How to bind a GL_TEXTURE_2D_ARRAY to a framebuffer on GL_COLOR_ATTACHMENT1?

Question

Edit : see @Rabbid76 answer, question was not truly related to GL_TEXTURE_2D_ARRAY, only to framebuffer color attachment activation!

I'm having trouble updating a shader that use to ouput into a single texture to multiple textures. Here's the simplified code, I'll put all I find relevant, feel free to ask for other parts of the code if they are important.

glGenTexture(1, tex);
glBindTexture(GL_TEXTURE_2D_ARRAY, tex);
glTexStorage3D(GL_TEXTURE_2D_ARRAY, 1, GL_RGBA32F, x, y, 2);

glGenFramebuffers(1, &FBO);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
glFramebufferTextureLayer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, tex, 0, 0);
glFramebufferTextureLayer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, tex, 0, 1);

frag shader that writes :

#version 330

layout(location = 0) out vec4 col1;
layout(location = 1) out vec4 col2;

int main()
{
    col1 = vec4(1.0);
    col2 = vec4(2.0);
}

other shader that uses the result :

#version 330 core

uniform sampler2DArray tex;

in vec2 Coord;

int main()
{
    vec4 val = texture(tex, vec3(Coord, 0));
    val += texture(tex, vec3(Coord, 1));
}

The problem is that col1 is well written in layout 0 (regardless of texture layer, glFramebufferTextureLayer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, texDefo, 0, 1); works as well), but I don't get to write in layout 1 (GL_COLOR_ATTACHMENT1). Am I missing something here ?

Extensive tests :

From what I could narrow it down to, it really looks like layout(location = 1) doesn't work how I would have expected. With the code provided I get

• val = col1 when layout(location = 0) out vec4 col1;
• val = col2 when layout(location = 0) out vec4 col2; both regarless which texture layer I did bind the GL_COLOR_ATTACHMENTi, ie both layers seems to work in the GL_TEXTURE_2D_ARRAY.

Answer 1

You need to specify the buffers to be drawn into with glDrawBuffers:

GLenum drawBuffers[]{ GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1 };
glDrawBuffers(2, drawBuffers);