[Interest] How to pass data to\from GLSL compute shaders in Qt5?
Gleb "Crazy Sage" Igumnov
crazy.sage at gmail.com
Thu Jan 19 07:05:45 CET 2017
Hello. I'm trying to port my program that is using GL compute shaders to Qt and I can't understand, what is correct way to work with buffers.
I initialize and use buffers with following code:
> QOpenGLBuffer cull_ray_buffer;
> QOpenGLBuffer cull_face_buffer;
> QOpenGLBuffer cull_out_buffer;
>
> if(!cull_ray_buffer.create())
> {
> qDebug()<<"Can't create cull ray buffer";
> return false;
> }
> cull_ray_buffer.allocate(border_rays.size()*sizeof(QVector4D));//border_rays_ is QVector of QVector4D
>
> if(!cull_face_buffer.create())
> {
> qDebug()<<"Can't create cull face buffer";
> return false;
> }
> cull_face_buffer.allocate(faces_.data(), faces_.size()*sizeof(QVector4D));//faces_ is QVector of QVector4D
>
> if(!cull_out_buffer.create())
> {
> qDebug()<<"Can't create cull out buffer";
> return false;
> }
> cull_out_buffer.allocate(tmp_out.data(), tmp_out.size()*sizeof(int));//tmp_out_ is QVector of int
>
> ogl->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, cull_ray_buffer.bufferId());//ogl is an instance of QOpenGLFunctions_4_4_Core
> ogl->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, cull_face_buffer.bufferId());
> ogl->glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 2, cull_out_buffer.bufferId());
In my shader I have buffers declared like this:
> layout(std430, binding=0) buffer rays{
> vec4 r[];
> };
>
> layout(std430, binding=1) buffer faces{
> vec4 f[];
> };
>
> layout(std430, binding=2) buffer outputs{
> int o[];
> };
I link shader before creating and binding buffers and then try to get output data by doing one of following things:
> int* b = static_cast<int*>(cull_out_buffer.map(QOpenGLBuffer::ReadOnly));
or
> cull_out_buffer.read(0,tmp_out.data(), tmp_out.size()*sizeof(int))
in first case I'm getting NULL pointer, in second - function returns false.
Also I'm not even sure that shader receives input data correctly (and I don't see any way to check it, because it is console gpu-computing project without any actual rendering).
Can someone please explain to me, what is correct way of passing data
to compute shaders using QOpenGLBuffer (if there is any)?
--
With best regards,
Gleb "Crazy Sage" Igumnov mailto:crazy.sage at gmail.com
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