWPORT, vp);
unsigned int width = vp[2];
unsigned int height = vp[3];
y = height + 1 - y;
unsigned int index = (y * width + x) * 3;
if (_pickData[index] == 0)
return false;
type = (unsigned int)_pickData[index] >> kTypeShift;
id = (unsigned int)_pickData[index + 2] >> kIDShift;
return true;
}
void PickingRenderer::nextDrawingMode()
{
_mode = 1 - _mode;
glutPostRedisplay();
}
void PickingRenderer::renderPickImage()
{
glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLineWidth(8.0);
glPointSize(10.0);
drawMode(GL_FILL);
pickableCube(1); // Draw the faces
drawMode(GL_LINE);
pickableCube(2); // Draw the lines
drawMode(GL_POINT);
pickableCube(3); // Draw the points
}
void PickingRenderer::renderVisualImage()
{
glClearColor(0.2, 0.2, 0.2, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLineWidth(1.0);
glPointSize(5.0);
drawMode(GL_FILL);
cube(vgl::Vec3f(0.3, 0.3, 0.3)); // Draw the faces
drawMode(GL_LINE);
cube(vgl::Vec3f(0.6, 0.6, 0.6)); // Draw the lines
drawMode(GL_POINT);
cube(vgl::Vec3f(0.9, 0.9, 0.9)); // Draw the points
}
void PickingRenderer::drawMode(GLenum polygonMode)
{
glPolygonMode(GL_FRONT_AND_BACK, polygonMode);
switch (polygonMode) {
case GL_LINE:
glDisable(GL_POLYGON_OFFSET_POINT);
glEnable(GL_POLYGON_OFFSET_LINE);
glPolygonOffset(-1, -3);
break;
case GL_POINT:
glPolygonOffset(-1, -5);
glEnable(GL_POLYGON_OFFSET_POINT);
glDisable(GL_POLYGON_OFFSET_LINE);
break;
case GL_FILL:
default:
glDisable(GL_POLYGON_OFFSET_POINT);
glDisable(GL_POLYGON_OFFSET_LINE);
glPolygonOffset(0, 0);
break;
}
}
void PickingRenderer::cube(const vgl::Vec3f& color)
{
vgl::Vec3f lo(-0.5, -0.5, -0.5);
vgl::Vec3f hi( 0.5, 0.5, 0.5);
glColor3fv(color.data);
glBegin(GL_QUADS);
glVertex3f(lo.x, lo.y, lo.z);
glVertex3f(hi.x, lo.y, lo.z);
glVertex3f(hi.x, hi.y, lo.z);
glVertex3f(lo.x, hi.y, lo.z);
glVertex3f(lo.x, lo.y, hi.z);
glVertex3f(hi.x, lo.y, hi.z);
glVertex3f(hi.x, hi.y, hi.z);
glVertex3f(lo.x, hi.y, hi.z);
glVertex3f(lo.x, lo.y, lo.z);
glVertex3f(lo.x, lo.y, hi.z);
glVertex3f(lo.x, hi.y, hi.z);
glVertex3f(lo.x, hi.y, lo.z);
glVertex3f(hi.x, lo.y, lo.z);
glVertex3f(hi.x, lo.y, hi.z);
glVertex3f(hi.x, hi.y, hi.z);
glVertex3f(hi.x, hi.y, lo.z);
glVertex3f(lo.x, lo.y, lo.z);
glVertex3f(hi.x, lo.y, lo.z);
glVertex3f(hi.x, lo.y, hi.z);
glVertex3f(lo.x, lo.y, hi.z);
glVertex3f(lo.x, hi.y, lo.z);
glVertex3f(hi.x, hi.y, lo.z);
glVertex3f(hi.x, hi.y, hi.z);
glVertex3f(lo.x, hi.y, hi.z);
glEnd();
}
void PickingRenderer::pickableCube(BufType itemType)
{
vgl::Vec3f lo(-0.5, -0.5, -0.5);
vgl::Vec3f hi( 0.5, 0.5, 0.5);
const float kVerts[24][3] = {
{ lo.x, lo.y, lo.z },
{ hi.x, lo.y, lo.z },
{ hi.x, hi.y, lo.z },
{ lo.x, hi.y, lo.z },
{ lo.x, lo.y, hi.z },
{ hi.x, lo.y, hi.z },
{ hi.x, hi.y, hi.z },
{ lo.x, hi.y, hi.z },
{ lo.x, lo.y, lo.z },
