glGetShaderPrecisionFormat 3G
glGetShaderPrecisionFormat return the range and precision for different shader numeric formats

## C Specification

void `glGetShaderPrecisionFormat` GLenum shaderType GLenum precisionType GLint *range GLint *precision

## Parameters

shaderType

  Specifies the type of shader to query. Must be either `GL_VERTEX_SHADER` or `GL_FRAGMENT_SHADER`.

precisionType

  Specifies the numeric format to query, corresponding to a shader precision qualifier and variable type. Must be one of `GL_LOW_FLOAT`, `GL_MEDIUM_FLOAT`, `GL_HIGH_FLOAT`, `GL_LOW_INT`, `GL_MEDIUM_INT`, or `GL_HIGH_INT`.

range

  Specifies a pointer to the two-element array in which the log 2 of the minimum and maximum representable magnitudes of the format are returned.

precision

  Specifies a pointer to the location in which the log 2 of the precision of the format is returned.

## Description

`glGetShaderPrecisionFormat` returns range and precision limits for floating-point and integer shader variable formats with low, medium, and high precision qualifiers. When minRep and maxRep are the minimum and maximum representable values of the format, floor ⁡ log 2 ⁡ minRep and floor ⁡ log 2 ⁡ maxRep are returned in range as the first and second elements, respectively.

If the smallest representable value greater than 1 is 1 + ε then floor ⁡ - log 2 ⁡ ε is returned in precision. An integer format will have an ε of 1, and thus will return 0. Floating-point formats will return values greater than 0.

## Notes

The minimum range and precision required for different formats is described in the OpenGL ES Shading Language Specification.

If a high precision floating-point format is not supported for fragment shaders, calling `glGetShaderPrecisionFormat` with arguments `GL_FRAGMENT_SHADER` and `GL_HIGH_FLOAT` will return 0 for both range and precision. Support for a high precision floating-point format is mandatory for vertex shaders.

Shader compiler support is optional, and thus must be queried before use by calling glGet with argument `GL_SHADER_COMPILER`. glShaderSource, glCompileShader, `glGetShaderPrecisionFormat`, and glReleaseShaderCompiler will each generate `GL_INVALID_OPERATION` on implementations that do not support a shader compiler. Such implementations instead offer the glShaderBinary alternative for supplying a pre-compiled shader binary.

If an error is generated, no change is made to the contents of range or precision.

## Errors

`GL_INVALID_OPERATION` is generated if a shader compiler is not supported.

`GL_INVALID_ENUM` is generated if shaderType or precisionType is not an accepted value.

## Associated Gets

glGet with argument `GL_SHADER_COMPILER`

## See Also

glCompileShader, glShaderSource

## Copyright

Copyright 2008 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.