# OpenGL Need help with SMAA T2X

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Hello guys, I'm trying to integrate SMAA T2X (in OpenGL) in my project.

I got the SMAA 1x working very fast. However, I'm struggling to make the SMAA T2X version to work.

I have a set of 2 framebuffers representing the "previous" and "current" neighbourhood blending pass, just like in the SMAA DX10 demo  (https://github.com/iryoku/smaa/tree/master/Demo/DX10).

The documentation of the shader tells to render the geometry using subpixel jitters (https://github.com/iryoku/smaa/blob/master/SMAA.hlsl). For this, I create a jittering matrix which I apply in this way

MVP = Projection * View * Model * JitteringMatrix;

glm::vec2 jitter = getJitter();
glm::mat4 jitter_mat = glm::translate(glm::mat4(), glm::vec3(2.0f * jitter.x / float(width_), 2.0f * jitter.y / float(height_), 0.0f));

the getJitter function returns the jittering depending on the current frame of SMAA

glm::vec2 jitters[] = {
glm::vec2(-0.25f,  -0.25f),
glm::vec2( 0.25f, 0.25f)
};
return jitters[frame_index_];

However, the jittering matrix seems to be moving some geometry of my scene a little too much. Some objects start to shake after I apply this matrix. But this shouldn't happen since the jittering matrix should move the geometry less than a pixel (subpixel) so it shouldn't be noticeable.

Here's a short video showing the problem. I don't really know if the jittering process is causing the problem or if I'm doing something wrong in another step.
Thank you very much for your help!

EDIT: I think I solved the error. I should multiply the jittering matrix on the left side (JitteringMatrix * P * V * M); doing this solved the problem. However at low framerates the whole image starts to jitter (only a bit), is this normal?

Edited by Sytto

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