EXT_shader_texture_lod

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EXT_shader_texture_lod 扩展属于 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 使用扩展在 WebGL 教程 .

可用性： This extension is only available to WebGL1 contexts. In WebGL2 , the functionality of this extension is available on the WebGL2 context by default. It requires GLSL #version 300 es .

GLSL built-in functions

The following new functions can be used in GLSL shader code, if this extension is enabled:

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)

范例

Enabling the extensions:

gl.getExtension('EXT_shader_texture_lod');

Shader code that avoids artifacts when wrapping texture coordinates:

<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>

规范

规范	状态	注释
EXT_shader_texture_lod The definition of 'EXT_shader_texture_lod' in that specification.	推荐	初始定义。

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更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`EXT_shader_texture_lod`	Chrome Yes	Edge 17	Firefox 50	IE ?	Opera Yes	Safari ?	WebView Android Yes	Chrome Android Yes	Firefox Android ?	Opera Android Yes	Safari iOS ?	Samsung Internet Android Yes

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GLSL built-in functions

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