very slow on raspberry pi 4 (64 bit)

[kiai72]

Hello on Raspberry Pi OS (64 bit) (2.1.1. from the official repository) it's unplayable slow.

why ? other games like supertuxkart work fine.

[juzzlin]

My guess is that there might be no HW acceleration on Raspberry Pi for framebuffer blitting that is being used in renderer.cpp:

QOpenGLFramebufferObject::blitFramebuffer(m_shadowFbo.get(), m_fbo.get(), GL_DEPTH_BUFFER_BIT);

[kiai72]

But why only with this game. Supertuxkart for example works fast.

[juzzlin]

But why only with this game. Supertuxkart for example works fast.

That's because SuperTuxCart and other games very likely don't use framebuffer blitting at all. In Dust Racing 2D it's being used to create those fake 3D shadows. I'm only guessing that it could be the reason.

[kiai72]

ok, is there a flag to turn this feature off ?

[juzzlin]

Try this out: 596a0f1

[juzzlin]

Build with -DDisableFramebufferBlits=ON and it will render the shadows directly to the target framebuffer. The only downside is that they will be pretty bad. However, if this fixes the performance issue on Raspberry Pi I could try to improve that method.

[kiai72]

i build with
cmake ../.. -DDisableFramebufferBlits=OFF
make

but it does not change anything. still unplayable slow. Or do i have to set a flag in .conf as well ?

[juzzlin]

i build with cmake ../.. -DDisableFramebufferBlits=OFF make

but it does not change anything. still unplayable slow. Or do i have to set a flag in .conf as well ?

Should be -DDisableFramebufferBlits=ON. I made a typo in my earlier comment, but immediately fixed it :)

[kiai72]

i tried with -DDisableFramebufferBlits=ON as well (+ another make) -> no change!

not only the game is slow - even the menu is very slow.

[juzzlin]

Stupid question, but did you update the source code from master branch so that it actually included my framebuffer hack in commit 596a0f1 ?

If yes, then the root cause for the slowness must be something else and needs more investigation.

[kiai72]

after you wrote about this new feature i downloaded the master as zip ...

[kiai72]

so can we please add more switches that simplify the graphics - to make it run on rpi4 ?