Shader is running really slow. Not sure what it is.

[Azaral]

I think I found the problem in your code. I just made a change and it runs at max resoltuion at over 175fps. Will follow up with a post in a few minutes showing the problem I found.

[Azaral]

The problem section is here

texture = renderTexture.getTexture();
sprite.setTexture(texture);
 

You are copying a texture and then setting this in the sprite and then drawing the sprite.

I instead did this outside of the while loop

sprite.setTexture(renderTexture.getTexture());
 

Then this section

Window.clear(sf::Color::Black);
testShader.setParameter("resolution",100,100);
testShader.setParameter("time",time1.getElapsedTime().asSeconds());
renderTexture.clear();
renderTexture.draw(testShape,&testShader);
renderTexture.display();
texture = renderTexture.getTexture();
sprite.setTexture(texture);
Window.draw(sprite);
Window.display();
 

became this

Window.clear(sf::Color::Black);
testShader.setParameter("resolution",1280,720);
testShader.setParameter("time",time1.getElapsedTime().asSeconds());

renderTexture.clear();
renderTexture.draw(testShape,&testShader);
renderTexture.display();

Window.draw(sprite);
Window.display();
 

The main problem was you were copying a texture, which is a heavy weight operation, and in this case completely unnecessary. The sprite just needs it's texture set once as the sprite contains a pointer to its texture. Copying the texture was unnecessary since you can just set the sprite's texture to be the texture inside the render texture and then any changes will automatically be taken into account when you draw the sprite since the sprite points to the texture inside the render texture.

With these changes it runs silky smooth at ~180 fps on my machine, which is ~5 years old. The graphics card is an nvidia 8800 GTX

[dixondean25]

That was the problem, I'm getting great fps now. I will admit this was my first time using sf::RenderTexture, and I didn't know you only need to call it once. Thank you so much Azaral you're friggin' awesome.

[Azaral]

I try to be and occasionally I succeed.

Also, I tested it and you do not need the sf::RectangleShape here

 renderTexture.draw(testShape,&testShader);
 

I did this instead and it works near as I can tell

renderTexture.draw(sprite,&testShader);
 

[dixondean25]

I try to be and occasionally I succeed.

Also, I tested it and you do not need the sf::RectangleShape here

 renderTexture.draw(testShape,&testShader);
 

I did this instead and it works near as I can tell

renderTexture.draw(sprite,&testShader);
 

yes this also works. thank you again!