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Size bgfx render-item arrays dynamically instead of reserving the maximum #1806

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Size bgfx render-item arrays dynamically instead of reserving the maximum #1806

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0e64f84
Size bgfx render-item arrays dynamically instead of reserving the max…
bghgary Jul 30, 2026
cb95893
Correct the numDrawCalls = 0 comment
bghgary Jul 30, 2026
89b3ebb
Start at 4096 draw calls and make the starting capacity configurable
bghgary Jul 30, 2026
81d6a59
Use BGFX_CONFIG_DRAW_CALL_BLOCK as the reserved-capacity knob
bghgary Jul 31, 2026
be3b4bf
Trim the numDrawCalls comment
bghgary Jul 31, 2026
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14 changes: 14 additions & 0 deletions Core/Graphics/Source/DeviceImpl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,20 @@ namespace Babylon::Graphics
auto& init = m_state.Bgfx.InitState;
init.callback = &m_bgfxCallback;

// bgfx reserves limits.numDrawCalls render-item slots (sort keys, RenderItem,
// RenderBind) up front for every Frame, and defaults to
// BGFX_CONFIG_MAX_DRAW_CALLS (65535) -- tens of megabytes.
//
// 0 asks for a single BGFX_CONFIG_DRAW_CALL_BLOCK instead (4096, set in
// Dependencies/CMakeLists.txt), and bgfx resizes in block steps up to that same
// ceiling. Growth is reactive -- the frame that overflows drops the draws past
// capacity -- so the block should sit above the expected peak.
//
// numDrawCallPeakFrames is the shrink delay in frames, ~1s at 60fps. Resizing
// is disabled entirely at 0.
init.limits.numDrawCalls = 0;
init.limits.numDrawCallPeakFrames = 60;

// Use the noop renderer if the configuration has no window and no size.
if (config.Window == WindowT{} && config.Width == 0 && config.Height == 0)
{
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1 change: 1 addition & 0 deletions Dependencies/CMakeLists.txt
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Expand Up @@ -46,6 +46,7 @@ FetchContent_MakeAvailable_With_Message(bgfx.cmake)
target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_DEBUG_ANNOTATION=0)

target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_DEFAULT_MAX_ENCODERS=2)
target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_DRAW_CALL_BLOCK=4096)
target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_MAX_VERTEX_STREAMS=18)
target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_MIN_RESOURCE_COMMAND_BUFFER_SIZE=16)
target_compile_definitions(bgfx PRIVATE BGFX_CONFIG_MIN_UNIFORM_BUFFER_SIZE=4096)
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