java - opengl : loading array types to uniform buffer objects

Question

这是我在片段着色器中的统一块

layout (std140)   uniform Material
{
 float array[2];
};

这是统一块对象。我正在使用 LWJGL 2.9.3

  private UBO(int programID,String blockName)
  {
   blockID=GL31.glGetUniformBlockIndex(programID,blockName);  //Get index of uniform block
   
   IntBuffer indices=BufferUtils.createIntBuffer(16);
   GL31.glGetActiveUniformBlock(programID,blockID,GL31.GL_UNIFORM_BLOCK_ACTIVE_UNIFORM_INDICES,indices); //query all the indices of every variable in the uniform block
   indices.flip().limit(GL31.glGetActiveUniformBlocki(programID,blockID,GL31.GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS)); //the above method requires an int buffer of 16 even if i dont have 16 variables, but after retriving indices limit the buffer to read only actual number of variables
   while(indices.hasRemaining())
   {
    int variableIndex=indices.get();
   
    String name=GL31.glGetActiveUniformName(programID
                                           ,variableIndex
                                           ,GL31.glGetActiveUniformsi(programID,variableIndex,GL31.GL_UNIFORM_NAME_LENGTH)); //get the name of the variable
    
    int offset=GL31.glGetActiveUniformsi(programID,variableIndex,GL31.GL_UNIFORM_OFFSET); //query the offset[will use it in buffer sub data]
   
    offsets.put(name,offset);
   }
   
   
   GL15.glBindBuffer(GL31.GL_UNIFORM_BUFFER,bufferID=GL15.glGenBuffers());
   
   GL15.glBufferData(GL31.GL_UNIFORM_BUFFER
                    ,GL31.glGetActiveUniformBlocki(programID,blockID,GL31.GL_UNIFORM_BLOCK_DATA_SIZE)
                    ,GL15.GL_DYNAMIC_DRAW); //allocate buffer to the actual size of the uniform block
   
   GL15.glBindBuffer(GL31.GL_UNIFORM_BUFFER,0);
  }
  
  private void bufferData(String name,Buffer value)
  { 
   int offset=offsets.get(name); //update float or int arrays
   if(value instanceof FloatBuffer){GL15.glBufferSubData(GL31.GL_UNIFORM_BUFFER,offset,(FloatBuffer)value);}
   else{GL15.glBufferSubData(GL31.GL_UNIFORM_BUFFER,offset,(IntBuffer)value);}
  }

对于常规的非数组变量，它工作正常，但对于数组，浮点数和每个数组类型的值都加载不正确。我已经阅读了文档，指定数组中的每个元素都有 16[vec4 size] 对齐，但我不知道如何在我的代码中指定
更新浮点数组我只是使用

bufferData("array[0]",BufferUtils.createFloatBuffer(2).put(new float[]{10.5f,3.0f}).flip());
//the array[0] dosen't actually refer to only the first element of the array it is the name of the array returned by GL31.glGetActiveUniformName()

但同样，浮点数都加载不正确。

Answer 1

I have read the docs specifying that every element in the array has an 16[vec4 size] alignment but i don't know how to specify that in my code [...]

你是对的，你必须为每个元素添加 3 个浮点数来填充:

BufferUtils.createFloatBuffer(8).put(new float[]{10.5f,0.0f,0.0f,0.0f,3.0f,0.0f,0.0f,0.0f}).flip()

但是，我建议使用单个 vec2而不是 float array[2] :

layout (std140)   uniform Material
{
    vec2 array;
};

注意，在 GLSL 中，可以使用 Swizzling 访问 vector 数据类型的组件。或索引运算符(例如 array[0] 或 array[1] )。