3/11/2024 0 Comments Tessellation stencils example![]() ![]() Therefore, if the color value is half-way between the two representable colors, then half of the pixels will be one color and half the other.ĭithering is enabled by enabling GL_DITHER. Dithering algorithms essentially fake a smooth gradient by varying which color is selected based on the position of the fragment. For low-precision image formats, a subtle gradation in floating-point values is rendered as several sharp and distinct bands.ĭithering can be used to avoid this banding. When dithering is disabled, which color is chosen is implementation-defined, but it is not allowed to depend on the fragment's position in the window. For a given image format precision and a given color value, there will be at most two colors that could be used for that color: the one from rounding up and one from rounding down. This only matters when writing floating-point values to Normalized Integer Image Formats. When a color is being written to a framebuffer image, the image may have less precision than the incoming value. If GL_FRAMEBUFFER_SRGB is currently enabled, then for each fragment color that is being written to an image with an sRGB colorspace image format, the RGB components of the color are converted from linear to sRGB. If the image being read from is in the sRGB colorspace and GL_FRAMEBUFFER_SRGB is currently enabled, then the color read for the blending operation will be converted to linear RGB before blending with the fragment color. The result of this blending operation is what will be written. Granted, earlier hardware probably did them early anyway, but without Image Load Store functionality, you would never be able to tell the difference (outside of improved performance).Īll operations are processed in the following order, for each fragment generated by the fragment shader:Įach of the colors in the fragment can be combined with the corresponding pixel color in the buffer that the fragment will be written to. OpenGL 4.2 or ARB_shader_image_load_store explicitly requires the pixel ownership test and scissor test to always be performed early, no matter what. For example, executing a discard in an early-test fragment shader will not stop the depth or stencil values from being updated (the update is considered part of the test, write masks notwithstanding), nor will it stop the occlusion query counter from being bumped. Therefore, operations done in the fragment shader that affect such writes will be effectively ignored. Also, all writes to these buffers will happen first. If it happens by explicit request of the fragment shader, then all of these operations will happen first. ![]() Or it can happen if the fragment shader explicitly requests it. It can happen as an implicit optimization, if OpenGL detects that the fragment shader's execution will not interfere with these tests. There are two circumstances when these operations can be performed before the fragment shader. The following operations are able to be performed before the fragment shader, under certain circumstances (and in the following order): However, it is possible for these to be performed before the fragment shader. The specification states that the per-sample processing operations take place after the Fragment Shader has executed. ![]()
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