Regarding drawBuffer in glClearBufferiv

[debonair]

I am rendering geometry on non default FBO and applying it as integer texture to the geometry rendered on default FBO. To clear a color on non default FBO, i am using glClearBufferiv() call. I am not getting what is drawBuffer (2nd argument) in my case. I tried with 0, but its not working. it does not clear the color.

GLint cl[]={32000,32000,32000,32767};
glClearBufferiv(GL_COLOR, 0, cl);
 
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
My frag shader:
 
out ivec4 fragColor;
 
void main()
{
fragColor = ivec4(0,32767,0,32767);
}

With this, it renders green geometry but the outside color is black.

[aqnuep]

The drawbuffer parameter must be the drawbuffer index, i.e. an index into the array of draw buffers specified through glDrawBuffers.

E.g.:

GLenum drawbuffers[] = { GL_COLOR_ATTACHMENT3, GL_COLOR_ATTACHMENT1 };
glDrawBuffers(2, drawbuffers);
glClearBuffer*(GL_COLOR, 0, color); // clears GL_DRAW_BUFFER0, i.e. GL_COLOR_ATTACHMENT3
glClearBuffer*(GL_COLOR, 1, color); // clears GL_DRAW_BUFFER1, i.e. GL_COLOR_ATTACHMENT1

It works the exact same way with the default FBO, just the draw buffer enums are different there.

E.g.

GLenum drawbuffers[] = { GL_FRONT, GL_BACK };
glDrawBuffers(2, drawbuffers);
glClearBuffer*(GL_COLOR, 0, color); // clears GL_DRAW_BUFFER0, i.e. GL_FRONT
glClearBuffer*(GL_COLOR, 1, color); // clears GL_DRAW_BUFFER1, i.e. GL_BACK

You probably forgot to call glDrawBuffers.

[debonair]

The drawbuffer parameter must be the drawbuffer index, i.e. an index into the array of draw buffers specified through glDrawBuffers.

E.g.:

GLenum drawbuffers[] = { GL_COLOR_ATTACHMENT3, GL_COLOR_ATTACHMENT1 };
glDrawBuffers(2, drawbuffers);
glClearBuffer*(GL_COLOR, 0, color); // clears GL_DRAW_BUFFER0, i.e. GL_COLOR_ATTACHMENT3
glClearBuffer*(GL_COLOR, 1, color); // clears GL_DRAW_BUFFER1, i.e. GL_COLOR_ATTACHMENT1

It works the exact same way with the default FBO, just the draw buffer enums are different there.

E.g.

GLenum drawbuffers[] = { GL_FRONT, GL_BACK };
glDrawBuffers(2, drawbuffers);
glClearBuffer*(GL_COLOR, 0, color); // clears GL_DRAW_BUFFER0, i.e. GL_FRONT
glClearBuffer*(GL_COLOR, 1, color); // clears GL_DRAW_BUFFER1, i.e. GL_BACK

You probably forgot to call glDrawBuffers.

Thanks for your reply.
I did this:

GLenum buffers[] = { GL_COLOR_ATTACHMENT0};
glDrawBuffers(1,buffers);
GLint cl[]={32000,32000,32000,32767};
glClearBufferiv(GL_COLOR, 0, cl);

I am binding non default fbo and then while rendering on it i put above calls. My non default FBO has color (GL_COLOR_ATTACHMENT0) and depth attachment.
I dont understand what is wrong with above code.. Is it a driver bug?

[aqnuep]

From what you've described it could be a driver bug (assuming there are no errors in the rest of the code).

[Dan Bartlett]

What is that glClear call with GL_COLOR_BUFFER_BIT included doing in your original post? Was that just a copy/paste error?

[debonair]

What is that glClear call with GL_COLOR_BUFFER_BIT included doing in your original post? Was that just a copy/paste error?

Ok, i got it.. I removed glClear(GL_COLOR_BUFFER_BIT); and now it is working. I dont get it i was thinking that glclearbuffer will only set values for clearing buffer but actually glClear(GL_COLOR_BUFFER_BIT); it will clear out color values.

Now, there is one problem. I have GL_RGBA16I as internal format type. now when i clear buffer with {0,50,50,32767} it sets G B bits to max values even if they are 50. What is problem here?

[Alfonse Reinheart]

The problem is how you're reading the data. So... how are you reading the data?

[debonair]

The problem is how you're reading the data. So... how are you reading the data?

I am doing this stuff on newly created FBO and attaching it color attachment. I am applying this texture on geometry rendered on system default FBO.
So basically, I have these calls:

glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, 1 ,GL_RGBA16I, 32, 32,true);
glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER,GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D_MULTISAMPLE,id1,0);

and frag shader mentioned above for rendering on newly created FBO.

[Alfonse Reinheart]

There seems to have been a failure to communicate.

You are rendering to an integer texture. Then you are reading from that integer texture, either via a sampler in a later rendering operation or with glReadPixels/glGetTexImage.

I'm not asking about how you're setting up your FBO and rendering to it. I'm asking about how you're reading the data and thus determining that "it sets G B bits to max values" has happened. I want to see the code wherein you are making that determination.

[debonair]

There seems to have been a failure to communicate.

You are rendering to an integer texture. Then you are reading from that integer texture, either via a sampler in a later rendering operation or with glReadPixels/glGetTexImage.

I'm not asking about how you're setting up your FBO and rendering to it. I'm asking about how you're reading the data and thus determining that "it sets G B bits to max values" has happened. I want to see the code wherein you are making that determination.

ok, here is my frag shader for reading that texture:

uniform isampler2DMS tk_diffuseMap;
in vec3 ps_texCoord;
out vec4 fragColor;
uniform int samples;
uniform int factor; 
void main(void)
{
 
	vec2 iTmp = textureSize(tk_diffuseMap);
	vec2 tmp =floor(iTmp * ps_texCoord.xy);
	ivec4 temp;	 
	vec4 temp1;
	vec4 color;
 
	for(int i = 0; i < samples; ++i)
	{
		 temp= texelFetch(tk_diffuseMap, ivec2(tmp), i);
		 temp1=vec4(temp);
		 temp1=temp1/32767;
		color = color +	temp1;
	}
 
	fragColor = vec4(color/samples);
}

i am dividing that by 32767 for normalizing the data as my type is GL_RGBA16I..