问题描述
如何发送到 MAT4 类型的着色器属性?
how to send to a shader attribute with the MAT4 type?
attribute mat4 attr;
...
JS:
var attr=gl.getAttribLocation(_program,"attr");
推荐答案
来自规范第 2.10.4 节
当一个属性变量被声明为 mat4
时,它的矩阵列取自通用属性的 (x, y, z, w) 分量 i通过 i + 3.
所以
JS:
var row0Location = gl.getAttribLocation(_program, "attr");
var row1Location = row0Location + 1;
var row2Location = row0Location + 2;
var row3Location = row0Location + 3;
至于获取数据,最常见的方法是将所有矩阵放在一个缓冲区中
As for getting the data the most common way would be to put all the matrices in one buffer so
var matrices = new Float32Array(numMatrices * 16);
... // fill out your matrices
gl.bufferData(gl.ARRAY_BUFFER, matrices, gl.STATIC_DRAW);
然后设置属性
var floatsPerRow = 4
var bytesPerRow = floatsPerRow * 4;
var bytesPerMatrix = bytesPerRow * 4;
var row0Offset = bytesPerRow * 0;
var row1Offset = bytesPerRow * 1;
var row2Offset = bytesPerRow * 2;
var row3Offset = bytesPerRow * 3;
gl.enableVertexAttribArray(row0Location);
gl.vertexAttribPointer(row0Location, floatsPerRow, gl.FLOAT,
false, bytesPerMatrix, row0Offset);
gl.enableVertexAttribArray(row1Location);
gl.vertexAttribPointer(row1Location, floatsPerRow, gl.FLOAT,
false, bytesPerMatrix, row1Offset);
gl.enableVertexAttribArray(row2Location);
gl.vertexAttribPointer(row2Location, floatsPerRow, gl.FLOAT,
false, bytesPerMatrix, row2Offset);
gl.enableVertexAttribArray(row3Location);
gl.vertexAttribPointer(row3Location, floatsPerRow, gl.FLOAT,
false, bytesPerMatrix, row3Offset);
需要注意的事情.如果您正在调试并在着色器中注释掉 attr
,则 row0Location
将是 -1 并使用一个调用所有 gl.vertexAttrib
函数-1 位置是无操作的,这很好.但是,因为您计算其他位置 row1Location
,row2Location
和 row3Location
将是有效的属性位置,就 WebGL 而言,但就WebGL 而言是无效的你的程序有问题.没什么大不了的,只是要记住.
Something to be aware of. If you're debugging and you comment out attr
in your shader then row0Location
will be -1 and calling all the gl.vertexAttrib
functions with a -1 location is a no-op which is good. But, because you compute the other locations row1Location
, row2Location
and row3Location
will be valid attribute locations as far as WebGL is concern but invalid as far as your program is concerned. Not a big deal just something to keep in mind.
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