紧跟着this教程的转换反馈,但是在python中。给定一个简单的变换反馈顶点着色器
#version 400 core
in float inValue;
out float outValue;
void main()
{
outValue = 5*inValue+6;
}
以及周围的python代码来调用它
...
varyings = ctypes.create_string_buffer('outValue')
varyings_pp = POINTER(POINTER(c_char))(ctypes.cast(varyings, POINTER(c_char)))
gl.glTransformFeedbackVaryings(program, 1, varyings_pp, gl.GL_INTERLEAVED_ATTRIBS);
gl.glLinkProgram(program)
gl.glUseProgram(program)
vao = gl.glGenVertexArrays(1)
gl.glBindVertexArray(vao)
data = np.array([1.,2.,3.,4.,5.], dtype=np.float32)
vbo = gl.glGenBuffers(1)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, vbo)
gl.glBufferData(gl.GL_ARRAY_BUFFER, data.nbytes, data, gl.GL_STATIC_DRAW)
inputAttrib = gl.glGetAttribLocation(program, "inValue")
gl.glEnableVertexAttribArray(inputAttrib)
gl.glVertexAttribPointer(inputAttrib, 1, gl.GL_FLOAT, gl.GL_FALSE, 0, 0)
data = np.array([-1.,-2.,-3.,-4.,-5.], dtype=np.float32)
tbo = gl.glGenBuffers(1)
gl.glBindBuffer(gl.GL_TRANSFORM_FEEDBACK_BUFFER, tbo)
gl.glBufferData(gl.GL_TRANSFORM_FEEDBACK_BUFFER, data.nbytes, data, gl.GL_STATIC_READ)
gl.glEnable(gl.GL_RASTERIZER_DISCARD)
gl.glBindBufferBase(gl.GL_TRANSFORM_FEEDBACK_BUFFER, 0, tbo)
gl.glBeginTransformFeedback(gl.GL_POINTS)
gl.glDrawArrays(gl.GL_POINTS, 0, 3)
gl.glEndTransformFeedback()
gl.glFlush()
r_data = np.empty_like(data)
gl.glGetBufferSubData(gl.GL_TRANSFORM_FEEDBACK_BUFFER, 0, data.nbytes, r_data)
print r_data
我得到输出[6. 6. 6. -4. -5.]
。因此inValue
似乎一直是0。但是,如果我读回GL\u ARRAY\u缓冲区,就会得到输入数据。我是否错误地将缓冲区绑定到顶点数组?在任何时候都不会引发任何glError
,并且着色器没有编译错误(出于美观目的,错误检查代码被省略)。你知道吗
解决方案简单,并且由于动态键入而容易遗漏。这条线在这里
应该读
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