CODEWITHSUNDEEP
openglglslshaderblur
RobinCirex
RobinCirex

Reputation: 43

GLSL blur effect on non textured rect

I'm trying to get a blur working using a glsl shader. I have looked for it on the internet but found only found fragment shaders with a texture input. What if I want to blur things without a texture though? How would I do that?

Should look something like that:

img

Upvotes: 1

Views: 1169

Answers (1)

Yakov Galka
Yakov Galka

Reputation: 72539

A shader cannot read from a framebuffer directly. Textures are the primary way for reading images from within a shader (there's also SSBO but I wouldn't suggest using it here).

Thus, put it short, the answer to "how to blur an image without a texture" is: create a texture! You can either copy your image from the framebuffer to the texture with glCopyTextureSubImage2D; or, even better, render to an off-screen FBO backed by the texture from the start.

EDIT: example of copying from current framebuffer to a texture (in C):

GLuint tex;
glCreateTextures(GL_TEXTURE_2D, 1, &tex);
glTextureStorage2D(tex, 1 /*levels*/, GL_SRGB8_ALPHA8, width, height);
glCopyTextureSubImage2D(tex, 0, 0, 0, 0, 0, width, height);
// tex now contains the content of framebuffer

Upvotes: 2

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