问题描述

openscenegraph 3 cookbookz这本书的第八章的云的例子，懂得进来看看

const char* vertCode = {
    "uniform sampler2D defaultTex;n"
    "uniform int width;n"
    "uniform int height;n"
    "varying float brightness;n"
    "void main()n"
    "{n"
    " float row = float(gl_InstanceID) /
    float(width);n"
    " vec2 uv = vec2(fract(row), floor(row) /
    float(height));n"
    " vec4 texValue = texture2D(defaultTex, uv);n"
    // Read and specify the position data from texture
    " vec4 pos = gl_Vertex + vec4(texValue.xyz, 1.0);n"
    // Use alpha of the texel as the brightness value
    " brightness = texValue.a;n"
    " gl_Position = gl_ModelViewProjectionMatrix * pos;n"
    "}n"
};

什么意思？？？