glsl限定符

glsl限定符

Attribute

Vertex attribute data.

Example

attribute vec4 v_color;

Description

attribute read-only variables containing data shared from WebGL/OpenGL environment to the vertex shader.

Because the vertex shader is executed one time for each vertex, attributes are specify per vertex data typically with information such as: space position, color, normal direction and texture coordinates of a vertex.

Const

Constant qualifier

Example

const float PI = 3.14159265359;

Description

const qualifier can be applied to the declaration of any variable to specify that its value will not be changed.

Uniform

Uniform variable qualifier.

Example

uniform vec4 direction;

Description

uniform variables contain read-only data shared from WebGL/OpenGL environment to a vertex or fragment shader.

The value is per primitive, so is useful for variables which remain constant along a primitive, frame or scene.

Varying

Varying variable qualifier.

Example

varying vec3 position;

Description

varying variables contain data shared from a vertex shader to a fragment shader.

The variable must be written in the vertex shader and the read-only value in the fragment shader is then interpolated from the vertices which make up the fragment.

precision

highp

mediump

in

out

inout