What is stencil buffer OpenGL?

What is stencil buffer OpenGL?

Advanced-OpenGL/Stencil-testing. A stencil buffer (usually) contains 8 bits per stencil value that amounts to a total of 256 different stencil values per pixel. We can set these stencil values to values of our liking and we can discard or keep fragments whenever a particular fragment has a certain stencil value.

Why wasnt there a Portal 3?

Finally, here’s the cold hard truth: Valve doesn’t need to make Portal 3 because the fans are keeping the franchise alive without them. In 2011, Valve released a Portal 2 level editor. In short, there’s no need to wait on Valve if you want more Portal. Download one of the various fan creations and start playing today.

Can a stencil be used to draw a portal?

A pair of shaders will use the stencil. We’ll draw the portal surface mesh initially using a block-colour shader which also writes a reference value to the stencil buffer – a unique value for each portal surface.

How does a stencil provide a reference value?

Inside the stencil, we provide a reference value using the Ref keyword. In our case, we’ll want to use the _MaskID property as our reference value. The stencil uses a comparison function, Comp, to determine whether it should render a pixel by comparing the value already in the stencil buffer to the reference value.

Is the stencil the same size as the framebuffer?

Recall from previous discussions that the stencil buffer is the same size as the framebuffer (i.e. the image), and it contains a value of zero inside each pixel by default. Inside the stencil, we provide a reference value using the Ref keyword. In our case, we’ll want to use the _MaskID property as our reference value.

How does the always function work in stencil?

The stencil uses a comparison function, Comp, to determine whether it should render a pixel by comparing the value already in the stencil buffer to the reference value. In our case, we’re using the Always function, which means the pixel will be drawn regardless of the stencil value (and provided it passes a depth test too).