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bugfix(w3d): Skip rivers that overflow the dynamic index buffer #3489

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bugfix(w3d): Skip rivers that overflow the dynamic index buffer #3489

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8 changes: 7 additions & 1 deletion Core/GameEngineDevice/Source/W3DDevice/GameClient/Water/W3DWater.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2738,10 +2738,16 @@ void WaterRenderObjClass::drawRiverWater(PolygonTrigger *pTrig)
static Bool doWobble = true;

if (m_disableRiver) return;

// TheSuperHackers @bugfix arcticdolphin 12/10/2026 Skip rivers that do not fit the 16 bit dynamic buffers.
const Int indexCount = (rectangleCount+1)*2*3;

@macroscopeapp macroscopeapp Bot Oct 12, 2026

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🟡 Medium Water/W3DWater.cpp:2743

Rivers with 21,846 points are skipped even though they generate only 65,532 indices, which fit in the 16-bit buffer. indexCount includes an extra quad, evaluates to 65,538, and triggers the early return; calculate it from the rectangleCount * 6 indices the loop writes.

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const Int indexCount = (rectangleCount+1)*2*3;
const Int indexCount = rectangleCount*2*3;
🤖 Copy this AI Prompt to have your agent fix this: 
In file @Core/GameEngineDevice/Source/W3DDevice/GameClient/Water/W3DWater.cpp around line 2743:

Rivers with 21,846 points are skipped even though they generate only 65,532 indices, which fit in the 16-bit buffer. `indexCount` includes an extra quad, evaluates to 65,538, and triggers the early return; calculate it from the `rectangleCount * 6` indices the loop writes.

@tintinhamans tintinhamans Oct 12, 2026

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The check mirrors the count requested from DynamicIBAccessClass, which is what wraps.

@macroscopeapp macroscopeapp Bot Oct 12, 2026

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The request should match the loop’s rectangleCount * 6 writes. At 21,846 points that is 65,532, which fits; the current extra six causes an unnecessary skip. Counts above that still return before the unsigned short constructor can wrap.

@tintinhamans tintinhamans Oct 12, 2026

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Matching the loop gains two points and makes a 3 point river lock zero indices.

@macroscopeapp macroscopeapp Bot Oct 12, 2026

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You're right—the direct replacement would zero-lock a 3-point river. The count needs to retain a six-index minimum while using rectangleCount * 6 for nonzero rectangles.

if (indexCount > 65535)
return;

m_drawingRiver = true;

//allocate 2 triangles per side with 3 indices per triangle
DynamicIBAccessClass ib_access(BUFFER_TYPE_DYNAMIC_DX8,(rectangleCount+1)*2*3);
DynamicIBAccessClass ib_access(BUFFER_TYPE_DYNAMIC_DX8,indexCount);
{
DynamicIBAccessClass::WriteLockClass lockib(&ib_access);
UnsignedShort *curIb = lockib.Get_Index_Array();
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