I have a code that initially had one shader (ourShader), one VAO and one VBO. It would render a scene with a textured cube and its reflection on the ground using Stencil testing. Now, I wanted to add a framebuffer for post-processing so I needed a second shader. I added a second shader (screenShader) and a second VBO. I don't use them in my drawing yet, but the simple fact that I'm adding them makes my code render a black, red triangle instead of the usual scene.
My code looks like this :
Shader ourShader(string("core.vs"), string("core.frag")); // shader class creating a shader program from vertex shader and fragment shader source files.
Shader screenShader(string("core2.vs"), string("core2.frag"));
// Setting up attributes, VAO, VBO
GLuint VAO;
array<GLuint, 2> VBO;
glGenVertexArrays(1, &VAO);
glGenBuffers(2, &VBO[0]);
glBindVertexArray(VAO);
// Data for first shader and first VBO
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(verticesCube), verticesCube, GL_STATIC_DRAW);
GLint posAttribLoc = glGetAttribLocation(ourShader.Program, "position");
glVertexAttribPointer(posAttribLoc, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)0); // specify (to the active VAO) how to retrieve the values for the attribute "position" from the data stored ("vertices" here) on the active VBO (GPU)
glEnableVertexAttribArray(posAttribLoc); // enable attribute for rendering
GLint colAttribLoc = glGetAttribLocation(ourShader.Program, "color");
glVertexAttribPointer(colAttribLoc, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
glEnableVertexAttribArray(colAttribLoc);
GLint texAttribLoc = glGetAttribLocation(ourShader.Program, "texCoord");
glVertexAttribPointer(texAttribLoc, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(6 * sizeof(GLfloat)));
glEnableVertexAttribArray(texAttribLoc);
// ##### PART GIVING A WEIRD RESULT #####
// Data for second shader and second VBO
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(verticesRectangle), verticesRectangle, GL_STATIC_DRAW);
GLint posAttribLoc2 = glGetAttribLocation(screenShader.Program, "position");
glVertexAttribPointer(posAttribLoc2, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)0); // specify (to the active VAO) how to retrieve the values for the attribute "position" from the data stored ("vertices" here) on the active VBO (GPU)
glEnableVertexAttribArray(posAttribLoc2); // enable attribute for rendering
GLint texAttribLoc2 = glGetAttribLocation(screenShader.Program, "texCoord");
glVertexAttribPointer(texAttribLoc2, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)(2 * sizeof(GLfloat)));
glEnableVertexAttribArray(texAttribLoc2);
// ##### END #####
// Setting up texture that will be used for the first shader
GLuint texture;
int width, height;
glGenTextures(1, &texture);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture); // makes "texture" the current texture and attaches it to texture unit 0
// Set the wrapping
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
// Set the filtering
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
unsigned char* image = SOIL_load_image("res/images/image1.jpg", &width, &height, 0, SOIL_LOAD_RGBA);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image);
glGenerateMipmap(GL_TEXTURE_2D);
SOIL_free_image_data(image);
// Unbind VBO, texture before main loop
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindTexture(GL_TEXTURE_2D, 0);
glfwSwapInterval(1);
glfwSetKeyCallback(window, Input::keyCallback); // Input is a singleton class handling inputs. It works well.
glfwSetCursorPosCallback(window, Input::mouseCallback);
glfwSetScrollCallback(window, Input::scrollCallback);
while (glfwWindowShouldClose(window) == GLFW_FALSE) {
// MAIN LOOP
// ...
}
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(2, &VBO[0]);
The mainloop is not important I think. What I want to say is that if I remove the few lines dealing with the the second VBO, then the scene renders well. Otherwise, I get a weird-colored triangle.
And my two shaders use those source files for their respective vertex shader and fragment shader. By the way, I get no compilation errors from my shaders.
core.vs :
#version 330 core
in vec3 position;
in vec2 texCoord;
in vec3 color;
out vec2 TexCoord;
out vec3 Color;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
void main()
{
gl_Position = projection*view*model*vec4(position, 1.0);
TexCoord = vec2(texCoord.x, 1.0 - texCoord.y);
Color = color;
}
core.frag :
#version 330 core
in vec2 TexCoord;
in vec3 Color;
out vec4 outColor;
uniform sampler2D ourTexture0;
void main()
{
outColor = vec4(Color, 1)*texture(ourTexture0, TexCoord);
}
core2.vs :
#version 330 core
in vec2 position;
in vec2 texCoord;
out vec2 TexCoord;
void main()
{
gl_Position = vec4(position, 0.0, 1.0);
TexCoord = texCoord;
}
core2.frag :
#version 330 core
in vec2 TexCoord;
out vec4 outColor;
uniform sampler2D texFramebuffer;
void main()
{
outColor = texture(texFramebuffer, TexCoord);
}
The vertices look like this (but only the way to read them is important) :
GLfloat verticesRectangle[] = {
// position // texture coordinates
-0.5f, -0.5f, 0.0f, 0.0f,
0.5f, -0.5f, 1.0f, 0.0f,
-0.5f, 0.5f, 0.0f, 1.0f,
0.5f, 0.5f, 1.0f, 1.0f
};
GLfloat verticesCube[] = {
// position // color // texture coordinates
-0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
-0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
-0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f,
-1.0f, -0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, // reflection surface // not a part of the cube itself
-1.0f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 1.0f, 1.0f,
1.0f, -0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f,
1.0f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f,
-1.0f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 1.0f, 1.0f,
1.0f, -0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f
};
I've already looked at Binding a second vertex buffer seems to spoil my first vertex buffer, OpenGL OES ios 5.1 but the person had this problem because he didn't use his VAO correctly.
