Texture streaming caches wrong size for movable static mesh

Hi there,

I’m seeing a bug in UE4.17.2 which appears to be there since UE4.15, which is that UStaticMeshComponent::GetStreamingTextureInfo will use GetTextureStreamingTransformScale() for movable meshes. The result of GetStreamingTextureInfo is cached, which means that a movable will have its texture streaming resolution set to be appropriate for whatever size the mesh had when MarkComponentsRenderStateDirty was last called. For meshes that get rescaled during play, this can lead to wildly wrong texture resolutions.

This bug likely also affects landscape grass if it is using rescaled meshes, because in that case, UInstancedStaticMeshComponent::GetTextureStreamingTransformScale will return 1, thus leading to textures that are streamed under the assumption that the grass meshes are rendered at their original scale.

Steps to reproduce:

In constructor, call SetActorScale3D(FVector(0.01))

In Tick, wait 0.1 seconds and then call SetActorScale3D(FVector(1.0))

Observed behavior:

The mesh will be rendered with only 1% of its original texture resolution streamed in.

Expected behavior:

The mesh will render with its original texture resolution.

Temporary ugly Workaround:

subclass UStaticMeshComponent and override GetTextureStreamingTransformScale to always return 1