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What is stencil buffer in 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.
What is bitplane in OpenGL?
A buffer that stores a single bit of information about pixels is called a bitplane. As shown in Figure 10-1, the lower-left pixel in an OpenGL window is pixel (0, 0), corresponding to the window coordinates of the lower-left corner of the 1 ´ 1 region occupied by this pixel.
What is stencil shader unity?
In Unity, you can use a stencil buffer to flag pixels, and then only render to pixels that pass the stencil operation. See in Glossary on the GPU. The stencil buffer stores an 8-bit integer value for each pixel. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel.
How does the stencil buffer work in OpenGL?
The stencil buffer is an optional extension of the depth buffer that gives you more control over the question of which fragments should be drawn and which shouldn’t. Like the depth buffer, a value is stored for every pixel, but this time you get to control when and how this value changes and when a fragment should be drawn depending on this value.
Which is faster, a stencil or a scissor test?
Yes, scissor test can be faster can stencil because it’s a simple accept/reject based on a fragment’s screen space coords, whereas stencil needs to compare with the current value in the stencil buffer, possibly increment or decrement that current value, also take into account the results of the depth test, and so on.
What happens if you fail the stencil test?
Note that if the depth test fails, the stencil test no longer determines whether a fragment is drawn or not, but these fragments can still affect values in the stencil buffer! To get a bit more acquainted with the stencil buffer before using it, let’s start by analyzing a simple example.
What’s the purpose of the glscissor in OpenGL?
That’s where scissor in comes in. glScissor () defines a screen space rectangle beyond which nothing is drawn (if the scissor test is enabled). So for example, the following code will clear the whole screen, even though the viewport is set to a small portion of the larger window: