Shader common params

Coordinate Spaces:

  • Camera Space: X+ gets mapped to Z+, Y+ gets mapped to X+, Z+ gets mapped to Y+. Basically Right handed Y-up

  • View Space: Same as camera space except in shadow rendering

  • PreViewTranslation/etc is confusing. Here’s the math:

  • ViewMatrix = PreViewTranslation * ViewRotationMatrix

  • It’s just separating out camera translation from rotation for accuracy

  • “Translated” prefix means camera relative space (aka 0,0,0 is camera position in world space) aka it’s WorldPos * TranslationMatrix(-CameraOrigin)

  • “PreViewTranslation” prefix just means before this translation happened so in actual world space

  • TranslatedWorldToCameraView = TranslatedWorldToView = TranslatedViewMatrix = Inverse of camera rotation matrix

TranslatedWorldCameraOrigin = 0,0,0 (post -vieworigin translation)

WorldCameraOrigin = Camera Position

WorldViewOrigin = Camera Position (different during shadow pass)

PreViewTranslation = -CameraPosition

  • TranslatedWorldToView = TranslatedViewMatrix

  • FMaterialPixelParameters

  • SvPosition: Like SV_Position (.xy is pixel position at pixel center, z:DeviceZ, .w:SceneDepth)

this is not relative to the current viewport. RelativePixelPosition = MaterialParameters.SvPosition.xy - View.ViewRectMin.xy;

  • ScreenPosition: Post projection position reconstructed from SvPosition, before the divide by W. left..top -1..1, bottom..top -1..1 within the viewport, W is the SceneDepth

  • WorldPosition_CamRelative: This is just absoluteworldposition - WorldCameraOrigin. Not rotation adjusted in viewspace

  • PreViewTranslation = -ViewOrigin

  • ViewRotationMatrix = FInverseRotationMatrix(ViewRotation) * ViewPlanesMatrix;

  • TranslatedViewMatrix = ViewRotationMatrix;

  • ViewMatrix = FTranslationMatrix(-ViewLocation) * ViewRotationMatrix;

  • WorldPosition_CamRelative => PixelPosWS - CameraOrigina1`

  • GetMaterialSharedSampler(Material.Texture2D_0Sampler,Material.Clamp_WorldGroupSettings)


Last update: November 14, 2019