Framebuffer depth-artifacts - c++

Question

There's some Artifacts on my FrameBuffer Depth Texture I can't get rid off:
The Code used to init the FrameBuffer:
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glGenTextures(1, &color);
glBindTexture(GL_TEXTURE_2D, color);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, DISPLAY_WIDTH, DISPLAY_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glGenTextures(1, &depth);
glBindTexture(GL_TEXTURE_2D, depth);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, DISPLAY_WIDTH, DISPLAY_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glFramebufferTexture(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, color, 0);
glFramebufferTexture(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, depth, 0);
GLuint attachments[2] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1};
glDrawBuffers(2, attachments);
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
std::cout << "FBO FEHLER" << std::endl;
}
Code used to draw the FrameBuffer:
shader->bind();
// Bind Textures
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, color);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, depth);
glUniform1i(shader->getUniform("tex"), 0);
glUniform1i(shader->getUniform("depth"), 1);
glUniformMatrix4fv(shader->getUniform("matrix"), 1, GL_FALSE, glm::value_ptr(ortho));
// Draw Call
glBindBuffer(GL_ARRAY_BUFFER,fbovbo);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 20, (void*)0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 20, (void*)12);
glDrawArrays(GL_TRIANGLE_STRIP,0,4);
glBindBuffer(GL_ARRAY_BUFFER, 0);
// Unbind
shader->unbind();//*/
FragmentShader of the actual rendering:
#version 330 core
layout(location = 0) out vec4 out_color;
layout(location = 1) out vec4 out_depth;
in float temp;
void main(void){
out_color = vec4(1,0.0,0.0,1.0);
out_depth = vec4(gl_FragCoord.z);
}
FragmentShader of the FrameBuffer rendering:
#version 330 core
in vec2 fuv;
out vec4 color;
uniform sampler2D tex;
uniform sampler2D depth;
void main(){
vec4 d = texture2D(depth, fuv);
gl_FragDepth = d.a;
vec4 c = texture2D(tex,fuv);
if(c.a<0.1){
discard;
}
color = c;
//color = vec4(texture2D(depth, fuv).zzz,1.0);
//color.a = 0.8;
//color = vec4(1,0,0,0.5);
}
The red "Mesh" is behind the brown surface, but its borders still appear. thats the problem

Answer 1

The problem might come from the limited precision of the depth buffer. Basically, the range between near and farplane has to be represented by the depth-buffer. In your case, the depth-buffer has 8 bit, thus there are only 256 different depth values that can be represented. When two objects are closer together than this, they will be mapped to the same value in the depth buffer.
To overcome this, you can try to increase the precision of the depth buffer, for example, by using
glGenTextures(1, &depth);
glBindTexture(GL_TEXTURE_2D, depth);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16, DISPLAY_WIDTH, DISPLAY_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_SHORT, NULL);
Side-note: I'm not sure why the depth texture has four channels. If you don't need them, I would change this to a one channel format.