Point cloud flags

[Farsthary]

Hi, which are the flags for rendering a point clouds using BGFX?
uint64_t state = 0
| BGFX_STATE_WRITE_R
| BGFX_STATE_WRITE_G
| BGFX_STATE_WRITE_B
| BGFX_STATE_PT_POINTS;

Since point clouds does not need indices information, I get random crashes and freezes using bgfx if I leave the index buffer at 0.

`renderer_d3d11.cpp (3838): BGFX CHECK device->CreateBuffer(&desc , 0 , &m_ptr ) FAILED 0x80070057

Exception thrown at 0x00007FFCFE514B59 in Rah.exe: Microsoft C++ exception: _com_error at memory location 0x000000B84B7DE240.`

I do not want to create a costly index buffer just to render points. What are the alternatives?

[pezcode]

That's actually a bug, what you're trying to do works on the other backends.

For reference:

bgfx/src/renderer_d3d11.cpp

Line 6252 in 9ec2472

uint32_t numVertices = draw.m_numVertices;

draw.m_numVertices can be UINT32_MAX at which point the vertex count needs to be limited by the vertex buffer size. There's code that does this already:

bgfx/src/renderer_d3d11.cpp

Line 6186 in 9ec2472

numVertices = bx::uint32_min(UINT32_MAX == draw.m_numVertices

just have to propagate numVertices to the relevant place. I can send a PR with a fix later today or tomorrow.

[bkaradzic]

Actually before fix, I would like repro. @Farsthary could you modify 01-cubes to cause issue you're seeing?

[pezcode]

You can reproduce this in 01-cubes by adding if (s_ptState[m_pt] != BGFX_STATE_PT_POINTS) before line 325 bgfx::setIndexBuffer(ibh);.

There'll be a few

Vertex Buffer at the input vertex slot 0 is not big enough for what the Draw*() call expects to traverse.

and on my machine, followed by DXGI_ERROR_DEVICE_HUNG and a crash after a second.

[Farsthary]

Thanks for the answers! sure, I will upload soon my original code and will check if the fix works.

[Farsthary]

Yes, basically the step to reproduce is what @pezcode did.
With BGFX_STATE_PT_POINTS by not setting and indexBuffer //bgfx::setIndexBuffer(ibh);
it becomes unresponsive and crashing/lagging.

[pezcode]

@Farsthary should be fixed with the latest commit b298851, see if that works for you and report back 🙏

[Farsthary]

AWESOME!!!!
it works now and no need to waste resources on indices for pure point clouds. Thanks a lot