misc05_picking_slow_easy.cpp

// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <sstream>

// Include GLEW
#include <GL/glew.h>

// Include GLFW
#include <GLFW/glfw3.h>
GLFWwindow* window;

// Include GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/quaternion.hpp>
#include <glm/gtx/quaternion.hpp>
using namespace glm;

// Include AntTweakBar
#include <AntTweakBar.h>

#include <common/shader.hpp>
#include <common/texture.hpp>
#include <common/controls.hpp>
#include <common/objloader.hpp>
#include <common/vboindexer.hpp>

int main( void )
{
	// Initialize GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW\n" );
		getchar();
		return -1;
	}

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make macOS happy; should not be needed
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Misc 05 - Simple but slow version", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n" );
		getchar();
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	// Initialize GLEW
	glewExperimental = true; // Needed for core profile
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW\n");
		getchar();
		glfwTerminate();
		return -1;
	}

	// Initialize the GUI
	TwInit(TW_OPENGL_CORE, NULL);
	TwWindowSize(1024, 768);
	TwBar * GUI = TwNewBar("Picking");
	TwSetParam(GUI, NULL, "refresh", TW_PARAM_CSTRING, 1, "0.1");
	std::string message;
	TwAddVarRW(GUI, "Last picked object", TW_TYPE_STDSTRING, &message, NULL);

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
	glfwSetCursorPos(window, 1024/2, 768/2);

	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

	// Enable depth test
	glEnable(GL_DEPTH_TEST);
	// Accept fragment if it is closer to the camera than the former one
	glDepthFunc(GL_LESS); 

	// Cull triangles which normal is not towards the camera
	glEnable(GL_CULL_FACE);

	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);

	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "StandardShading.vertexshader", "StandardShading.fragmentshader" );
	GLuint pickingProgramID = LoadShaders( "Picking.vertexshader", "Picking.fragmentshader" );



	// Get a handle for our "MVP" uniform
	GLuint MatrixID = glGetUniformLocation(programID, "MVP");
	GLuint ViewMatrixID = glGetUniformLocation(programID, "V");
	GLuint ModelMatrixID = glGetUniformLocation(programID, "M");
	GLuint PickingMatrixID = glGetUniformLocation(pickingProgramID, "MVP");

	// Load the texture
	GLuint Texture = loadDDS("uvmap.DDS");
	
	// Get a handle for our "myTextureSampler" uniform
	GLuint TextureID  = glGetUniformLocation(programID, "myTextureSampler");

	// Read our .obj file
	std::vector<glm::vec3> vertices;
	std::vector<glm::vec2> uvs;
	std::vector<glm::vec3> normals;
	bool res = loadOBJ("suzanne.obj", vertices, uvs, normals);

	std::vector<unsigned short> indices;
	std::vector<glm::vec3> indexed_vertices;
	std::vector<glm::vec2> indexed_uvs;
	std::vector<glm::vec3> indexed_normals;
	indexVBO(vertices, uvs, normals, indices, indexed_vertices, indexed_uvs, indexed_normals);

	// Load it into a VBO

	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, indexed_vertices.size() * sizeof(glm::vec3), &indexed_vertices[0], GL_STATIC_DRAW);

	GLuint uvbuffer;
	glGenBuffers(1, &uvbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
	glBufferData(GL_ARRAY_BUFFER, indexed_uvs.size() * sizeof(glm::vec2), &indexed_uvs[0], GL_STATIC_DRAW);

	GLuint normalbuffer;
	glGenBuffers(1, &normalbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
	glBufferData(GL_ARRAY_BUFFER, indexed_normals.size() * sizeof(glm::vec3), &indexed_normals[0], GL_STATIC_DRAW);

	// Generate a buffer for the indices as well
	GLuint elementbuffer;
	glGenBuffers(1, &elementbuffer);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(unsigned short), &indices[0] , GL_STATIC_DRAW);



	// Generate positions & rotations for 100 monkeys
	std::vector<glm::vec3> positions(100);
	std::vector<glm::quat> orientations(100);
	for(int i=0; i<100; i++){
		positions[i] = glm::vec3(rand()%20-10, rand()%20-10, rand()%20-10);
		orientations[i] = glm::quat(glm::vec3(rand()%360, rand()%360, rand()%360));
	}




	// Get a handle for our "pickingColorID" uniform
	GLuint pickingColorID = glGetUniformLocation(pickingProgramID, "PickingColor");

	// Get a handle for our "LightPosition" uniform
	glUseProgram(programID);
	GLuint LightID = glGetUniformLocation(programID, "LightPosition_worldspace");

	// For speed computation
	double lastTime = glfwGetTime();
	int nbFrames = 0;

	do{

		// Measure speed
		double currentTime = glfwGetTime();
		nbFrames++;
		if ( currentTime - lastTime >= 1.0 ){ // If last prinf() was more than 1sec ago
			// printf and reset
			printf("%f ms/frame\n", 1000.0/double(nbFrames));
			nbFrames = 0;
			lastTime += 1.0;
		}


		// Compute the MVP matrix from keyboard and mouse input
		computeMatricesFromInputs();
		glm::mat4 ProjectionMatrix = getProjectionMatrix();
		glm::mat4 ViewMatrix = getViewMatrix();



		// PICKING IS DONE HERE
		// (Instead of picking each frame if the mouse button is down, 
		// you should probably only check if the mouse button was just released)
		if (glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_LEFT)){

			// Clear the screen in white
			glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
			glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
			glUseProgram(pickingProgramID);

			// Only the positions are needed (not the UVs and normals)
			glEnableVertexAttribArray(0);

