Rendering Special Effects with Shaders - SFML Essentials - page 144

After we declare a RenderTexture variable, we have to call the RenderTex-
ture::create() method to actually make a valid render texture. The method takes
width and height parameters as well as an indicator if the render texture uses a depth buf-
fer. In this case, we are only rendering a single circle shape on it, so no depth buffer is re-
quired. The depth buffer allows us to discard any fragments (pixels) that are rendered be-
hind already existing fragments. As such, if we were rendering 3D models to a texture
(using OpenGL) we would probably want the depth buffer enabled. In this example our
single circle shape is with radius 16, so we want a texture with a width and height of
2xRadius = 32.
After we create our circle shape, we render it onto the texture. RenderTex-
ture::clear() resets each texel of the texture to the given color. The color argument
is optional though, with Color::Black being the default color. Next, we draw our
shape onto the texture with the RenderTexture::draw() method and finally display
everything that has been drawn so far. The RenderTexture::display() method
updates each pixel of the texture with everything that has been done to it since the last
time it was called.
Now that we have our texture ready, we can use it by getting the underlying Texture
object with RenderTexture::getTexture() . The method returns a reference to
the texture object stored as a field inside RenderTexture . In this case we opt to create
a sprite out of it, which we can use later on for any purpose that a sprite can be used for.