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OGL: Work around slowdown of glMapBufferRange with SSBO on NVIDIA drivers

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Using glMapBufferRange to read back the contents of the SSBO is extremely
slow on NVIDIA drivers. This is more noticeable at higher internal
resolutions. Using glGetBufferSubData instead does not seem to exhibit
this slowdown.
This commit is contained in:
Stenzek
2016-05-11 22:19:59 +10:00
parent 24ea2dc2da
commit 89e54fbd6c
3 changed files with 27 additions and 4 deletions
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22
Source/Core/VideoBackends/OGL/BoundingBox.cpp
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@ -6,6 +6,7 @@
#include "VideoBackends/OGL/BoundingBox.h"
#include "VideoCommon/DriverDetails.h"
#include "VideoCommon/VideoConfig.h"
static GLuint s_bbox_buffer_id;
@ -42,12 +43,25 @@ int BoundingBox::Get(int index)
{
int data = 0;
glBindBuffer(GL_SHADER_STORAGE_BUFFER, s_bbox_buffer_id);
void* ptr = glMapBufferRange(GL_SHADER_STORAGE_BUFFER, index * sizeof(int), sizeof(int), GL_MAP_READ_BIT);
if (ptr)
if (!DriverDetails::HasBug(DriverDetails::BUG_SLOWGETBUFFERSUBDATA))
{
data = *(int*)ptr;
glUnmapBuffer(GL_SHADER_STORAGE_BUFFER);
// Using glMapBufferRange to read back the contents of the SSBO is extremely slow
// on nVidia drivers. This is more noticeable at higher internal resolutions.
// Using glGetBufferSubData instead does not seem to exhibit this slowdown.
glGetBufferSubData(GL_SHADER_STORAGE_BUFFER, index * sizeof(int), sizeof(int), &data);
}
else
{
// Using glMapBufferRange is faster on AMD cards by a measurable margin.
void* ptr = glMapBufferRange(GL_SHADER_STORAGE_BUFFER, index * sizeof(int), sizeof(int), GL_MAP_READ_BIT);
if (ptr)
{
memcpy(&data, ptr, sizeof(int));
glUnmapBuffer(GL_SHADER_STORAGE_BUFFER);
}
}
glBindBuffer(GL_SHADER_STORAGE_BUFFER, 0);
return data;
}