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How many times is the fragment shader called?
The fragment shader is executed at least once per rendered fragment. If multisampling is used, it may be executed once per fragment or once per sample, depending upon whether the shader references gl_SamplePosition.
What is a fragment shader vs vertex?
One main difference is that a vertex shader can manipulate the attributes of vertices. which are the corner points of your polygons. The fragment shader on the other hand takes care of how the pixels between the vertices look. They are interpolated between the defined vertices following specific rules.
What means shader?
In computer graphics, a shader is a type of computer program originally used for shading in 3D scenes (the production of appropriate levels of light, darkness, and color in a rendered image). Shaders are used widely in cinema post-processing, computer-generated imagery, and video games to produce a range of effects.
How many times a fragment shader is executed?
A Fragment shader will be executed for those fragments even though they might merged/discarded later. I don’t know a way give you exact number of the fragments in a scene, maybe there is a tool for NVidia or ATI than can give you how many times a fragment shader is executed.
How are input variables interpolated in fragment shader?
The user-defined inputs received by this fragment shader will be interpolated according to the interpolation qualifiers declared on the input variables declared by this fragment shader. The fragment shader’s input variables must be declared in accord with the interface matching rules between shader stages.
Where do I find the fragment shader in OpenGL?
Specifically, between this stage and the last Vertex Processing shader stage in the program or pipeline object. Fragment Shader s have the following built-in input variables. The location of the fragment in window space. The X, Y and Z components are the window-space position of the fragment.
How often is shader called for each pixel?
So basically it is called once for each pixel. If you are interested for more exact numbers, you could use shader atomics to test specific cases. Here are some links about the usage of shader atomic counters.