Why the triangle isn't showing on screen (OpenGL 3.3)? - c++

Question

I've tried all. Following OpenGL tutorials from http://www.opengl-tutorial.org/beginners-tutorials/.
On tutorial 4 it's asked to do a double model on your on. But I can't render the triangle and the cube at the same time (triangle doesn't appeared). Just did everything the same, changing the name of the variables related to the triangle. I didn't found in any other site the answers on this OPenGL 3.3 syntax, just found on completely different syntax (I don't want to change the way I do thins every time I found a error - it's like changing everything just after any error. For me doesn't make any sense).
Code it's a little big, but many of the things are just to open the Window and run the main loop (and the cube coordinates. They aren't a VBO. I'll learn later):
// Include standard headers
#include <stdio.h>
#include <stdlib.h>
// Include GLEW. Always include it before gl.h and glfw.h, since it's a bit magic.
#include <GL/glew.h>
// Include GLFW
#include <GL/glfw.h>
// Include GLM
#include <glm/glm.hpp>
#include "common/shader.hpp"
#include <iostream>
#include <glm/gtc/matrix_transform.hpp>
using namespace std;
using namespace glm;
// Include standard headers
#include <stdio.h>
#include <stdlib.h>
// Include GLEW
#include <GL/glew.h>
// Include GLFW
#include <GL/glfw.h>
// Include GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;
#include <common/shader.hpp>
int main(int argc, char *argv[] )
{
// Initialise GLFW
if( !glfwInit() )
{
fprintf( stderr, "Failed to initialize GLFW\n" );
return -1;
}
glfwOpenWindowHint(GLFW_FSAA_SAMPLES, 4); // 4x antialiasing
glfwOpenWindowHint(GLFW_OPENGL_VERSION_MAJOR, 3); // We want OpenGL 3.3
glfwOpenWindowHint(GLFW_OPENGL_VERSION_MINOR, 3);
glfwOpenWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); //We don't want the old OpenGL
// Open a window and create its OpenGL context
if( !glfwOpenWindow( 1024, 768, 0,0,0,0, 32,0, GLFW_WINDOW ) )
{
fprintf( stderr, "Failed to open GLFW window\n" );
glfwTerminate();
return -1;
}
// Initialize GLEW
if (glewInit() != GLEW_OK) {
fprintf(stderr, "Failed to initialize GLEW\n");
return -1;
}
// Enable depth test
glEnable(GL_DEPTH_TEST);
// Accept fragment if it closer to the camera than the former one
glDepthFunc(GL_LESS);
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);
// Create and compile our GLSL program from the shaders
GLuint programID = LoadShaders( "TransformVertexShader.vertexshader", "ColorFragmentShader.fragmentshader" );
//Perspective Matrix
// Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
mat4 Projection = perspective(45.0f, 4.0f/3.0f, 0.1f, 100.0f);
// Camera matrix
mat4 View = lookAt(
vec3(4,3,-3), // Camera is at (4,3,3), in World Space
vec3(0,0,0), // and looks at the origin
vec3(0,1,0) // Head is up (set to 0,-1,0 to look upside-down)
);
// Model matrix : an identity matrix (model will be at the origin)
mat4 Model = mat4(1.0f); // Changes for each model !
// Our ModelViewProjection : multiplication of our 3 matrices
mat4 MVP = Projection * View * Model; // Remember, matrix multiplication is the other way around
// Get a handle for our "MVP" uniform.
// Only at initialisation time.
GLuint MatrixID = glGetUniformLocation(programID, "MVP");
// Send our transformation to the currently bound shader,
// in the "MVP" uniform
// For each model you render, since the MVP will be different (at least the M part)
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
mat4 triangle_Model = mat4(1.0f);
mat4 triangle_MPV = Projection * View * triangle_Model;
GLuint triangle_MatrixID = glGetUniformLocation(programID, "MPV");
glUniformMatrix4fv(triangle_MatrixID, 1, GL_FALSE, &triangle_MPV[0][0]);
static const GLfloat triangle_buffer_data[] = {
-2.0f, -3.0f, 1.0f,
2.0f, -3.0f, 1.0f,
0.0f, 3.0f,-1.0f
};
// This will identify our vertex buffer
GLuint triangle_vertexbuffer;
// Generate 1 buffer, put the resulting identifier in vertexbuffer
glGenBuffers(1, &triangle_vertexbuffer);
// The following commands will talk about our 'vertexbuffer' buffer
glBindBuffer(GL_ARRAY_BUFFER, triangle_vertexbuffer);
// Give our vertices to OpenGL.
glBufferData(GL_ARRAY_BUFFER, sizeof(triangle_buffer_data), triangle_buffer_data, GL_STATIC_DRAW);
// Our vertices. Tree consecutive floats give a 3D vertex; Three consecutive vertices give a triangle.
// A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices
static const GLfloat g_vertex_buffer_data[] = {
-1.0f,-1.0f,-1.0f, // triangle 1 : begin
-1.0f,-1.0f, 1.0f,
-1.0f, 1.0f, 1.0f, // triangle 1 : end
1.0f, 1.0f,-1.0f, // triangle 2 : begin
-1.0f,-1.0f,-1.0f,
-1.0f, 1.0f,-1.0f, // triangle 2 : end
1.0f,-1.0f, 1.0f,
-1.0f,-1.0f,-1.0f,
1.0f,-1.0f,-1.0f,
1.0f, 1.0f,-1.0f,
1.0f,-1.0f,-1.0f,
-1.0f,-1.0f,-1.0f,
-1.0f,-1.0f,-1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f,-1.0f,
1.0f,-1.0f, 1.0f,
-1.0f,-1.0f, 1.0f,
-1.0f,-1.0f,-1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f,-1.0f, 1.0f,
1.0f,-1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f,-1.0f,-1.0f,
1.0f, 1.0f,-1.0f,
1.0f,-1.0f,-1.0f,
1.0f, 1.0f, 1.0f,
1.0f,-1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f,-1.0f,
-1.0f, 1.0f,-1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f,-1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f,-1.0f, 1.0f
};
// This will identify our vertex buffer
GLuint vertexbuffer;
// Generate 1 buffer, put the resulting identifier in vertexbuffer
glGenBuffers(1, &vertexbuffer);
// The following commands will talk about our 'vertexbuffer' buffer
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
// Give our vertices to OpenGL.
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);
// One color for each vertex. They were generated randomly.
static const GLfloat g_color_buffer_data[] = {
0.583f, 0.771f, 0.014f,
0.609f, 0.115f, 0.436f,
0.327f, 0.483f, 0.844f,
0.822f, 0.569f, 0.201f,
0.435f, 0.602f, 0.223f,
0.310f, 0.747f, 0.185f,
0.597f, 0.770f, 0.761f,
0.559f, 0.436f, 0.730f,
0.359f, 0.583f, 0.152f,
0.483f, 0.596f, 0.789f,
0.559f, 0.861f, 0.639f,
0.195f, 0.548f, 0.859f,
0.014f, 0.184f, 0.576f,
0.771f, 0.328f, 0.970f,
0.406f, 0.615f, 0.116f,
0.676f, 0.977f, 0.133f,
0.971f, 0.572f, 0.833f,
0.140f, 0.616f, 0.489f,
0.997f, 0.513f, 0.064f,
0.945f, 0.719f, 0.592f,
0.543f, 0.021f, 0.978f,
0.279f, 0.317f, 0.505f,
0.167f, 0.620f, 0.077f,
0.347f, 0.857f, 0.137f,
0.055f, 0.953f, 0.042f,
0.714f, 0.505f, 0.345f,
0.783f, 0.290f, 0.734f,
0.722f, 0.645f, 0.174f,
0.302f, 0.455f, 0.848f,
0.225f, 0.587f, 0.040f,
0.517f, 0.713f, 0.338f,
0.053f, 0.959f, 0.120f,
0.393f, 0.621f, 0.362f,
0.673f, 0.211f, 0.457f,
0.820f, 0.883f, 0.371f,
0.982f, 0.099f, 0.879f
};
GLuint colorbuffer;
glGenBuffers(1, &colorbuffer);
glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);
glfwSetWindowTitle( "Tutorials" );
// Dark blue background
glClearColor(0.0f, 0.0f, 0.3f, 0.0f);
// Ensure we can capture the escape key being pressed below
glfwEnable( GLFW_STICKY_KEYS );
//main loop
do{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Use our shader
glUseProgram(programID);
//First Attribute: Draw a Cube
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(
0, // attribute 0. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// 2nd attribute buffer : colors
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
glVertexAttribPointer(
1, // attribute. No particular reason for 1, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// Draw the triangle !
glDrawArrays(GL_TRIANGLES, 0, 12*3); // 12*3 indices starting at 0 -> 12 triangles -> 6 squares
glDisableVertexAttribArray(0);
//3rd attribute: draw a triangle
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, triangle_vertexbuffer);
glVertexAttribPointer(
2,
3,
GL_FLOAT,
GL_FALSE,
0,
(void*)0
);
glDrawArrays(GL_TRIANGLES,0,3);
glDisableVertexAttribArray(2);
// Send our transformation to the currently bound shader,
// in the "MVP" uniform
// For each model you render, since the MVP will be different (at least the M part)
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(triangle_MatrixID, 1 ,GL_FALSE, &triangle_MPV[0][0]);
// Swap buffers
glfwSwapBuffers();
} // Check if the ESC key was pressed or the window was closed
while( glfwGetKey( GLFW_KEY_ESC ) != GLFW_PRESS &&
glfwGetWindowParam( GLFW_OPENED ) );
glfwTerminate();
// Cleanup VBO
glDeleteBuffers(1, &vertexbuffer);
glDeleteVertexArrays(1, &VertexArrayID);
glDeleteBuffers(1, &triangle_vertexbuffer);
glDeleteBuffers(1, &colorbuffer);
return EXIT_SUCCESS;
}
And, I don't think that this is the problem (tutorial said that it needed 1 shader and on the cube it worked perfectly), but I'll post the shaders code here too:
Collor Fragment shader:
#version 330 core
// Interpolated values from the vertex shaders
in vec3 fragmentColor;
// Ouput data
out vec3 color;
void main(){
// Output color = color specified in the vertex shader,
// interpolated between all 3 surrounding vertices
color = fragmentColor;
}
TransformVertexShadder:
#version 330 core
// Input vertex data, different for all executions of this shader.
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec3 vertexColor;
// Output data ; will be interpolated for each fragment.
out vec3 fragmentColor;
// Values that stay constant for the whole mesh.
uniform mat4 MVP;
void main(){
// Output position of the vertex, in clip space : MVP * position
gl_Position = MVP * vec4(vertexPosition_modelspace,1);
// The color of each vertex will be interpolated
// to produce the color of each fragment
fragmentColor = vertexColor;
}
Can anyone help-me?

Answer 1

I don't think you can output the fragment color as a vec3, I use vec4(color, 1.0) in most cases.