I'm rendering to texture,but renderbuffer is black - c++

Question

I'm trying to render to texture.Using opengl-es 2.0.I wanna make Black and white postprocessing.But all I see, is black texture.On scene I have lightsources, and two spheres.But when I'm trying to render my texture that attached to framebuffer, I see black square.
this->frameBuffersCount = 3;
this->frameBuffers = new int[frameBuffersCount];
glGenFramebuffers(frameBuffersCount, (GLuint*)this->frameBuffers);
this->texturesCount = this->frameBuffersCount * 2;
this->bufferTextures = new int[this->texturesCount];
glGenTextures(this->texturesCount, (GLuint*)this->bufferTextures);
for(int i = 0; i < this->texturesCount / 2; ++i)
{
glBindTexture(GL_TEXTURE_2D, this->bufferTextures[2*i]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, screenWidth, screenHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glBindTexture(GL_TEXTURE_2D,0);
glBindTexture(GL_TEXTURE_2D, this->bufferTextures[2*i + 1]);
glTexImage2D(GL_TEXTURE_2D, 0,GL_DEPTH_COMPONENT, screenWidth, screenHeight, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glBindTexture(GL_TEXTURE_2D,0);
}
for(int i = 0; i < this->frameBuffersCount; ++i)
{
glBindFramebuffer(GL_FRAMEBUFFER, this->frameBuffers[i]);
glFramebufferTexture2D(GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0,
GL_TEXTURE_2D,
this->bufferTextures[2*i],
0);
glFramebufferTexture2D(GL_FRAMEBUFFER,
GL_DEPTH_ATTACHMENT,
GL_TEXTURE_2D,
this->bufferTextures[2*i + 1],
0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
this->ordinaryQuad = new ModelVertex[4];
this->ordinaryQuad[0].UV = Vector2(0.0,0.0);
this->ordinaryQuad[0].position = Vector3(-1, -1, 0.0);
this->ordinaryQuad[1].UV = Vector2(0.0,1.0);
this->ordinaryQuad[1].position = Vector3(-1.0, 1.0, 0.0);
this->ordinaryQuad[2].UV = Vector2(1.0,1.0);
this->ordinaryQuad[2].position = Vector3(1.0, 1.0, 0.0);
this->ordinaryQuad[3].UV = Vector2(1.0,0.0);
this->ordinaryQuad[3].position = Vector3(1.0, -1.0, 0.0);
This is rendering code.
void EffectManager::applyBnW()
{
glBindFramebuffer(GL_FRAMEBUFFER, this->frameBuffers[0]);
auto res = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if(res == GL_FRAMEBUFFER_COMPLETE)
{
SceneManager::GetInstance().DrawScene();
glDisable(GL_DEPTH_TEST);
unsigned short indices[6] = {0,2,1,2,0,3};
Shaders shaders;
shaders.Init("../Resources/Shaders/BlackAndWhiteVS.vs", "../Resources/Shaders/BlackAndWhiteFS.fs", 0);
glUseProgram(shaders.program);
unsigned int hVBuff,hInBuff;
glGenBuffers(1, &hVBuff);
glGenBuffers(1, &hInBuff);
glBindBuffer(GL_ARRAY_BUFFER, hVBuff);
glBufferData(GL_ARRAY_BUFFER, 4 * sizeof(SEngine::ModelVertex), this->ordinaryQuad, GL_STATIC_DRAW);
//glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, hInBuff);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, 6 * sizeof(unsigned short), indices, GL_STATIC_DRAW);
//glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, this->bufferTextures[0]);
glGenerateMipmap(GL_TEXTURE_2D);
if(shaders.positionAttribute != -1)
{
glEnableVertexAttribArray(shaders.positionAttribute);
glVertexAttribPointer(shaders.positionAttribute, 3, GL_FLOAT, GL_FALSE, sizeof(SEngine::ModelVertex), 0);
}
if(shaders.UVAttribute != -1)
{
glEnableVertexAttribArray(shaders.UVAttribute);
glVertexAttribPointer(shaders.UVAttribute, 2, GL_FLOAT, GL_FALSE, sizeof(SEngine::ModelVertex), (void*)(sizeof(Vector3)));
}
if(shaders.samplerUniform != -1)
{
glUniform1i(shaders.samplerUniform, 0);
}
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (void*)0);
//glDrawArrays(GL_TRIANGLES,0,4);
}
What is wrong?

Answer 1

Not a clear answer can be given since there is not enough information/code provided in your question.
Did you clear the depth buffer ?
When you generated the color in the fragment shader for the rendered objects, did you correctly calculate the White color?
One way I do in these situations to help me debug the issue is to remove potential error areas.
Clear the framebuffer to Red color and Alpha channel = 1.0
Clear depth buffer
Hard code gl_FragColor to vec4(1,1,1,1)
By doing this you can see if the output is all red? Then the issue is with the object rendering, such as transformation, clipping, depth rejection or other reason.
If you can see the objects with White color? Then you know it's the issue with your fragment shader
I would also recommend you to remove the line
glGenerateMipmap(GL_TEXTURE_2D);
As from what I can see in your code, it does not add any extra. If not this is the root-cause to your error.
Generating mipmaps on the texture that still being used and attached to a framebuffer object is not very effecient, especially if the driver internally would have to reallocate the memory for being able to store the new mipmap levels.

Answer 2

Solved.It was problems with index buffer and I forget to disable depth_test.