EXT_shader_texture_lod extension
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
The EXT_shader_texture_lod extension is part of the WebGL API and adds additional texture functions to the OpenGL ES Shading Language which provide the shader writer with explicit control of LOD (Level of detail).
WebGL extensions are available using the WebGLRenderingContext.getExtension() method. For more information, see also Using Extensions in the WebGL tutorial.
GLSL built-in functions
The following new functions can be used in GLSL shader code, if this extension is enabled:
c
vec4 texture2DLodEXT(sampler2D sampler, vec2 coord, float lod)
vec4 texture2DProjLodEXT(sampler2D sampler, vec3 coord, float lod)
vec4 texture2DProjLodEXT(sampler2D sampler, vec4 coord, float lod)
vec4 textureCubeLodEXT(samplerCube sampler, vec3 coord, float lod)
vec4 texture2DGradEXT(sampler2D sampler, vec2 P, vec2 dPdx, vec2 dPdy)
vec4 texture2DProjGradEXT(sampler2D sampler, vec3 P, vec2 dPdx, vec2 dPdy)
vec4 texture2DProjGradEXT(sampler2D sampler, vec4 P, vec2 dPdx, vec2 dPdy)
vec4 textureCubeGradEXT(samplerCube sampler, vec3 P, vec3 dPdx, vec3 dPdy)
Examples
Enabling the extensions:
js
gl.getExtension("EXT_shader_texture_lod");
Shader code that avoids artifacts when wrapping texture coordinates:
html
<script type="x-shader/x-fragment">
#extension GL_EXT_shader_texture_lod : enable
#extension GL_OES_standard_derivatives : enable
uniform sampler2D myTexture;
varying vec2 texCoord;
void main(){
gl_FragColor = texture2DGradEXT(myTexture, mod(texCoord, vec2(0.1, 0.5)),
dFdx(texCoord), dFdy(texCoord));
}
</script>
Specifications
| Specification |
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| WebGL EXT_shader_texture_lod Khronos Ratified Extension Specification |
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Legend
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