			// Draw the 100 monkeys, each with a slighly different color
			for(int i=0; i<100; i++){


				glm::mat4 RotationMatrix = glm::toMat4(orientations[i]);
				glm::mat4 TranslationMatrix = translate(mat4(), positions[i]);
				glm::mat4 ModelMatrix = TranslationMatrix * RotationMatrix;

				glm::mat4 MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;

				// Send our transformation to the currently bound shader, 
				// in the "MVP" uniform
				glUniformMatrix4fv(PickingMatrixID, 1, GL_FALSE, &MVP[0][0]);

				// Convert "i", the integer mesh ID, into an RGB color
				int r = (i & 0x000000FF) >>  0;
				int g = (i & 0x0000FF00) >>  8;
				int b = (i & 0x00FF0000) >> 16;

				// OpenGL expects colors to be in [0,1], so divide by 255.
				glUniform4f(pickingColorID, r/255.0f, g/255.0f, b/255.0f, 1.0f);

				// 1rst attribute buffer : vertices
				glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
				glVertexAttribPointer(
					0,                  // attribute
					3,                  // size
					GL_FLOAT,           // type
					GL_FALSE,           // normalized?
					0,                  // stride
					(void*)0            // array buffer offset
				);

				// Index buffer
				glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);

				// Draw the triangles !
				glDrawElements(
					GL_TRIANGLES,      // mode
					indices.size(),    // count
					GL_UNSIGNED_SHORT,   // type
					(void*)0           // element array buffer offset
				);

			}

			glDisableVertexAttribArray(0);


			// Wait until all the pending drawing commands are really done.
			// Ultra-mega-over slow ! 
			// There are usually a long time between glDrawElements() and
			// all the fragments completely rasterized.
			glFlush();
			glFinish(); 


			glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

			// Read the pixel at the center of the screen.
			// You can also use glfwGetMousePos().
			// Ultra-mega-over slow too, even for 1 pixel, 
			// because the framebuffer is on the GPU.
			unsigned char data[4];
			glReadPixels(1024/2, 768/2,1,1, GL_RGBA, GL_UNSIGNED_BYTE, data);

			// Convert the color back to an integer ID
			int pickedID = 
				data[0] + 
				data[1] * 256 +
				data[2] * 256*256;

			if (pickedID == 0x00ffffff){ // Full white, must be the background !
				message = "background";
			}else{
				std::ostringstream oss;
				oss << "mesh " << pickedID;
				message = oss.str();
			}

			// Uncomment these lines to see the picking shader in effect
			//glfwSwapBuffers(window);
			//continue; // skips the normal rendering


		}


		// Dark blue background
		glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
		// Re-clear the screen for real rendering
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);


		// Use our shader
		glUseProgram(programID);

		glEnableVertexAttribArray(0);
		glEnableVertexAttribArray(1);
		glEnableVertexAttribArray(2);

		for(int i=0; i<100; i++){


			glm::mat4 RotationMatrix = glm::toMat4(orientations[i]);
			glm::mat4 TranslationMatrix = translate(mat4(), positions[i]);
			glm::mat4 ModelMatrix = TranslationMatrix * RotationMatrix;

			glm::mat4 MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;

			// Send our transformation to the currently bound shader, 
			// in the "MVP" uniform
			glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
			glUniformMatrix4fv(ModelMatrixID, 1, GL_FALSE, &ModelMatrix[0][0]);
			glUniformMatrix4fv(ViewMatrixID, 1, GL_FALSE, &ViewMatrix[0][0]);

			glm::vec3 lightPos = glm::vec3(4,4,4);
			glUniform3f(LightID, lightPos.x, lightPos.y, lightPos.z);

			// Bind our texture in Texture Unit 0
			glActiveTexture(GL_TEXTURE0);
			glBindTexture(GL_TEXTURE_2D, Texture);
			// Set our "myTextureSampler" sampler to use Texture Unit 0
			glUniform1i(TextureID, 0);

			// 1rst attribute buffer : vertices
			glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
			glVertexAttribPointer(
				0,                  // attribute
				3,                  // size
				GL_FLOAT,           // type
				GL_FALSE,           // normalized?
				0,                  // stride
				(void*)0            // array buffer offset
			);

			// 2nd attribute buffer : UVs
			glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
			glVertexAttribPointer(
				1,                                // attribute
				2,                                // size
				GL_FLOAT,                         // type
				GL_FALSE,                         // normalized?
				0,                                // stride
				(void*)0                          // array buffer offset
			);

			// 3rd attribute buffer : normals
			glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
			glVertexAttribPointer(
				2,                                // attribute
				3,                                // size
				GL_FLOAT,                         // type
				GL_FALSE,                         // normalized?
				0,                                // stride
				(void*)0                          // array buffer offset
			);

			// Index buffer
			glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);

			// Draw the triangles !
			glDrawElements(
				GL_TRIANGLES,      // mode
				indices.size(),    // count
				GL_UNSIGNED_SHORT,   // type
				(void*)0           // element array buffer offset
			);


		}

		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);
		glDisableVertexAttribArray(2);

		// Draw GUI
		TwDraw();

		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0 );

	// Cleanup VBO and shader
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteBuffers(1, &uvbuffer);
	glDeleteBuffers(1, &normalbuffer);
	glDeleteBuffers(1, &elementbuffer);
	glDeleteProgram(programID);
	glDeleteTextures(1, &Texture);
	glDeleteVertexArrays(1, &VertexArrayID);

	// Close OpenGL window and terminate GLFW
	glfwTerminate();

	return 0;
}