Minimum distance in inverse distance attenuation and reflection produces NaN or weird output buffers

[dkotd]

System Information

• Steam Audio version: 4.5.2
• Operating System and version: Windows 11

Issue Description When I enable inverse distance attenuation with minDistance = 0.0f and reflection mode at the same time, iplReflectionEffectApply returns an output buffer with NaN values. When minDistance = 0.01f, the output buffer of the reflection sounds incredibly loud.

• Should I not be setting minDistance to any value less than a specific threshold when I have reflection enabled?
• In general, should I not be using inverse distance attenuation and reflection at the same time?

Sample Code

IPLSimulationInputs inputs {};
inputs.flags = IPLSimulationFlags(IPL_SIMULATIONFLAGS_DIRECT | IPL_SIMULATIONFLAGS_REFLECTIONS);

inputs.directFlags = IPL_DIRECTSIMULATIONFLAGS_DISTANCEATTENUATION;
IPLDistanceAttenuationModel model {};
model.type = IPL_DISTANCEATTENUATIONTYPE_INVERSEDISTANCE;
model.minDistance = 0.0f;
inputs.distanceAttenuationModel = model;

...

iplReflectionEffectApply(reflectionEffect, &params, &inBuff, &outBuff, nullptr); // outBuff has NaN

[lakulish]

The inverse-distance attenuation model implemented in Steam Audio does the following:

return 1.0f / std::max(distance, minDistance);

So if minDistance is very small, the computed value is very large (as you can see when minDistance is set to 0.01). In particular, when minDistance is 0, and distance also becomes 0, then the expression evaluates to infinity, so we want minDistance > 0. This has to do with the fact that true point sources cannot physically exist in the real world.