Multisample textures

I assume your vertex shader has the texture coordinate in defined as a vec3?

Quote:

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Originally Posted by tonyo_au

I assume your vertex shader has the texture coordinate in defined as a vec3?

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yes.
Vertex shader:

Code :

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in vec3 inputtexcoord;
in vec3 tk_position;
out vec3 ps_texCoord;
 
uniform mat4 tk_mvpMatrix;
void main(void)
{
        ps_texCoord = inputtexcoord;
gl_Position = tk_mvpMatrix * vec4(tk_position, 1.0); 
}

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fragement

Code :

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uniform sampler2DMS tk_diffuseMap;
in vec3 ps_texCoord;
out vec4 fragColor;
 
void main(void)
{
 
	vec2 iTmp = textureSize(tk_diffuseMap);
	vec2 tmp =floor(iTmp * ps_texCoord.xy);
 
	vec4 color;
	for(int i = 0; i < 4; ++i)
	{
		color = color + texelFetch(tk_diffuseMap, ivec2(ps_texCoord), i);
	}
 
fragColor=vec4(color/4);
}

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Sorry I should have seen this earlier

texelFetch texture coordinates are in pixels not 0-1; so you need to multiply uv by texture width and height

Quote:

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Originally Posted by tonyo_au

Sorry I should have seen this earlier

texelFetch texture coordinates are in pixels not 0-1; so you need to multiply uv by texture width and height

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There was a mistake in above frag shader: for
texelFetch(tk_diffuseMap, ivec2(ps_texCoord), i);


Now,
vec2 iTmp = textureSize(tk_diffuseMap);
vec2 tmp =floor(iTmp * ps_texCoord.xy);
color = color + texelFetch(tk_diffuseMap, ivec2(tmp), i);

this also not working.

When I have errors like this that I can't understand I modify the frag shader to display the uv values, eg

Code :

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fragColor=vec4(ps_texCoord.xy,0,1);
fragColor=vec4(ps_texCoord.x,0,0,1); // to just see the u  values

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Now you can see how the texture is being mapped onto the cube. It may give a clue as to what is wrong

Quote:

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Originally Posted by tonyo_au

When I have errors like this that I can't understand I modify the frag shader to display the uv values, eg

Code :

---

 
fragColor=vec4(ps_texCoord.xy,0,1);
fragColor=vec4(ps_texCoord.x,0,0,1); // to just see the u  values

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Now you can see how the texture is being mapped onto the cube. It may give a clue as to what is wrong

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Many thanks for your help..
Got it working..

Great to here;)

When using multisampled textures, do i need to set samplers ( to number which i am using in glTexImage2DMultisample ) ? because i am assuming it needs to be set in MSAA. Please correct me if wrong. I have no idea how internally multisampling works..

When just reading from multisample textures in a shader (what it sounds like you want to do), you can forget anything you might know (or not know) about multisample rasterization -- it doesn't matter. Conceptually you just have a texture where instead of having 1 vector value per pixel you have N vector values per pixel, where N is the number of samples per pixel you allocated for that multisample texture.

To fetch the Nth sample from a particular pixel, just bind the multisample texture handle (what you get from glGenTextures) to a texture unit, and then in the shader, call texelFetch with the integer texcoord ("P") addressing the specific pixel and the "sample" argument being the sample index within that pixel.

Quote:

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Originally Posted by Dark Photon

When just reading from multisample textures in a shader (what it sounds like you want to do), you can forget anything you might know (or not know) about multisample rasterization -- it doesn't matter. Conceptually you just have a texture where instead of having 1 vector value per pixel you have N vector values per pixel, where N is the number of samples per pixel you allocated for that multisample texture.

To fetch the Nth sample from a particular pixel, just bind the multisample texture handle (what you get from glGenTextures) to a texture unit, and then in the shader, call texelFetch with the integer texcoord ("P") addressing the specific pixel and the "sample" argument being the sample index within that pixel.

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Thanks, I mean to say do i need to set number of samples to 4 or 8 (instead of 1) while creating context in my config attributes?