Displaying Models in OpenGL C++ - c++

Question

|Actually, I am trying to display two or more models on the screen at the same time. I am generating three different vertex buffers for vertices, colors, normals separately, here is the main code:
//==================From here is my implementation ==========================//
// Create and compile our GLSL program from the shaders. Todo: load shader
GLuint programID = LoadShaders("simple_shading.vertexshader", "simple_shading.fragmentshader");
// Get a handle for uniform variables such as matrices, lights, ....
GLuint ModelMatrixID = glGetUniformLocation(programID, "ModelMatrix");
GLuint ViewMatrixID = glGetUniformLocation(programID, "ViewMatrix");
GLuint NormalMatrixID = glGetUniformLocation(programID, "NormalMatrix");
GLuint lightPosition_worldspaceID = glGetUniformLocation(programID, "lightPosition_worldspace");
GLuint lightColorID = glGetUniformLocation(programID, "lightColor");
// Get a handle for vertex attribute arrays such as vertex positions, colors, normals, ....
GLuint vertexPosition_modelspaceID = glGetAttribLocation(programID, "vertexPosition_modelspace");
GLuint vertexColorID = glGetAttribLocation(programID, "vertexColor");
GLuint vertexNormal_modelspaceID = glGetAttribLocation(programID, "vertexNormal_modelspace");
// Load your scene
TRIModel model;
TRIModel model2;
model.loadFromFile("models/ball.tri");
model2.loadFromFile("models/ball.tri");
//vector<TRIModel> models;
/*** Here shows an exmple which generates three different vertex buffers for vertices, colors, normals.***/
//However, you can always incorporate them together in a single buffer.(Hint: use glBufferSubData)
GLuint vertexbuffer;
glGenBuffers(1, &vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, model.vertices.size() * sizeof(vec3), &model.vertices[0], GL_STATIC_DRAW);
GLuint colorbuffer;
glGenBuffers(1, &colorbuffer);
glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
glBufferData(GL_ARRAY_BUFFER, model.vertices.size() * sizeof(vec3), &model.foreColors[0], GL_STATIC_DRAW);
GLuint normalbuffer;
glGenBuffers(1, &normalbuffer);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glBufferData(GL_ARRAY_BUFFER, model.vertices.size() * sizeof(vec3), &model.normals[0], GL_STATIC_DRAW);
///*** **/
GLfloat rotZ;
while (!glfwWindowShouldClose(window))
{
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// //Tell OpenGL to use the shader program
glUseProgram(programID);
// //send matrix to shader: You can use the keyboard and mouse to close the window and control the transformation
// // (See computeMatricesFromKey(window) )
mat4 ModelMatrix;
mat4 ViewMatrix = lookAt( vec3(0.5, 0.5, 1), vec3(2, 3, 2), vec3(0, 1.0, 0.0) );
//move object to the world origin
ModelMatrix = translate(mat4(1.0), -vec3(model.center[0], model.center[1], model.center[2]));
ModelMatrix = scale( ModelMatrix, vec3(0.002, 0.002, 0.002) );
ModelMatrix = rotate( ModelMatrix, rotZ, vec3(0.0, 0.0, 1.0) );
mat4 NormalMatrix = transpose( inverse(ViewMatrix * ModelMatrix) );
glUniformMatrix4fv(ViewMatrixID, 1, GL_FALSE, &ViewMatrix[0][0]);
glUniformMatrix4fv(ModelMatrixID, 1, GL_FALSE, &ModelMatrix[0][0]);
glUniformMatrix4fv(NormalMatrixID, 1, GL_FALSE, &NormalMatrix[0][0]);
// //send lights to shader
vec3 lightPosition = vec3(4, 4, 4);
vec3 lightColor = vec3(1.0, 1.0, 1.0);
glUniform3f(lightPosition_worldspaceID, lightPosition.x, lightPosition.y, lightPosition.z);
glUniform3f(lightColorID, lightColor.r, lightColor.g, lightColor.b);
//define an vertex attribute array on the vertex buffer
glEnableVertexAttribArray(vertexPosition_modelspaceID);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(
vertexPosition_modelspaceID, // The attribute we want to configure
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*) 0 // array buffer offset
);
// //define an vertex attribute array on the color buffer
glEnableVertexAttribArray(vertexColorID);
glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
glVertexAttribPointer(
vertexColorID, // The attribute we want to configure
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*) 0 // array buffer offset
);
// //define an vertex attribute array on the normal buffer
glEnableVertexAttribArray(vertexNormal_modelspaceID);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glVertexAttribPointer(
vertexNormal_modelspaceID, // The attribute we want to configure
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*) 0 // array buffer offset
);
//draw the scene by vertex attribute arrays
glDrawArrays(GL_TRIANGLES, 0, model.vertices.size());
glDisableVertexAttribArray(vertexPosition_modelspaceID);
glDisableVertexAttribArray(vertexColorID);
glDisableVertexAttribArray(vertexNormal_modelspaceID);
glfwSwapBuffers(window);
glfwPollEvents();
//
// //update rotate angle
rotZ += 0.1;
}
//// Cleanup VBO and shade //glDeleteBuffers(1, &vertexbuffer);
glDeleteBuffers(1, &colorbuffer);
glDeleteBuffers(1, &normalbuffer);
glDeleteProgram(programID);
//=================== implementation Ends here ================================//
I read in some resources that I can incorporate them together in a single buffer using glBufferSubData, but I dont know how to use it. eventually, I have successfully displayed one model as shown in the picture. Now, if I need to display another model, lets say I want to display another ball on the right side, what should I do? I tried to generate a nother set of buffers , but it is still not working. what I can see is just model one. Any ideas?