dtclamp

Havok physics dt clamp for Watch Dogs (WD1). Clamps the per-frame physics delta-time to max 1/30s — prevents ragdoll, vehicle, and object glitches when running above 60fps.

Why

At high framerates, the game feeds the Havok physics world a very small delta time each frame. A single-frame hitch (e.g. after a shader compile, file load, or frame drop) can spike that delta and make physics explode. dtclamp clamps the per-frame delta to a maximum of 1/30s before it reaches the physics accumulator, keeping physics stable regardless of framerate.

How it works

dtclamp hooks the Havok world-step accumulator in Disrupt_b64.dll at RVA 0x021285A9:

addss xmm6, dword ptr [rbx + 0x758]   ; physics accumulator += delta-time

It rewrites that instruction as:

minss xmm6, [1/30]                    ; clamp delta-time to 1/30
addss xmm6, [rbx + 0x758]             ; original instruction
jmp  [return address]                 ; return

The hook is a 6-byte trampoline patch (addss xmm6,[rbx+0x758] = F3 0F 58 B3 58 07 00 00) with an embedded float for 1/30.

Build

make            # outputs bin/dtclamp.asi
make clean      # removes bin/

Requires: x86_64-w64-mingw32-g++ (MinGW cross-compiler).

Install

Copy bin/dtclamp.asi to the game bin/ directory alongside watch_dogs.exe.

Logging

dtclamp writes dtclamp.log next to the game executable. It logs:

• Whether the DLL was found
• The hook RVA and whether target bytes matched
• "HOOK INSTALLED OK" on success, or an error description

If you see ERROR: target bytes don't match addss xmm6,[rbx+0x758], your game build has a different RVA — send the log and your game version to the author.

Files

File	Purpose
dtclamp.cpp	Single-source C++23 DLL
Makefile	MinGW cross-compile + strip
LICENSE	MIT

License

MIT