Influence and the restored world

Shaun White Skateboarding draws its city in two states, a grey Ministry state and a coloured restored one. A texture of the world, the influence texture, says per place how restored it is, and materials choose how to react. Observed

The influence texture in the shaders

The shared shader source ekinfluencecommon.hlsl reads the alpha channel of an InfluenceSampler, maps the world X and Y position to texture coordinates through g_InfluenceTextureOriginScale, and blends the colour-control result of the uninfluenced state with that of the influenced state by the sampled value. The same source can discard pixels. With the define KILL_UNINFLUENCED_PIXEL alone a pixel is clipped when the influence minus 0.01 is negative, that is where the world is not restored. With INVERSE_KILL_UNINFLUENCED_PIXEL as well it is clipped when 1 minus (the influence plus 0.01) is negative, that is where the world is restored. With neither define nothing is clipped. Observed

Material hide mode

The SKGenericMaterial field InfluenceHidePixelMode (a u32 at body offset 525, property hash 0x7DACF81C) is an enum whose names are HideNone 0, HideBefore 1 and HideAfter 2. The engine’s key generation for a material sets the shader define KILL_UNINFLUENCED_PIXEL when the mode is not 0 and INVERSE_KILL_UNINFLUENCED_PIXEL when it is 2, so HideNone materials generate neither. Observed

Over the five materials of the metal trees and tree lights examined in level 01 the mode is 0. A decal of the Ministry logo tile floor stores 2: in the restored state the original discards every pixel of it. Seventy-seven of the 95 decal-named blended materials of the six levels store 1, as do water fountains, so the field is the restoration pixel kill, not a decal marker. Observed

The display option

The renderer keeps a view object whose embedded DisplayOptions (type hash 0x1C0637AB, 254 bytes, started at view offset 0x1C) holds InfluenceMode at options offset 0x4C (property hash 0xB70D77EF, view offset 0x68). The enum is NormalInfluence 0, NoInfluence 1 and FullyInfluenced 2. The neighbouring enums are the render mode at 0x44 and the fill mode at 0x50. The view is the pointer at offset 0x88 of the renderer; in the recorded build the renderer’s view is also reached as [[0x1C9C7EC]+0x1F8]. Observed

The influence pass caches its influence binding: it has an initialised byte at offset 0x14, and the initialisation routine runs once per pass instance when that byte is 0. Changing the mode alone therefore does not change the picture; clearing the byte, as the engine’s own reset does, makes the pass re-initialise on the next frame and bind the full-influence texture in mode 2. A pass instance is constructed on a stack in the renderer’s caller, so the byte caches per instance, not proven per level. Observed

Mode 2 restores the colours and shading of the world but not the trees, which grow in response to a separate event. Observed