{ lo.x, lo.y, hi.z },
{ lo.x, hi.y, hi.z },
{ lo.x, hi.y, lo.z },
{ hi.x, lo.y, lo.z },
{ hi.x, lo.y, hi.z },
{ hi.x, hi.y, hi.z },
{ hi.x, hi.y, lo.z },
{ lo.x, lo.y, lo.z },
{ hi.x, lo.y, lo.z },
{ hi.x, lo.y, hi.z },
{ lo.x, lo.y, hi.z },
{ lo.x, hi.y, lo.z },
{ hi.x, hi.y, lo.z },
{ hi.x, hi.y, hi.z },
{ lo.x, hi.y, hi.z }
};
switch (itemType) {
case 1: // Faces
glBegin(GL_QUADS);
for (unsigned int i = 0; i < 6; ++i) {
PickColor(itemType << kTypeShift, 0, i << kIDShift);
for (int f = i * 4; f < (i + 1) * 4; ++f)
glVertex3fv(kVerts[f]);
}
glEnd();
break;
case 2: // Edges
glBegin(GL_LINES);
for (unsigned int i = 0; i < 6; ++i) {
int prev = i * 4 + 3;
for (unsigned int f = i * 4; f < (i + 1) * 4; ++f) {
PickColor(itemType << kTypeShift, 0, f << kIDShift);
glVertex3fv(kVerts[prev]);
glVertex3fv(kVerts[f]);
prev = f;
}
}
glEnd();
break;
case 3: // Verts
glBegin(GL_QUADS);
for (unsigned int i = 0; i < 24; ++i) {
PickColor(itemType << kTypeShift, 0, i << kIDShift);
glVertex3fv(kVerts[i]);
}
glEnd();
break;
default: // Regular drawing.
break;
}
}
//
// PickingViewer methods
//
PickingViewer::PickingViewer() :
vgl::Viewer("Picking Example", kBufferWidth, kBufferHeight, new PickingRenderer())
{
}
PickingViewer::~PickingViewer()
{
}
int PickingViewer::actionForMousePress(int button, int state, int x, int y)
{
if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN && !_shiftDown && !_altDown && !_ctrlDown) {
_selectedFace = 0;
_selectedEdge = 0;
_selectedVertex = 0;
PickingRenderer* picker = (PickingRenderer*)_renderer;
unsigned int type = 0;
unsigned int id = 0;
if (x >= 0 && x < _width && y >= 0 && y < _height) {
if (picker->objectAt(x, y, type, id)) {
switch (type) {
case 1: _selectedFace = id; return ACTION_PICK_FACE;
case 2: _selectedEdge = id; return ACTION_PICK_EDGE;
case 3: _selectedVertex = id; return ACTION_PICK_VERTEX;
default:
fprintf(stderr, "Unknown object type %u with id %u.\n", type, id);
break;
}
}
else {
fprintf(stderr, "Background.\n");
}
}
}
return vgl::Viewer::actionForMousePress(button, state, x, y);
}
int PickingViewer::actionForKeyPress(unsigned int key, int x, int y)
{
if (key == ' ')
return ACTION_NEXT_MODE;
return vgl::Viewer::actionForKeyPress(key, x, y);
}
void PickingViewer::actionHandler(int action)
{
switch (action) {
case ACTION_PICK_FACE: fprintf(stderr, "Picked face %u\n", _selectedFace); break;
case ACTION_PICK_EDGE: fprintf(stderr, "Picked edge %u\n", _selectedEdge); break;
case ACTION_PICK_VERTEX: fprintf(stderr, "Picked vertex %u\n", _selectedVertex); break;
case ACTION_NEXT_MODE: ((PickingRenderer*)_renderer)->nextDrawingMode(); break;
default:
vgl::Viewer::actionHandler(action);
break;
}
}
//
// Functions
//
int main(int argc, char** argv)
{
PickingViewer viewer;
viewer.run();
}